Document and Entity Information	12 Months Ended
Document and Entity Information	Dec. 31, 2018 shares
Document and entity information [abstract]
Document Type	20-F
Amendment Flag	false
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY
Trading Symbol	IMOS
Entity Registrant Name	ChipMOS TECHNOLOGIES INC.
Entity Central Index Key	0001123134
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Ex Transition Period	false
Entity Common Stock, Shares Outstanding	727,264,797

Consolidated Statements of Comprehensive Income $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018 TWD ($) $ / shares	Dec. 31, 2018 USD ($) $ / shares	Dec. 31, 2017 TWD ($) $ / shares	Dec. 31, 2016 TWD ($) $ / shares
Statement [LineItems]
Revenue	$ 18,480,027	$ 603,725	$ 17,940,855	$ 18,387,593
Cost of revenue	(15,050,032)	(491,670)	(14,703,729)	(14,745,472)
Gross profit	3,429,995	112,055	3,237,126	3,642,121
Research and development expenses	(939,269)	(30,685)	(985,873)	(838,866)
Sales and marketing expenses	(53,451)	(1,746)	(64,397)	(72,918)
General and administrative expenses	(485,068)	(15,847)	(639,809)	(822,068)
Other operating income (expenses), net	147,514	4,819	692,834	90,306
Operating profit	2,099,721	68,596	2,239,881	1,998,575
Finance costs	(190,248)	(6,215)	(217,283)	(179,116)
Share of profit (loss) of associates	(300,101)	(9,804)	(179,491)	28,924
Other non-operating income (expenses), net	173,070	5,654	(310,691)	(147,948)
Profit before income tax	1,782,442	58,231	1,532,416	1,700,435
Income tax expense	(456,618)	(14,918)	(550,487)	(177,120)
Profit from continuing operations	1,325,824	43,313	981,929	1,523,315
Profit (loss) from discontinued operations \| $			1,814,953	(122,105)
Profit for the year	1,325,824	43,313	2,796,882	1,401,210
Other comprehensive income (loss) that will be reclassified to profit or loss in subsequent periods:
Exchange differences on translation of foreign operations	(51,077)	(1,668)	(232,652)	(200,280)
Share of other comprehensive income of associates that will be reclassified to profit or loss \| $			678
Net other comprehensive loss that will be reclassified to profit or loss in subsequent periods	(51,077)	(1,668)	(231,974)	(200,280)
Other comprehensive income (loss) that will not be reclassified to profit or loss in subsequent periods:
Other comprehensive income (loss) on remeasurements of defined benefit plans	(59,961)	(1,959)	50,838	(43,383)
Unrealized gain on valuation of equity instruments at fair value through other comprehensive income	85,022	2,778
Share of other comprehensive loss of associates that will not be reclassified to profit or loss	(2,687)	(88)	(124)	(133)
Income tax effect that will not be reclassified to profit or loss	(4,126)	(135)	(8,642)	7,375
Net other comprehensive income (loss) that will not be reclassified to profit or loss in subsequent periods	18,248	596	42,072	(36,141)
Other comprehensive loss for the year, net of income tax	(32,829)	(1,072)	(189,902)	(236,421)
Total comprehensive income (loss)	1,292,995	42,241	2,606,980	1,164,789
Profit (loss) attributable to:
Equity holders of the Company - Continuing operations	1,325,824	43,313	981,929	1,829,327
Equity holders of the Company - Discontinued operations \| $			1,814,953	(122,105)
Predecessors' interests \| $				(306,012)
Profit for the year	1,325,824	43,313	2,796,882	1,401,210
Total comprehensive income (loss) attributable to:
Equity holders of the Company - Continuing operations	1,292,995	42,241	1,079,672	1,788,878
Equity holders of the Company - Discontinued operations \| $			1,527,308	(318,077)
Predecessors' interests \| $				(306,012)
Total comprehensive income (loss)	$ 1,292,995	$ 42,241	$ 2,606,980	$ 1,164,789
Ordinary shares [member]
Basic earnings per share:
Equity holders of the Company - Continuing operations \| (per share)	$ 1.65	$ 0.05	$ 1.16	$ 2.13
Equity holders of the Company - Discontinued operations			2.14	(0.14)
Equity holders of the Company \| (per share)	1.65	0.05	3.30	1.99
Predecessors' interests				(0.35)
Total basic earnings per share \| (per share)	1.65	0.05	3.30	1.64
Diluted earnings per share:
Equity holders of the Company - Continuing operations \| (per share)	1.63	0.05	1.13	2.11
Equity holders of the Company - Discontinued operations			2.10	(0.14)
Equity holders of the Company \| (per share)	1.63	0.05	3.23	1.97
Predecessors' interests				(0.35)
Diluted earnings per share \| (per share)	1.63	0.05	3.23	1.62
American depositary share (each representing 20 common shares) [member]
Basic earnings per share:
Equity holders of the Company - Continuing operations \| (per share)	33.03	1.08	23.20	42.56
Equity holders of the Company - Discontinued operations			42.87	(2.84)
Equity holders of the Company \| (per share)	33.03	1.08	66.07	39.72
Predecessors' interests				(7.12)
Total basic earnings per share \| (per share)	33.03	1.08	66.07	32.60
Diluted earnings per share:
Equity holders of the Company - Continuing operations \| (per share)	32.59	1.06	22.68	42.21
Equity holders of the Company - Discontinued operations			41.93	(2.82)
Equity holders of the Company \| (per share)	32.59	1.06	64.61	39.39
Predecessors' interests				(7.06)
Diluted earnings per share \| (per share)	$ 32.59	$ 1.06	$ 64.61	$ 32.33

Consolidated Statements of Financial Position $ in Thousands, $ in Thousands	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)
Non-current assets
Available-for-sale financial assets			$ 20,890
Non-current financial assets at fair value through profit or loss	$ 11,471	$ 375
Non-current financial assets at fair value through other comprehensive income	174,357	5,696
Investment in associates	3,863,741	126,225	3,433,332
Non-current financial assets at amortized cost	99,103	3,237
Property, plant and equipment, net	16,819,621	549,481	15,265,311
Deferred tax assets	226,716	7,407	212,372
Refundable deposits	22,006	719	21,342
Other non-current financial assets			70,241
Other non-current assets	28,560	933	35,474
Total non-current assets	21,245,575	694,073	19,058,962
Current assets
Inventories	1,778,835	58,113	1,929,239
Current financial assets at amortized cost	169,168	5,526
Current contract assets	299,835	9,795
Accounts and notes receivable	4,747,288	155,090	4,015,734
Accounts receivable - related parties	140	5	11
Other receivables	63,037	2,059	56,716
Other receivables - related parties	3,131	102	4,534
Current tax assets	139,595	4,561	104,906
Prepayments	44,592	1,457	54,126
Cash and cash equivalents	4,642,522	151,667	8,035,714
Total current assets	11,888,143	388,375	14,200,980
Total assets	33,133,718	1,082,448	33,259,942
Capital and reserves
Issued capital	7,528,577	245,952	8,862,971
Capital surplus	6,263,553	204,625	6,271,448
Retained earnings
Legal reserve	1,469,170	47,996	1,166,517
Unappropriated retained earnings	3,602,663	117,696	2,815,966
Other reserve
Foreign currency translation reserve	14,516	474	65,593
Unrealized gain on valuation of available-for-sale financial assets			678
Unrealized gain on valuation of financial assets at fair value through other comprehensive income	106,898	3,492
Unearned employee awards	(1,701)	(56)	(54,570)
Treasury stock	(962,503)	(31,444)	(1,007,654)
Total equity	18,021,173	588,735	18,120,949
Non-current liabilities
Long-term bank loans	9,042,096	295,397	7,498,853
Long-term deferred revenue			24,898
Long-term lease obligations payable			18,057
Deferred tax liabilities	308,759	10,087	174,293
Net defined benefit liability, non-current	520,765	17,013	478,526
Guarantee deposits	1,092	35	1,371
Total non-current liabilities	9,872,712	322,532	8,195,998
Current liabilities
Current contract liabilities	1,432	47
Accounts payable	637,271	20,819	687,960
Accounts payable - related parties	347	11	226
Payables to contractors and equipment suppliers	1,516,735	49,550	713,313
Other payables	1,678,482	54,835	1,980,182
Other payables - related parties	218	7	36
Current tax liabilities	546,342	17,849	273,177
Current provisions	29,352	959	127,311
Receipts in advance	1,013	33	5,209
Other current liabilities	30,800	1,006	31,275
Current refund liabilities	32,627	1,066
Long-term lease obligations payable, current portion	17,792	581	11,785
Long-term bank loans, current portion	747,422	24,418	2,143,168
Short-term bank loans			969,353
Total current liabilities	5,239,833	171,181	6,942,995
Total liabilities	15,112,545	493,713	15,138,993
Total equity and liabilities	$ 33,133,718	$ 1,082,448	$ 33,259,942

Consolidated Statements of Changes in Equity $ in Thousands, $ in Thousands	TWD ($)	USD ($)	Issued capital [member] TWD ($)	Capital surplus [member] TWD ($)	Legal reserve [member] TWD ($)	Unappropriated retained earnings [member] TWD ($)	Foreign currency translation reserve [member] TWD ($)	Amounts recognized in other comprehensive income (loss) and accumulated in equity relating to non-current assets held for sale [member] TWD ($)	Unearned employee awards [member] TWD ($)	Treasury stock [member] TWD ($)	Treasury stock [member] USD ($)	Attributable to equity holders of the company total [member] TWD ($)	Equity attributable to predecessors' interests [member] TWD ($)	Unrealized gain (loss) in available-for-sale financial assets [member] TWD ($)	Unrealized gain on valuation of financial assets at fair value through other comprehensive income [member] TWD ($)
Beginning Balance at Dec. 31, 2015	$ 21,034,419		$ 8,962,066	$ 3,755,849	$ 914,790	$ 5,657,837	$ 63,668		$ (447,323)			$ 18,906,887	$ 2,127,532
Profit (loss) for the year	1,401,210					1,707,222						1,707,222	(306,012)
Other comprehensive income (loss) for the year	(236,421)					(36,141)	(200,280)					(236,421)
Total comprehensive income (loss)	1,164,789					1,671,081	(200,280)					1,470,801	(306,012)
Appropriations of prior year's earnings:
Legal reserve (Note 22)					223,047	(223,047)
Cash dividends (Notes 11 and 22)	(1,792,553)					(1,792,553)						(1,792,553)
Share-based payments	(71,913)			56,689								56,689	(128,602)
Restricted shares	262,235		4,347	10,755		14			247,119			262,235
Repurchase of shares (Note 23)	(1,007,654)									$ (1,007,654)		(1,007,654)
Reclassification to equity related to non-current assets held for sale							(287,645)	$ 287,645
Effect of capital reorganization (Note 31)	(3,341,621)		(96,750)	3,065,533		(5,052,343)	434,857					(1,648,703)	$ (1,692,918)
Ending Balance at Dec. 31, 2016	16,247,702		8,869,663	6,888,826	1,137,837	260,989	10,600	287,645	(200,204)	(1,007,654)		$ 16,247,702
Profit (loss) for the year	2,796,882					2,796,882
Other comprehensive income (loss) for the year	(189,902)					42,072	(232,652)							$ 678
Total comprehensive income (loss)	2,606,980					2,838,954	(232,652)							678
Appropriations of prior year's earnings:
Legal reserve (Note 22)					28,680	(28,680)
Cash dividends (Notes 11 and 22)	(257,026)					(257,026)
Cash distribution from capital surplus (Notes 11 and 22)	(599,728)			(599,728)
Restricted shares	123,021		(6,692)	(17,650)		1,729			145,634
Effect of disposal of subsidiary							287,645	$ (287,645)
Ending Balance (Previously stated [member]) at Dec. 31, 2017	18,120,949		8,862,971	6,271,448	1,166,517	2,815,966	65,593		(54,570)	(1,007,654)				678
Ending Balance (Increase (decrease) due to changes in accounting policy required by IFRSs [member]) at Dec. 31, 2017	107,215					65,050								$ (678)	$ 42,843
Ending Balance (Restated balance [member]) at Dec. 31, 2017	18,228,164		8,862,971	6,271,448	1,166,517	2,881,016	65,593		(54,570)	(1,007,654)					42,843
Ending Balance at Dec. 31, 2017	18,120,949
Profit (loss) for the year \| Previously stated [member]	1,301,093
Profit (loss) for the year	1,325,824	$ 43,313				1,325,824
Other comprehensive income (loss) for the year	(32,829)	(1,072)				(45,807)	(51,077)								64,055
Total comprehensive income (loss)	1,292,995	42,241				1,280,017	(51,077)								64,055
Appropriations of prior year's earnings:
Legal reserve (Note 22)					302,653	(302,653)
Cash dividends (Notes 11 and 22)	(256,806)					(256,806)
Restricted shares	41,043		(4,948)	(7,967)		1,089			52,869
Capital reduction	(1,284,223)		(1,329,446)	72						45,151	$ 1,475
Ending Balance at Dec. 31, 2018	$ 18,021,173	$ 588,735	$ 7,528,577	$ 6,263,553	$ 1,469,170	$ 3,602,663	$ 14,516		$ (1,701)	$ (962,503)					$ 106,898

Consolidated Statements of Cash Flows $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)	Dec. 31, 2016 TWD ($)
Cash flows from operating activities
Profit before income tax - continuing operations	$ 1,782,442	$ 58,231	$ 1,532,416	$ 1,700,435
Profit (loss) before income tax - discontinued operations			1,814,953	(122,105)
Profit before income tax including discontinued operations	1,782,442	58,231	3,347,369	1,578,330
Adjustments to reconcile profit before income tax to net cash flows :
Depreciation of property, plant and equipment	3,376,579	110,310	2,899,278	3,228,441
Amortization of assets				2,838
Allowance (reversal) for impairment of accounts and notes receivable			(87)	87
Expected credit losses	348	12
Interest expense	152,416	4,979	192,839	145,151
Interest income	(49,971)	(1,633)	(53,587)	(42,307)
Dividend income	(571)	(19)
Impairment of property, plant and equipment			956	8,198
Gain on valuation of financial assets at fair value through profit or loss	(1,485)	(49)	(637)
Gain on disposal of property, plant and equipment, net	(14,274)	(466)	(132,774)	(6,839)
Gain on disposal of a subsidiary			(1,843,234)
Insurance compensation income	(147)	(5)	(486,858)
Share of (profit) loss of associates	300,101	9,804	179,491	(28,924)
Gain on disposal of long-term investment in associates			(16,929)
Donations				127
Share-based payments	41,043	1,341	123,021	356,463
Deferred revenue	(42,857)	(1,400)	(11,995)	(2,403)
Current contract assets	(44,858)	(1,465)
Accounts and notes receivable	(733,695)	(23,969)	127,800	(480,348)
Accounts receivable - related parties	(129)	(4)	(240)
Other receivables	5,238	171	(15,644)	(124,226)
Other receivables - related parties	16,317	533	35,855
Inventories	(58,101)	(1,898)	(63,910)	(347,133)
Prepayments	46,781	1,528	126,708	12,291
Other financial assets			1,600	17,243
Financial assets at fair value through profit or loss	1,447	47	637
Other non-current assets	6,914	226	6,914	6,914
Current contract liabilities	280	9
Accounts payable	(50,689)	(1,656)	(147,859)	215,555
Accounts payable - related parties	121	4	263
Other payables	(301,711)	(9,857)	438,682	(249,607)
Other payables - related parties	182	6	(43,144)
Current provisions	(27,803)	(908)	46,592	(16,184)
Receipts in advance			(5,913)	2,150
Current refund liabilities	(37,529)	(1,226)
Other current liabilities	(475)	(16)	(15,469)	22,878
Net defined benefit liability, non-current	(17,722)	(579)	(17,604)	(15,886)
Cash generated from operations	4,348,192	142,051	4,672,121	4,282,809
Interest received	48,590	1,587	47,815	44,413
Dividend received	6,184	202	14,325	5,730
Interest paid	(154,307)	(5,041)	(189,381)	(145,668)
Income tax paid	(119,473)	(3,903)	(387,590)	(499,293)
Net cash generated from operating activities	4,129,186	134,896	4,157,290	3,687,991
Cash flows from investing activities
Proceeds from disposal of property, plant and equipment	18,160	593	306,634	59,134
Proceeds from insurance compensation	147	5	486,858
Net cash flow from disposal of a subsidiary			1,781,213
Acquisition of property, plant and equipment	(4,154,198)	(135,714)	(4,682,705)	(4,471,465)
Acquisition of available-for-sale financial assets			(10,940)
Acquisition of investment in associate	(794,694)	(25,962)	(1,373,486)
Decrease (increase) in refundable deposits	(664)	(21)	(11)	407
Increase in other non-current assets				(139,304)
Increase in financial assets at amortized cost	(198,030)	(6,469)
Increase in other financial assets			(964)	(5,466)
Net cash used in investing activities	(5,129,279)	(167,568)	(3,493,401)	(4,556,694)
Proceeds from short-term bank loans	1,053,202	34,407	5,560,354	3,820,594
Payments on short-term bank loans	(2,022,555)	(66,075)	(4,278,518)	(4,969,469)
Proceeds from long-term bank loans	12,663,550	413,706	148,829	10,560,000
Payments on long-term bank loans	(12,553,300)	(410,104)	(1,124,699)	(6,200,567)
Decrease in guarantee deposits	(279)	(9)	(33)	(44)
Payments on repurchase of shares				(1,007,654)
Cash paid in respect of share-based payments				(292,623)
Cash dividend	(256,806)	(8,390)	(257,026)	(1,792,553)
Cash distribution from capital surplus			(599,728)
Payments on capital reduction	(1,284,223)	(41,954)
Payments on capital reorganization				(3,341,621)
Net cash used in financing activities	(2,400,411)	(78,419)	(550,821)	(3,223,937)
Net increase (decrease) in cash and cash equivalents	(3,400,504)	(111,091)	113,068	(4,092,640)
Effect of foreign exchange rate changes	7,312	239	(38,617)	(73,447)
Cash and cash equivalents at beginning of year	8,035,714	262,519	7,961,263	12,127,350
Cash and cash equivalents at end of year	$ 4,642,522	$ 151,667	$ 8,035,714	$ 7,961,263

Corporate and group information

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Corporate and group information

1.	*Corporate and group information*

ChipMOS TECHNOLOGIES INC. (the “Company” or “ChipMOS Taiwan”) was incorporated in the Republic of China (“ROC”) on July 28, 1997. The Company and its subsidiaries (collectively referred herein as the “Group”) are primarily engaged in the research, development, manufacturing and sale of high-integration and high-precision integrated circuits and related assembly and testing services. On April 11, 2014, the Company’s shares were listed on the Taiwan Stock Exchange (“TWSE”). On November 1, 2016, the Company’s American Depositary Shares (“ADSs”) was listed on the NASDAQ Global Select Market and traded under the ticker symbol “IMOS”.

As of October 31, 2016, the former parent company, ChipMOS TECHNOLOGIES (Bermuda) LTD. (“ChipMOS Bermuda”) owned 60.25% of ChipMOS Taiwan’s outstanding shares, was merged with and into ChipMOS Taiwan, with the latter being the surviving company after the merger, pursuant to the agreement and plan of merger, dated January 21, 2016, by and between ChipMOS Bermuda and ChipMOS Taiwan (the “Merger”). Detailed information about the capital reorganization is provided in Note 2 cc).

As of November 30, 2016, the Board of Directors of the Company approved an agreement to form a joint-venture between the Company and Tsinghua Unigroup Ltd. (“Tsinghua Unigroup”). Under the joint-venture agreement, ChipMOS TECHNOLOGIES (BVI) LTD. (“ChipMOS BVI”), a wholly-owned subsidiary of ChipMOS Taiwan, sold 54.98% of the equity interests of its wholly-owned subsidiary, Unimos Microelectronics (Shanghai) Co., Ltd. (“Unimos Shanghai”) formerly known as ChipMOS TECHNOLOGIES (Shanghai) LTD. and renamed in July 2018, to a group led by Tsinghua Unigroup (“strategic investors”). After the consummation of such equity interest transfer, ChipMOS BVI owns 45.02% of the equity interests of Unimos Shanghai. As of December 31, 2016, the assets, liabilities and equity related to Unimos Shanghai have been reclassified as held for sale and presented as discontinued operations for satisfying the definition of discontinued operations. The equity transfer was completed in March 2017. Please see Note 20 for detailed information.

Basis of preparation of financial statements and principal accounting policies

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Basis of preparation of financial statements and principal accounting policies

2.	*Basis of preparation of financial statements and principal accounting policies*

Basis of preparation

These consolidated financial statements have been prepared in accordance with International Financial Reporting Standards (“IFRSs”), which collective term includes all applicable individual IFRSs, International Accounting Standards (“IASs”) issued by the International Accounting Standards Board (“IASB”) and Interpretations issued by the International Financial Reporting Interpretations Committee (“IFRIC”) of the IASB.

The consolidated financial statements have been prepared on a historical cost basis, except for the following items:

(a)

Financial assets at fair value through profit or loss (including derivative instruments).

(b)

Financial assets at fair value through other comprehensive income.

(c)

Defined benefit liabilities were recognized based on the net amount of pension fund assets less the present value of benefit obligation.

These consolidated financial statements are presented in New Taiwan dollars (“NT$”), which is the Company’s functional currency.

New and amended standards adopted by the group


New Standards, Interpretations and Amendments		Effective date issued by IASB
IFRS 9, “Financial Instruments”		January 1, 2018
IFRS 15, “Revenue from Contracts with Customers”		January 1, 2018

(a)

IFRS 9 “Financial Instruments”

(i)

Debt instruments are classified as financial assets measured at the fair value through profit or loss, financial assets measured at fair value through other comprehensive income or financial assets measured at amortized cost according to the characteristics of the entity’s business model and the contractual cash flows. Equity instruments are classified as financial assets measured at the fair value through profit or loss, unless an entity irrevocably designates an investment in equity instruments that is not held for trading as measured at fair value through other comprehensive income.

(ii)

The expected loss model is used to assess the impairment losses of debt instruments. The 12 months expected credit loss or lifetime expected credit loss is adopted if the credit risk of a financial instrument has increased significantly since the initial recognition at each statement of financial position date. Unless the instrument has been impaired, the interest income is calculated on the gross carrying amount of the asset; if the instrument has been impaired, the interest income after the impairment is calculated based on the book value (net of allowance) of the asset. The Group shall always measure the loss allowance at an amount equal to lifetime expected credit losses for trade receivables that do not contain a significant financing component.

(iii)

IFRS 9 “Financial Instruments” (“IFRS 9”) replaces the provisions of IAS 39 “Financial Investments” (“IAS 39”) that relate to the recognition, classification and measurement of financial assets and financial liabilities, derecognition of financial instruments, impairment of financial assets and hedge accounting. The new accounting policies are set out in Note 2 j). In accordance with the transitional provisions in IFRS 9, comparative figures have not been restated with the exception of certain aspects of hedge accounting.

(iv)

The application of IFRS 9 from January 1, 2018 resulted in changes in accounting policies and adjustments to the amounts recognized in the financial statements. Please refer to Note 41 for the details of significant effects as of January 1, 2018 on applying the aforementioned new standard.

(b)

IFRS 15 “Revenue from Contracts with Customers” and amendments

(i)

IFRS 15 “Revenue from Contracts with Customers” (“IFRS 15”) replaces IAS 11 “Construction Contracts”, IAS 18 “Revenue” and relevant interpretations. According to IFRS 15, revenue is recognized when a customer obtains control of promised goods or services. A customer obtains control of goods or services when a customer has the ability to direct the use of, and obtain substantially all of the remaining benefits from, the asset.

(ii)

The core principle of IFRS 15 is that an entity recognizes revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. An entity recognizes revenue in accordance with that core principle by applying the following five steps:

Step

1: Identify the contract(s) with a customer.

Step

2: Identify the performance obligations in the contract(s).

Step

3: Determine the transaction price.

Step

4: Allocate the transaction price to the performance obligations in the contract(s).

Step

5: Recognize revenue when (or as) the entity satisfies the performance obligation.

Furthermore, IFRS 15 includes a set of comprehensive disclosure requirements that requires an entity to disclose sufficient information to enable users of financial statements to understand the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers.

(iii)

When applying IFRS 15 effective from January 1, 2018, the Group intends not to restate the financial statements of prior period, the cumulative impact of the application was recognized as retained earnings as of January 1, 2018. The Group applied IFRS 15 only to incomplete contracts as of January 1, 2018. The new accounting policies are set out in Note 2 s). Please refer to Note 42 for the details of significant effects as of January 1, 2018 on applying the aforementioned new standard.

New and revised International Financial Reporting Standards not yet adopted

Amendments to IFRSs which have been published but are not mandatory for the financial year ending December 31, 2018 are not expected to have a material impact on the Group. Major Amendment to IFRSs that are not yet effective are listed below:


New Standards, Interpretations and Amendments		Effective date issued by IASB
IFRS 16, “Leases”		January 1, 2019

IFRS 16, “Leases”, supersedes IAS 17, “Leases” and related interpretations. The standard requires lessees to recognize a right-of-use asset and a lease liability (except for those leases with terms of 12 months or less and leases of low-value assets). The accounting treatment is the same for lessors, who classify their leases as either finance leases or operating leases and account for those two types of leases differently. IFRS 16 only requires enhanced disclosures to be provided by lessors.

The Group has reported its preliminary assessment to the Board of Directors in the fourth quarter of 2018 and determined IFRS 16 will have significant impact on the Group’s financial position. The Group intends to apply the simplified transition approach and will not restate comparative amounts for the years prior to first adoption.

In applying IFRS 16 for the first time, the Group has used the following practical expedients permitted by the standard:

•

the use of a single discount rate to a portfolio of leases with reasonably similar characteristics,

•

the accounting for operating leases with a remaining lease term of less than 12 months as of January 1, 2019 as short-term leases,

•

the use of hindsight in determining the lease term where the contract contains options to extend or terminate the lease.

At the date of January 1, 2019, the Group considers to adopt the modified retrospective transitional provisions of IFRS 16, and expected to increase right-of-use asset and lease liabilities by NT$898,387 thousand (US$29,349 thousand) and NT$884,275 thousand (US$28,888 thousand), respectively; and decrease lease asset by NT$31,904 thousand (US$1,042 thousand) and lease obligations payable NT$17,792 thousand (US$581 thousand).

Other Amendments to IFRSs not listed above are not expected to have a material impact on the entity in the current or future reporting periods and on foreseeable future transactions.

Basis of consolidation

The consolidated financial statements include the accounts of ChipMOS Taiwan and all entities controlled by ChipMOS Taiwan. The financial statements of subsidiaries are prepared for the same reporting period as the Company, using consistent accounting policies. The results of subsidiaries are consolidated from the date on which the Group obtains control, and continue to be consolidated until the date that such control ceases.

Profit or loss and each component of other comprehensive income are attributed to the owners of the parent and to the non-controlling interests, even if this results in the non-controlling interests having a deficit balance. All intra-group transactions, balances, income and expenses are eliminated in full on consolidation.

The Group reassesses whether or not it controls an investee if facts and circumstances indicate that there are changes to one or more of the three elements of control described in the accounting policy for subsidiaries below.

Changes in the Group’s ownership interests in subsidiaries that do not result in the Group losing control over the subsidiaries are accounted for as equity transactions. The carrying amounts of the Group’s interests and the non-controlling interests are adjusted to reflect the changes in their relative interests in the subsidiaries. Any difference between the amount by which the non-controlling interests are adjusted and the fair value of the consideration paid or received is recognized directly in equity and attributed to owners of the Company.

When the Group loses control of a subsidiary, the profit or loss on disposal is calculated as the difference between (i) the aggregate of the fair value of the consideration received and the fair value of any investment retained and (ii) the previous carrying amount of the assets (including goodwill), and liabilities of the subsidiary and any non-controlling interests. The Group’s share of components previously recognized in other comprehensive income is reclassified to consolidated statements of comprehensive income or retained profits, as appropriate, on the same basis as would be required if the Group had directly disposed of the related assets or liabilities.

Subsidiaries included in the consolidated financial statements:

Percentage of
Ownership (%)

December 31,

Name of investor

Name of investee

Main businesses

Location

2017

2018

The Company

ChipMOS U.S.A., Inc. (“ChipMOS USA”)

Research, development and marketing of semiconductors, circuits, and electronic related products

San Jose, USA

100

The Company

ChipMOS BVI

Holding company

British Virgin Islands

100

Significant judgments and estimates

The preparation of consolidated financial statements requires management to make judgments, estimates and assumptions that affect the recorded amounts of assets, liabilities, revenue and expenses of the Group. The Group continually evaluates these estimates, including those related to share-based payments, impairment of receivables, impairment of non-financial assets, depreciation of property, plant and equipment, defined benefit plans, deferred tax assets and deferred tax liabilities. The Group bases its estimates on historical experience and other assumptions, which it believes to be reasonable under the circumstances. Actual results may differ from these estimates under different assumptions and conditions.

The estimates and underlying assumptions are reviewed on an ongoing basis. Revisions to accounting estimates are recognized in the period in which the estimate is revised if the revision affects only that periods, or in the period of the revision and future periods if the revision affects both current and future periods.

Management has considered the development, selection and disclosure of the Group’s critical accounting policies and estimates.

Judgments

In the process of applying the Group’s accounting policies, management has made the following judgments which have the most significant effect on the amounts recognized in the consolidated financial statements:

Provisions for deficiency compensation

The Group is primarily providing high-integration and high-precision integrated circuit of the packaging and testing services. In cases of deficiencies in the assembly and testing services provided, the Group has to clarify the reason for deficiencies and attribution of responsibility. The Group follows the guidance of IAS 37 “Provisions, Contingent Liabilities and Contingent Assets” to determine provisions for deficiency compensation. Since the timing and amount of these provisions are based on assumptions and estimates it requires management to make critical judgments.

Estimates and assumptions

Revenue recognition

The Group recognizes revenue from services for assembly, LCDD and Bumping based on the progress towards completion of performance obligation during the service period. The Group estimates total expected input costs based on historical experience and measures the progress towards completion by the actual input costs relative to the total expected input costs.

Refund liabilities

The Group estimates sales refund liabilities for sales allowance based on historical results and other known factors. Provisions for such liabilities are recorded as a deduction to revenues when the sales are recognized. The Group reassesses the reasonableness of estimates of discounts and returns periodically.

Causes and effects of accounting change

By considering the Group’s experience on using similar property, plant and equipment in prior periods as well as by referring to the experience from peer industry, on November 10, 2016, the Board of Directors approved to change the estimated useful lives of certain properties from 11 years to 16 years and certain equipment from 2~6 years to 2~8 years effectively from November 1, 2016, in order to better reflect economic benefits from usage of those properties and equipment. The impact on depreciation expenses of current and future periods were expected as follows:


	2016			2017			2018			2019
	NT$000			NT$000			NT$000			NT$000
Decrease in depreciation expenses		(119,737	)		(605,259	)		(391,669	)		(164,863	)

Property, plant and equipment and depreciation

Property, plant and equipment are stated at cost, less provision for depreciation and impairment losses, if any.

The cost of an item of property, plant and equipment comprises its purchase price and any directly attributable cost of bringing the asset to its working condition and location for its intended use. Expenditure incurred after the item has been put into operation, such as repairs and maintenance and overhaul costs, is normally charged to the consolidated statements of comprehensive income in the year in which it is incurred. In situations where it can be clearly demonstrated that the expenditure has resulted in an increase in future economic benefits expected to be obtained from the use of the item, the expenditure is capitalized as an additional cost of the item. When an item of property, plant and

equipment is disposed of or retired, its cost and accumulated depreciation are removed from the financial statements and any gain or loss resulting from the disposal or retirement, being the difference between the net proceeds and the carrying amount of the asset, is included in consolidated statements of comprehensive income.

Depreciation is provided on the straight-line method, based on the estimated useful life of the individual assets, as follows:


Buildings		5 to 51 years
Machinery and equipment		2 to 8 years
Tools		2 to 4 years
Other equipment		2 to 6 years

Where parts of an item of property, plant and equipment have different useful lives, the cost of that item is allocated on a reasonable basis among the parts and each part is depreciated separately. Residual values, useful lives and the depreciation method are reviewed, and adjusted if appropriate, at least at each financial year end.

An item of property, plant and equipment including any significant part initially recognized is derecognized upon disposal or when no future economic benefits are expected from its use or disposal. Any gain or loss on disposal or retirement recognized in the consolidated statements of comprehensive income in the year the asset is derecognized is the difference between the net sales proceeds and the carrying amount of the relevant asset.

Impairment of non-financial assets

Where an indication of impairment exists, or when periodical impairment testing for an asset is required (other than inventories, deferred tax assets and financial assets), the recoverable amount of the asset is estimated. An asset’s recoverable amount is the higher of the value in use of the asset or cash-generating unit to which it belongs and its fair value less costs to sell, and is determined for an individual asset, unless the asset does not generate cash inflows that are largely independent of those from other assets or groups of assets, in which case the recoverable amount is determined for the cash-generating unit to which the asset belongs.

An impairment loss is recognized only if the carrying amount of an asset exceeds its recoverable amount. In assessing value in use, the estimated future cash flows are discounted to their present value using a pre-tax discount rate that reflects current market assessments of the time value of money and the risks specific to the asset. An impairment loss is charged to the consolidated statements of comprehensive income in the period in which it arises in those expense categories consistent with the function of the impaired asset.

An assessment is made at the end of each reporting period as to whether there is any indication that previously recognized impairment losses may no longer exist or may have decreased. If such indication exists, the recoverable amount is estimated. A previously recognized impairment loss of an asset is reversed only if there has been a change in the estimates used to determine the recoverable amount of that asset, but not to an amount higher than the carrying amount that would have been determined (net of any depreciation), had no impairment loss been recognized for the asset in prior years. A reversal of such impairment loss is credited to the consolidated statements of comprehensive income in the period in which it arises.

Inventories

Inventories are stated at the lower of cost and net realizable value. Cost is determined on a weighted average cost basis and includes all costs of purchase, costs of conversion, and other costs incurred in bringing the inventories to their present location and condition.

Net realizable value is the estimated selling price in the ordinary course of business less the estimated costs of completion and the estimated costs necessary to make the sale.

When inventories are consumed, the carrying amount of those inventories is recognized as cost of revenue in the period in which the related revenue is recognized. The amount of any write-down of inventories to net realizable value and all losses of inventories are recognized as cost of revenue in the period the write-down or loss occurs. The amount of any reversal of any write-down of inventories is recognized as a reduction in the amount of inventories recognized as cost of revenue in the period in which the reversal occurs.

Non-current assets held for sale

Non-current assets are classified as assets held for sale when their carrying amount is to be recovered principally through a sale transaction rather than through continuing use, and a sale is considered highly probable. They are stated at the lower of carrying amount and fair value less costs to sell.

Investments and other financial assets

Classification

From 1 January, 2018, the group classifies its financial assets in the following measurement categories:

(a)

those to be measured subsequently at fair value (either through other comprehensive income (“OCI”) or through profit or loss), and

(b)

those to be measured at amortized cost.

The classification depends on the entity’s business model for managing the financial assets and the contractual terms of the cash flows.

For assets measured at fair value, gains and losses will either be recorded in profit or loss or OCI. For investments in equity instruments that are not held for trading, this will depend on whether the group has made an irrevocable election at the time of initial recognition to account for the equity investment at fair value through other comprehensive income (“FVTOCI”).

Recognition and derecognition

Regular way purchases or sales of financial assets are recognized on settlement date, the date on which the group complete the purchase or sell the asset. Financial assets are derecognized when the rights to receive cash flows from the financial assets have expired or have been transferred and the group has transferred substantially all the risks and rewards of ownership.

Measurement

At initial recognition, the group measures a financial asset at its fair value plus, in the case of a financial asset not at fair value through profit or loss (“FVTPL”), transaction costs that are directly attributable to the acquisition of the financial asset. Transaction costs of financial assets carried at FVTPL are expensed in profit or loss.

Debt instruments

Subsequent measurement of debt instruments depends on the group’s business model for managing the asset and the cash flow characteristics of the asset. There are three measurement categories into which the group classifies its debt instruments:

Amortized cost: Assets that are held for collection of contractual cash flows where those cash flows represent solely payments of principal and interest are measured at amortized cost. Interest income from these financial assets is included in finance income using the effective interest rate method. Any gain or loss arising on derecognition is recognized directly in profit or loss.

FVTPL: Assets that do not meet the criteria for amortized cost or FVTOCI are measured at FVTPL. A gain or loss on a debt investment that is subsequently measured at FVTPL is recognized in profit or loss.

Equity instruments

The group subsequently measures all equity investments at fair value. Where the group’s management has elected to present fair value gains and losses on equity investments in OCI, there is no subsequent reclassification of fair value gains and losses to profit or loss following the derecognition of the investment. Dividends from such investments continue to be recognized in profit or loss as other income when the group’s right to receive payments is established.

Changes in the fair value of financial assets at FVTPL are recognized in other non-operating income (expenses) in the statement of comprehensive income as applicable. Impairment losses (and reversal of impairment losses) on equity investments measured at FVTOCI are not reported separately from other changes in fair value.

Impairment

For financial assets at amortized cost, at each reporting date, the Group recognizes the impairment provision for 12 months expected credit losses if there has not been a significant increase in credit risk since initial recognition or recognizes the impairment provision for the lifetime expected credit losses if such credit risk has increased since initial recognition after taking into consideration all reasonable and verifiable information that includes forecasts. On the other hand, for accounts receivable or contract assets that do not contain a significant financing component, the Group recognizes the impairment provision for lifetime expected credit losses.

Investments in associates

The Group’s investments in associates are accounted for using the equity method. An associate is an entity over which the Group has significant influence and that is neither a subsidiary nor a joint venture. Significant influence is the power to participate in the financial and operating policy decisions of an entity, but is not control or joint control over those policies. Any difference between the acquisition cost and the Group’s share of the net fair value of the identifiable assets and liabilities of associates is accounted for as follows:

(a)

Any excess of the acquisition cost over the Group’s share of the net fair value of the identifiable assets and liabilities of an associate at the date of acquisition is recognized as goodwill and is included in the carrying amount of the investment. Amortization of goodwill is not permitted.

(b)

Any excess of the Group’s share of the net fair value of the identifiable assets and liabilities of an associate over the acquisition cost, after reassessing the fair value, is recognized as a gain in profit or loss on the acquisition date.

Under the equity method, the investments in associates are carried on the statements of financial position at cost plus post acquisition changes in the Group’s share of profit or loss and other comprehensive income of associates. The Group’s share of changes in associates’ profit or loss and other comprehensive income are recognized directly in profit or loss and other comprehensive income, respectively, of the Group. Distributions received from an associate reduce the carrying amount of the investment. Any unrealized gains and losses resulting from transactions between the Group and the associate are eliminated to the extent of the Group’s interest in the associate.

Upon an associate’s issuance of new shares, if the Group takes up more shares than its original proportionate holding while maintaining its significant influence over that associate, such increase would be accounted for as an acquisition of an additional equity interest in the associate. Upon an associate’s issuance of new shares, if the Group does not take up proportionate shares and reduces its shareholding while maintaining its significant influence over that associate, the Group will treat the transaction as deemed disposal and reclassify to profit or loss the proportion of the gain or loss previously recognized in other comprehensive income relating to that reduction in ownership interest where appropriate.

The Group ceases to use the equity method upon loss of significant influence over an associate. Any difference between the carrying amount of the investment in an associate upon loss of significant influence and the fair value of the retained investment plus proceeds from disposal will be recognized in profit or loss.

The Group determines at each reporting date whether there is any objective evidence that the investments in associates are impaired. An impairment loss, being the difference between the recoverable amount of the associate and its carrying value, is recognized in profit or loss in the consolidated statements of comprehensive income and forms part of the carrying amount of the investments.

Financial liabilities

Initial recognition and measurement

Financial liabilities are classified, at initial recognition, as financial liabilities at fair value through profit or loss, loans and borrowings, or as derivatives designated as hedging instruments in an effective hedge, as appropriate.

All financial liabilities are recognized initially at fair value and, in the case of loans and borrowings, net of directly attributable transaction costs.

The Group’s financial liabilities include bank loans, accounts payable and other monetary liabilities.

Subsequent measurement

The subsequent measurement of financial liabilities depends on their classification as follows:

Loans and borrowings

After initial recognition, interest-bearing loans and borrowings are subsequently measured at amortized cost, using the effective interest rate method unless the effect of discounting would be immaterial, in which case they are stated at cost. Gains and losses are recognized in the consolidated statements of comprehensive income when the liabilities are derecognized through the effective interest rate amortization process.

Amortized cost is calculated by taking into account any discount or premium on acquisition and fees or costs that are an integral part of the effective interest rate. The effective interest rate amortization is included in finance costs in the consolidated statements of comprehensive income.

Notes and accounts payable

Notes and accounts payable are obligations to pay for raw materials, goods or services that have been acquired in the ordinary course of business from suppliers. They are recognized initially at fair value and subsequently measured at amortized cost using the effective interest method. However, short-term accounts payable without bearing interest are subsequently measured at initial invoice amount as the effect of discounting is immaterial.

Derecognition of financial liabilities

A financial liability is derecognized when the obligation under the liability is discharged or cancelled, or expired. When an existing financial liability is replaced by another from the same lender on substantially different terms, or the terms of an existing liability are substantially modified, such an exchange or modification is treated as a derecognition of the original liability and a recognition of a new liability, and the difference between the respective carrying amounts is recognized in the consolidated statements of comprehensive income.

Dividends

Dividends are recommended by the Board of Directors to the Shareholders’ approval pursuant to the Company’s Article of Incorporation.

Operating lease charges

Where the Group has the use of assets held under operating leases, payments made under the leases are charged to the consolidated statements of comprehensive income in equal installments over the accounting periods covered by the lease term, except where an alternative basis is more representative of the pattern of benefits to be derived from the leased assets. Lease incentives received are recognized in the consolidated statements of comprehensive income as an integral part of the aggregate net lease payments made. Contingent rentals, if any, are charged to the consolidated statements of comprehensive income in the accounting period in which they are incurred.

Treasury stock

Treasury stock is stated at cost and shown as a deduction in equity. When the Company retires treasury stock, the treasury stock account is reduced and the share capital as well as the capital surplus – share premium are reversed on a pro rata basis. When the book value of the treasury stock exceeds the sum of par value and share premium, the difference is charged to respective capital surplus and to retained earnings for any remaining amount.

Provisions for deficiency compensation

A provision is recognized when a present obligation (legal or constructive) has arisen as a result of a past event and it is probable that a future outflow of resources will be required to settle the obligation, provided that a reliable estimate can be made of the amount of the obligation.

When the effect of discounting is material, the amount recognized for a provision is the present value at the end of the reporting period of the future expenditures expected to be required to settle the obligation. The increase in the discounted present value amount arising from the passage of time is included in finance costs in the consolidated statements of comprehensive income.

Foreign currency translation

The consolidated financial statements are presented in New Taiwan dollars, which is the Company’s functional currency. Each entity in the Group determines its own functional currency and items included in the financial statements of each entity are measured using that functional currency. Foreign currency transactions are initially recorded using the functional currency rates ruling at the date of the transactions. Monetary assets and liabilities denominated in foreign currencies are retranslated at the functional currency rates of exchange ruling at the end of the reporting period. All differences are taken to profit or loss. Non-monetary items that are measured in terms of historical cost in a foreign currency are translated using the exchange rates at the dates of the initial transactions. Non-monetary items measured at fair value in a foreign currency are translated using the exchange rates at the date when the fair value was determined. The functional currencies of certain overseas subsidiaries are currencies other than the New Taiwan dollars. As at the end of the reporting period, the assets and liabilities of these entities are translated into the presentation currency of the Company at the exchange rates ruling at the end of the reporting period, and their income and expense items are translated into New Taiwan dollars at the weighted average exchange rates for the year.

The resulting exchange differences are recorded in other comprehensive income and the cumulative balance is included in foreign currency translation reserve in the consolidated statements of changes in equity. On disposal of a foreign entity, the deferred cumulative amount recognized in foreign currency translation reserve relating to that particular foreign operation is recognized in the consolidated statements of comprehensive income. For the purpose of the consolidated statements of cash flows, the cash flows of overseas subsidiaries are translated into New Taiwan dollars at the exchange rates ruling at the dates of the cash flows. Frequently recurring cash flows of overseas subsidiaries which arise throughout the year are translated into New Taiwan dollars at the weighted average exchange rates for the year.

Revenue recognition

The Group is primarily engaged in the customized assembly and testing services of high-integration and high-precision integrated circuits based on customer’s specification demand to create or enhance the product. When providing assembly and testing services, the Group considers:

(a)

Customer controls the provided raw materials and the Group receives the instruction from the customer on providing assembly and testing services and subsequent treatments.

(b)

The Group provides assembly and testing services to create or enhance an asset which solely provided and controlled by the customer. The Group has no right to transfer the asset for another use.

As the asset ownership belongs to the customer, who bears the significant risk and rewards and rights on the use of the asset, the Group recognizes assembly and testing service revenue over time based on the progress towards completion during the service period.

The progress towards completion on assembly services, services for Liquid Crystal Display and other Flat-Panel Display Driver Semiconductors (“LCDD”) and Bumping are measured by the actual input costs relative to estimate total expected input costs. The progress towards completion on testing services is measured by the actual incurred testing volume comparing to planned total testing volume. The Group believes that aforementioned methods are the most appropriate manner to measure the satisfaction of performance obligation to customers because the input costs incurred to assembly and testing volume complete in testing services are based on customer’s specification and not linear over the duration of these services. Customer payment on assembly and testing services is based on predetermined payment schedule. A contract asset is recognized when the Group provides services in excess of customer’s payment. A contract liability is recognized upon receipt of prepayment from a customer for its performance obligation to transfer services in the future.

Interest income

Interest income is recognized on an accrual basis using the effective interest method by applying the rate that discounts the estimated future cash receipts through the expected life of the financial instrument to the net carrying amount of the financial asset.

Research and development costs

Research and development costs that do not meet the criteria of internally generated intangible assets of IAS 38 “Intangible Assets” are expensed in the period in which it is incurred.

Borrowing costs

Borrowing costs directly attributable to the acquisition, construction or production of qualifying assets, which are assets that necessarily take a substantial period of time to get ready for their intended use or sale, are added to the cost of those assets, until such time as the assets are substantially ready for their intended use or sale. All other borrowing costs are charged to the consolidated statements of comprehensive income in the period in which they are incurred.

Pension and other post-employment benefits

The Group operates defined contribution and defined benefit plans in the ROC. For defined contribution retirement benefit plans, payments to the benefit plan are recognized as an expense when the employees have rendered service entitling them to the contribution. For defined benefit retirement plans, the cost of providing benefit is recognized based on actuarial calculations.

For defined benefit retirement benefit plans, the cost of providing benefits is determined using the Projected Unit Credit Method, with actuarial valuations being carried out at the year end. Remeasurements are recognized in other comprehensive income in the period which they incur. Past service costs are recognized in the consolidated statements of comprehensive income on the earlier of the date of the plan amendment or curtailment, and the date that the Group recognizes restructuring-related costs. Net interest is calculated by applying the discount rate to the net defined benefit liability or asset. The Group recognizes i) service costs comprising current service costs, past service costs, gains and losses on curtailments and non-routine settlements, and ii) net interest expense or income, under cost of revenue, research and development expenses, sales and marketing expenses and general and administrative expenses in the consolidated statements of comprehensive income.

Employee entitlements to annual leave are recognized when they accrue to employees. An accrual is made for the estimated liability for annual leave as a result of services rendered by employees up to the end of the reporting period.

Share-based payments

Restricted shares

Restricted shares issued to employees are measured at the fair value of the equity instruments granted at the grant date, and are recognized as compensation cost over the vesting period.

For restricted shares where those shares do not restrict distribution of dividends to employees and employees are not required to return the dividends received if they resign during the vesting period, the Group recognizes the fair value of the dividends received by the employees who are expected to resign during the vesting period as compensation cost at the date of dividends declared.

For restricted shares where employees do not need to pay to acquire those shares, if the employees who resign during the vesting period, the Group will recover and retire those shares at no cost.

Income tax

Income tax represents the sum of current and deferred tax. Income tax relating to items recognized outside profit or loss is recognized outside profit or loss, either in other comprehensive income or directly in equity.

Current tax assets and liabilities are measured at the amount expected to be recovered from or paid to the taxation authorities, based on tax rates (and tax laws) that have been enacted or substantively enacted by the end of the reporting period, taking into consideration interpretations and practices prevailing in the countries in which the Group operates.

Deferred tax is provided, using the liability method, on all temporary differences at the end of the reporting period between the tax bases of assets and liabilities and their carrying amounts for financial reporting purposes.

Deferred tax liabilities are recognized for all taxable temporary differences, except:

•

when the deferred tax liability arises from the initial recognition of goodwill or an asset or liability in a transaction that is not a business combination and, at the time of the transaction, affects neither the accounting profit nor taxable profit or loss; and

•

in respect of taxable temporary differences associated with investments in subsidiaries, associates and joint ventures, when the timing of the reversal of the temporary differences can be controlled and it is probable that the temporary differences will not reverse in the foreseeable future.

Deferred tax assets are recognized for all deductible temporary differences, the carryforward of unused tax credits and any unused tax losses. Deferred tax assets are recognized to the extent that it is probable that taxable profits will be available against which deductible temporary differences, the carryforward of unused tax credits and unused tax losses can be utilized, except:

•

when the deferred tax asset relating to the deductible temporary differences arises from the initial recognition of an asset or liability in a transaction that is not a business combination and, at the time of the transaction, affects neither the accounting profit nor taxable profit or loss; and

•

in respect of deductible temporary differences associated with investments in subsidiaries, associates and joint ventures, deferred tax assets are only recognized to the extent that it is probable that the temporary differences will reverse in the foreseeable future and taxable profit will be available against which the temporary differences can be utilized.

The carrying amount of deferred tax assets is reviewed at the end of each reporting period and reduced to the extent that it is no longer probable that sufficient taxable profit will be available to allow all or part of the deferred tax asset to be utilized. Unrecognized deferred tax assets are reassessed at the end of each reporting period and are recognized to the extent that it has become probable that sufficient taxable profit will be available to allow all or part of the deferred tax asset to be recovered.

Deferred tax is calculated, without discounting, at the tax rates that are expected to apply in the period when the asset is realized or the liability is settled, based on the tax rates (and tax laws) that have been enacted or substantively enacted by the end of the reporting period.

Current income tax assets and liabilities are offset and the net amount reported in the statements of financial position when there is a legally enforceable right to offset the recognized amounts and there is an intention to settle on a net basis or realize the asset and settle the liability simultaneously.

If a change in tax rate is enacted or substantively enacted, the Group recognizes the effect of the change immediately in the period in which the change occurs. The effect of the change on items recognized outside profit or loss is recognized in other comprehensive income or equity while the effect of the change on items recognized in profit or loss is recognized in profit or loss.

Cash and cash equivalents

Cash and cash equivalents comprise cash on hand and demand deposits, and short-term highly liquid investments which are readily convertible into known amounts of cash, are subject to an insignificant risk of changes in value, and have a short maturity of generally within 3 months when acquired.

Related parties

(a)

A person, or a close member of that person’s family, is related to the Group if that person:

(i)

has control or joint control over the Group;

(ii)

has significant influence over the Group; or

(iii)

is a member of key management personnel of the Group or the Group’s parent.

(b)

An entity is related to the Group if any of the following conditions applies:

(i)

The entity and the Group are members of the same group.

(ii)

One entity is an associate or joint venture of the other entity (or an associate or joint venture of a member of a group of which the other entity is a member).

(iii)

The entity and the Group are joint ventures of the same third party.

(iv)

One entity is a joint venture of a third entity and the other entity is an associate of the third entity.

(v)

The entity is a post-employment benefit plan for the benefit of employees of either the Group or an entity related to the Group.

(vi)

The entity is controlled or jointly controlled by a person identified in (a).

(vii)

A person identified in (a)(i) has significant influence over the entity or is a member of the key management personnel of the entity (or of a parent of the entity).

aa)

Subsidiaries

A subsidiary is an entity (including a structured entity) controlled by the Company. Control is achieved when the Group is exposed, or has rights, to variable returns from its involvement with the investee and has the ability to affect those returns through its power over the investee (i.e., existing rights that give the Group the current ability to direct the relevant activities of the investee).

When the Company has, directly or indirectly, less than a majority of the voting or similar rights of an investee, the Group considers all relevant facts and circumstances in assessing whether it has power over an investee, including:

•

the contractual arrangement with the other vote holders of the investee;

•

rights arising from other contractual arrangements; and

•

the Group’s voting rights and potential voting rights

The Company’s share of its subsidiaries’ post-acquisition profits or losses is recognized in profit or loss, and its share of post-acquisition movements in other comprehensive income is recognized in other comprehensive income. When the Company’s share of losses in a subsidiary equals or exceeds its interest in the subsidiary, the Company continues to recognize its share in the subsidiary’s loss proportionately.

Changes in a parent’s ownership interest in a subsidiary that do not result in the parent losing control of the subsidiary (transactions with non-controlling interests) are accounted for as equity transactions, i.e. transactions with owners in their capacity as owner. Any difference between the amount by which the non-controllinginterests are adjusted and the fair value of the consideration paid or received is recognized directly in equity.

bb)

Fair value measurement

The Group measures its accrued pension cost at fair value at the end of each reporting period. Fair value is the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The fair value measurement is based on the presumption that the transaction to sell the asset or transfer the liability takes place either in the principal market for the asset or liability, or in the absence of a principal market, in the most advantageous market for the asset or liability. The principal or the most advantageous market must be accessible by the Group. The fair value of an asset or a liability is measured using the assumptions that market participants would use when pricing the asset or liability, assuming that market participants act in their economic best interest.

A fair value measurement of a non-financial asset takes into account a market participant’s ability to generate economic benefits by using the asset in its highest and best use or by selling it to another market participant that would use the asset in its highest and best use.

The Group uses valuation techniques that are appropriate in the circumstances and for which sufficient data are available to measure fair value, maximizing the use of relevant observable inputs and minimizing the use of unobservable inputs.

All assets and liabilities for which fair value is measured or disclosed in the financial statements are categorized within the fair value hierarchy, described as follows, based on the lowest level input that is significant to the fair value measurement as a whole:

Level 1: Quoted prices (unadjusted) in active markets for identical assets or liabilities that can be accessed at the measurement date. An active market is a market in which trading for the asset or liability take place with sufficient frequency and volume to provide pricing information on an ongoing basis.

Level 2: Inputs other than quoted prices from Level 1 that are observable information for the asset or liability, either directly or indirectly.

Level 3: Unobservable inputs for the asset or liability. The fair value of the Group’s financial instruments without active market is included in Level 3.

For assets and liabilities that are recognized in the financial statements on a recurring basis, the Group determines whether transfers have occurred between levels in the hierarchy by reassessing categorization (based on the lowest level input that is significant to the fair value measurement as a whole) at the end of each reporting period.

cc)

Capital reorganization

The Company merged with ChipMOS Bermuda on October 31, 2016 and the transaction was accounted as capital reorganization within the Group. When presenting comparative financial statements, the Company presented it as if ChipMOS Bermuda had always been combined and the financial statements were restated retrospectively. The assets and liabilities acquired from ChipMOS Bermuda was measured by using book value method, and any differences between the consideration given by the Company and the aggregate book value of the assets and liabilities of ChipMOS Bermuda was first accounted for as addition (deduction) in capital surplus arises from share premium, if the share premium is insufficient, the amount will be accounted for as deduction from retained earnings. In addition, on the effective date of the Merger, the Company reclassified its shares originally held by ChipMOS Bermuda as treasury stock and cancelled those shares with deduction in share premium equal to the proportion of retired shares. If the share premium is insufficient, the amount will be accounted for as deduction from retained earnings. Transaction costs attributable to the Merger are accounted for as deduction from equity.

When presenting comparative financial statements, the Company presented it as if ChipMOS Bermuda had always been combined and the financial statements were restated retrospectively. Net income attributable to ChipMOS Bermuda prior to the Merger were presented as “Predecessors’ interests”.

Segment Information

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Segment Information

4.	*Segment Information*

The Group engages mainly in the assembly and testing of semiconductors, memory module and investing. In accordance with IFRS 8 “Operating Segments”, the Group’s chief operating decision maker has been identified as the Chairman of the Board of Directors, who reviews these segment results by Testing, Assembly, Testing and Assembly for Liquid Crystal Display and other Flat-Panel Display Driver Semiconductors (“LCDD”) and Bumping when making decisions about allocating resources and assessing the performance of the Group. The information of the segments’ other assets and liabilities are not regularly provided to the Chairman of the Board of Directors for decision making. Financial segment information is as below:


	2016
	Testing			Assembly			LCDD			Bumping			Others			Elimination			Total continuing operations			Discontinued operations
	NT$000			NT$000			NT$000			NT$000			NT$000			NT$000			NT$000			NT$000
Revenue
External customers		4,587,054			5,880,780			4,920,302			2,999,457			—			—			18,387,593			1,005,166
Inter-segment		—			1,103			—			510			41,670			(43,283	)		—			—

Total revenue		4,587,054			5,881,883			4,920,302			2,999,967			41,670			(43,283	)		18,387,593			1,005,166

Operating profit (loss)		1,346,874			143,220			963,698			(341,356	)		(82,331	)		(31,530	)		1,998,575			(146,263	)
Depreciation expenses		(664,026	)		(635,481	)		(1,167,908	)		(622,412	)		(565	)		488			(3,089,904	)		(141,375	)
Interest income		—			—			—			—			51,756			(13,202	)		38,554			3,753
Interest expense		—			—			—			—			(144,545	)		—			(144,545	)		(606	)
Share of profit (loss) of associates		—			—			—			—			(128,866	)		157,790			28,924			—
Purchase of property, plant and equipment		771,500			554,162			910,457			887,144			49			—			3,123,312			1,567,683


	2017
	Testing			Assembly			LCDD			Bumping			Others			Elimination			Total continuing operations			Discontinued operations
	NT$000			NT$000			NT$000			NT$000			NT$000			NT$000			NT$000			NT$000
Revenue
External customers		4,838,246			5,259,281			4,789,869			3,053,459			—			—			17,940,855			227,095
Inter-segment		—			—			247			—			35,808			(36,055	)		—			—

Total revenue		4,838,246			5,259,281			4,790,116			3,053,459			35,808			(36,055	)		17,940,855			227,095

Operating profit (loss)		1,448,939			(55,198	)		1,285,495			(336,123	)		(100,545	)		(2,687	)		2,239,881			(25,394	)
Depreciation expenses		(673,393	)		(597,500	)		(1,048,587	)		(579,605	)		(503	)		310			(2,899,278	)		—
Interest income		—			—			—			—			53,123			—			53,123			464
Interest expense		—			—			—			—			(190,425	)		—			(190,425	)		(2,414	)
Share of profit (loss) of associates		—			—			—			—			1,347,851			(1,527,342	)		(179,491	)		—
Purchase of property, plant and equipment		836,894			655,879			2,615,153			594,765			—			—			4,702,691			—


	2018
	Testing			Assembly			LCDD			Bumping			Others			Elimination			Total continuing operations			Total continuing operations
	NT$000			NT$000			NT$000			NT$000			NT$000			NT$000			NT$000			US$000
Revenue
External customers		4,790,097			4,679,676			5,694,720			3,315,534			—			—			18,480,027			603,725
Inter-segment		—			—			—			—			35,738			(35,738	)		—			—

Total revenue		4,790,097			4,679,676			5,694,720			3,315,534			35,738			(35,738	)		18,480,027			603,725

Timing of revenue recognition
At a point in time		—			—			—			—			35,738			(35,738	)		—			—
Over time		4,790,097			4,679,676			5,694,720			3,315,534			—			—			18,480,027			603,725

		4,790,097			4,679,676			5,694,720			3,315,534			35,738			(35,738	)		18,480,027			603,725

Operating profit (loss)		1,306,742			(207,700	)		1,226,755			(202,497	)		(23,433	)		(146	)		2,099,721			68,596
Depreciation expenses		(769,660	)		(578,205	)		(1,400,784	)		(627,412	)		(518	)		—			(3,376,579	)		(110,310	)
Interest income		—			—			—			—			49,971			—			49,971			1,633
Interest expense		—			—			—			—			(152,416	)		—			(152,416	)		(4,979	)
Share of profit (loss) of associates		—			—			—			—			(668,377	)		368,276			(300,101	)		(9,804	)
Purchase of property, plant and equipment		1,563,919			321,976			2,732,141			327,251			283			—			4,945,570			161,567

Geographic information of revenue:


	2016		2017		2018		2018
	NT$000		NT$000		NT$000		US$000
Area
ROC		12,728,014		13,152,419		14,751,766		481,926
Japan		1,855,674		2,257,296		1,825,479		59,637
Singapore		3,087,835		1,798,585		1,143,661		37,362
Others		716,070		732,555		759,121		24,800

		18,387,593		17,940,855		18,480,027		603,725

Net revenue from customers representing at least 10% of the total revenue:


	2016				2017				2018				2018
	Amount		%		Amount		%		Amount		%		Amount
	NT$000				NT$000				NT$000				US$000
Customers
Customer A		3,370,285		18		3,434,873		19		3,794,991		21		123,979
Customer K		2,633,431		14		2,742,882		15		2,637,053		14		86,150
Customer C		1,870,675		10		1,530,209		9		1,957,467		11		63,949
Customer I		3,085,190		17		1,798,111		10		1,101,956		6		36,000

The revenue generated from the above customers is mainly from the segments of Assembly and LCDD.

Contract assets and liabilities:

The Group has recognized the following contract assets and liabilities in relation to revenue from contracts with customers:


	December 31, 2018
	NT$000		US$000
Contract assets		299,835		9,795

Contract liabilities (Advance payments)		1,432		47

The Group uses operating profit (loss) as the measurement for segment profit (loss) and the basis of performance assessment. There was no material inconsistency between the accounting policies of the operating segment and the accounting policies described in Note 2.

Contract assets have increased as the Group has completed more services in excess of customer’s payment. The Group also recognized a loss allowance for contract assets following the adoption of IFRS 9, see Note 35 b) for further information.

Revenue recognized in the current reporting period amounted to NT$1,013 thousand was related to carried-forward contract liabilities but was not related to performance obligations that were satisfied in prior year.

All of the service contracts are for periods of one year or less. As permitted under IFRS 15, the transaction price allocated to these unsatisfied contracts is not disclosed. As of December 31, 2018, the Group has not recognized an asset in relation to costs to fulfil a service contract.

Operating costs and expenses

12 Months Ended

Dec. 31, 2018

Analysis of income and expense [abstract]

Operating costs and expenses

5.	*Operating costs and expenses*


	2016			2017		2018		2018
	NT$000			NT$000		NT$000		US$000
Change of finished goods and work in process		(19,498	)		31,977		—		—
Consumption of raw materials and supplies		3,346,540			3,036,350		3,079,909		100,617
Employee benefit expenses		5,317,125			5,895,778		5,606,833		183,170
Depreciation and amortization		3,089,904			2,899,278		3,376,579		110,310
Other expenses		4,745,253			4,530,425		4,464,499		145,851

Total operating costs and expenses		16,479,324			16,393,808		16,527,820		539,948

Employee benefit expenses
Salaries		4,109,393			4,847,433		4,628,039		151,194
Directors remuneration		16,810			27,276		18,456		603
Labor and health insurance		351,232			390,788		406,111		13,267
Pension		183,293			198,502		201,567		6,585
Share-based payments		356,463			123,021		41,043		1,341
Other personnel expenses		299,934			308,758		311,617		10,180

		5,317,125			5,895,778		5,606,833		183,170

Other operating income (expenses), net

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Other operating income (expenses), net

6.	*Other operating income (expenses), net*


	2016			2017			2018			2018
	NT$000			NT$000			NT$000			US$000
Gain on disposal of property, plant and equipment, net		2,575			132,777			14,274			466
Impairment on property, plant and equipment		(8,198	)		(956	)		—			—
Gain on disposal of scrapped materials		30,476			27,940			59,380			1,940
Gain on disposal of items purchased on behalf of others		48,812			26,417			31,268			1,021
Royalty income		—			11,998			43,224			1,412
Insurance compensation income		7,033			486,858			147			5
Others		9,608			7,800			(779	)		(25	)

		90,306			692,834			147,514			4,819

Finance costs

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Finance costs

7.	*Finance costs*


	2016			2017			2018			2018
	NT$000			NT$000			NT$000			US$000
Interest expenses
Bank loans		157,254			208,486			170,476			5,569
Lease obligations payable		212			708			482			16
Less: Amounts capitalized in qualifying assets		(12,921	)		(18,769	)		(18,542	)		(606	)

		144,545			190,425			152,416			4,979
Finance expense		34,571			26,858			37,832			1,236

		179,116			217,283			190,248			6,215

Other non-operating income (expenses), net

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Other non-operating income (expenses), net

8.	*Other non-operating income (expenses), net*


	2016			2017			2018		2018
	NT$000			NT$000			NT$000		US$000
Interest income
Bank deposits		38,554			53,123			49,051		1,603
Financial assets at amortized cost		—			—			920		30
Foreign exchange gains (losses), net		(195,326	)		(418,970	)		93,104		3,041
Gain on valuation of financial assets at fair value through profit or loss		621			637			1,485		49
Gain on disposal of long-term investment in associates		—			16,929			—		—
Rental income		8,203			11,075			7,819		255
Dividend income		—			—			571		19
Reimbursement of ADSs service charge		—			23,707			13,269		433
Others		—			2,808			6,851		224

		(147,948	)		(310,691	)		173,070		5,654

Income tax expense

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Income tax expense

9.	*Income tax expense*

Income tax expense arising in other jurisdictions is calculated at the rates prevailing in the relevant jurisdictions, based on existing legislation, interpretations and practices in respect thereof.

The amendment to the Income Tax Act in ROC has been approved and promulgated in February 2018 to raise the profit-seeking enterprise income tax rate from 17% to 20%, decrease the tax rate on unappropriated retained earnings from 10% to 5%, and abandon the imputation tax credit account effective from fiscal year starting January 1, 2018.

The statutory tax rates for the years ended December 31, 2016 and 2017 for ChipMOS Taiwan and Unimos Shanghai were 17% and 25%, respectively. The statutory tax rate for the year ended December 31, 2018 for ChipMOS Taiwan was 20%.

The major components of income tax expense for the years ended December 31, 2016, 2017 and 2018 are:


	2016			2017		2018			2018
	NT$000			NT$000		NT$000			US$000
Current income tax:
Current income tax on profits for the period		331,144			125,376		326,057			10,652
Income tax (benefit) on unappropriated retained earnings		(174,930	)		246,684		28,165			920
Prior year income tax under estimation		4,527			67,885		3,729			122

Total current income tax		160,741			439,945		357,951			11,694

Deferred income tax:
Relating to origination and reversal of temporary differences		16,379			110,542		101,441			3,314
Impact of change in tax rate		—			—		(2,774	)		(90	)

Total deferred income tax		16,379			110,542		98,667			3,224

Income tax expense reported in the consolidated statements of comprehensive income		177,120			550,487		456,618			14,918

Deferred tax charged to other comprehensive income:


	2016			2017		2018			2018
	NT$000			NT$000		NT$000			US$000
Unrealized gain on valuation of financial assets at fair value through other comprehensive income		—			—		17,005			556
Remeasurement of defined benefit obligations		(7,375	)		8,642		(11,992	)		(392	)
Impact of change in tax rate		—			—		(887	)		(29	)

		(7,375	)		8,642		4,126			135

Reconciliation of income tax expense and the accounting profit before income tax:


	2016			2017			2018			2018
	NT$000			NT$000			NT$000			US$000
Tax calculated based on profit before tax and statutory tax rate		214,550			566,649			356,488			11,646
Expenses disallowed (added) by tax regulations		(2,190	)		10,185			14,689			480
Temporary difference not recognized as deferred tax assets		1,306			(85,168	)		(10,951	)		(358	)
Tax exempted (income) expenses by tax regulation		12,057			(256,788	)		66,353			2,168
Taxable loss not recognized as deferred tax assets		54,012			—			—			—
Effect of different tax rates in countries in which the Group operates		10,451			1,040			919			30
Withholding tax		57,337			—			—			—
Impact of change in tax rate		—			—			(2,774	)		(90	)
Prior year income tax under estimation		4,527			67,885			3,729			122
Income tax (benefit) on unappropriated retained earnings		(174,930	)		246,684			28,165			920

Income tax expense reported in the consolidated statements of comprehensive income		177,120			550,487			456,618			14,918

The details of deferred tax assets (liabilities) are as follows:


	January 1,			Retroactive adjustment			Profit or loss			Other comprehensive income (loss)			December 31,			December 31,
	NT$000			NT$000			NT$000			NT$000			NT$000			US$000
Year of 2017
Deferred tax assets
Unrealized exchange losses		—			—			8,167			—			8,167
Loss on inventories		26,324			—			(17,192	)		—			9,132
Property, plant and equipment		80,869			—			(25,375	)		—			55,494
Deferred revenue		41,294			—			(1,809	)		—			39,485
Provisions		11,232			—			10,411			—			21,643
Net defined benefit liability		90,087			—			(2,994	)		(8,642	)		78,451

Deferred tax assets		249,806			—			(28,792	)		(8,642	)		212,372

Deferred tax liabilities
Unrealized exchange gains		(14,155	)		—			14,155			—			—
Property, plant and equipment		(78,388	)		—			(95,905	)		—			(174,293	)

Deferred tax liabilities		(92,543	)		—			(81,750	)		—			(174,293	)

Year of 2018
Deferred tax assets
Unrealized exchange losses		8,167			144			(4,736	)		—			3,575			117
Loss on inventories		9,132			(770	)		(1,130	)		—			7,232			236
Property, plant and equipment		55,494			—			8,689			—			64,183			2,097
Deferred revenue		39,485			—			(5,329	)		—			34,156			1,116
Provisions		21,643			—			(9,247	)		—			12,396			405
Net defined benefit liability		78,451			—			7,889			14,403			100,743			3,291
Investment tax credit		—			—			4,420			—			4,420			144
Others		—			—			11			—			11			1

Deferred tax assets		212,372			(626	)		567			14,403			226,716			7,407

Deferred tax liabilities
Property, plant and equipment		(174,293	)		—			(107,301	)		—			(281,594	)		(9,200	)
Contract assets		—			(8,067	)		8,067			—			—			—
Financial assets at fair value through other comprehensive income		—			(8,636	)		—			(18,529	)		(27,165	)		(887	)

Deferred tax liabilities		(174,293	)		(16,703	)		(99,234	)		(18,529	)		(308,759	)		(10,087	)

The Company has not recognized deductible and taxable temporary differences associated with investments as deferred tax assets and liabilities. As of December 31, 2017, the amounts of deductible and taxable temporary differences not recognized as deferred tax assets and liabilities were NT$28,584 thousand and NT$920,943 thousand, respectively. As of December 31, 2018, the amounts of deductible and taxable temporary differences not recognized as deferred tax assets and liabilities were nil and NT$495,154 thousand (US$16,176 thousand), respectively.

The Company’s income tax returns through 2016 have been assessed and approved by the Tax Authority.

Earnings per share ("EPS")

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Earnings per share ("EPS")

10.

Earnings per share (“EPS”)

Basic EPS amounts are calculated by dividing the profit for the year attributable to equity holders of the Company by the weighted average number of ordinary shares outstanding during the year.

Diluted EPS amounts are calculated by dividing the profit attributable to equity holders of the Company by the weighted average number of ordinary shares outstanding during the year plus the weighted average number of ordinary shares that would be issued on conversion of all the dilutive potential ordinary shares into ordinary shares.

The following reflects the income and share data used in the basic and diluted EPS computations:


	2016
	Amount after income tax			Weighted average number of ordinary shares outstanding*		Earnings per share
Basic earnings per share	NT$000			In thousands		NT$
Profit (loss) attributable to:
Equity holders of the Company
- Continuing operations		1,829,327					2.13
- Discontinued operations		(122,105	)				(0.14	)

Equity holders of the Company		1,707,222					1.99
Predecessors’ interests		(306,012	)				(0.35	)

	1,401,210			859,644		1.64

Diluted earnings per share
Employees’ compensations					3,035
Restricted shares					4,122

Profit (loss) attributable to:
Equity holders of the Company
- Continuing operations		1,829,327					2.11
- Discontinued operations		(122,105	)				(0.14	)

Equity holders of the Company		1,707,222					1.97
Predecessors’ interests		(306,012	)				(0.35	)

	1,401,210			866,801		1.62

The weighted average number of shares takes into account the weighted average effect of changes in treasury stock transaction during the year.

2017

Amount
after income
tax

Weighted average
number of ordinary
shares outstanding

Earnings
per share

Basic earnings per share

NT$000

In thousands

NT$

Profit attributable to:

Equity holders of the Company

- Continuing operations

981,929

1.16

- Discontinued operations

1,814,953

2.14

2,796,882

846,686

3.30

Diluted earnings per share

Employees’ compensations

14,034

Restricted shares

5,075

Profit attributable to:

Equity holders of the Company

- Continuing operations

981,929

1.13

- Discontinued operations

1,814,953

2.10

2,796,882

865,795

3.23

2018

Amount
after income
tax

Weighted average
number of ordinary
shares outstanding

Earnings
per share

Basic earnings per share

NT$000

In thousands

NT$

US$

Profit attributable to the equity holders of the Company

1,325,824

802,725

1.65

0.05

Diluted earnings per share

Employees’ compensations

7,626

Restricted shares

3,356

Profit attributable to the equity holders of the Company

1,325,824

813,707

1.63

0.05

Non-current financial assets at fair value through profit or loss

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Non-current financial assets at fair value through profit or loss

12.

Non-current financial assets at fair value through profit or loss


	December 31, 2018		December 31, 2018
	NT$000		US$000
Financial assets mandatorily measured at fair value through profit or loss
Foreign partnership interests		10,940		358
Valuation adjustment		531		17

		11,471		375

Amounts recognized in profit or loss in relation to the financial assets at fair value through profit or loss are listed below:


	2018		2018
	NT$000		US$000
Financial assets mandatorily measured at fair value through profit or loss
Foreign partnership interests		38		1
Beneficiary certificates*		1,396		46
Derivative instruments		51		2

		1,485		49

Beneficiary certificates represent money market funds the Company held during the reporting period. As of December 31, 2018, there were no beneficiary certificates classified as FVTPL.

No financial assets at fair value through profit or loss were pledged to others.

Information about the fair value measurement is provided in Note 35 c).

Information about the financial assets at fair value through profit or loss as of December 31, 2017 is provided in Note 41.

Non-current financial assets at fair value through other comprehensive income

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Non-current financial assets at fair value through other comprehensive income

13.

Non-current financial assets at fair value through other comprehensive income


	December 31, 2018		December 31, 2018
	NT$000		US$000
Designation of equity instruments
Foreign unlisted stocks		38,534		1,259
Valuation adjustment		135,823		4,437

		174,357		5,696

Based on the Group’s business model, the foreign unlisted stocks held for strategic investments and not for the purpose of trading were elected to classify as “Financial assets at fair value through other comprehensive income”. As of December 31, 2018, the fair value of aforementioned investments was NT$174,357 thousand (US$5,696 thousand). For the year ended December 31, 2018, dividend income recognized related to investments held at the end of the reporting period was NT$571 thousand (US$19 thousand).

Amounts recognized in other comprehensive income in relation to the financial assets at fair value through other comprehensive income are listed below:


	2018		2018
	NT$000		US$000
Financial assets at fair value through other comprehensive income
Foreign unlisted stocks		85,022		2,778

No financial assets at fair value through other comprehensive income were pledged to others.

Information about the fair value measurement is provided in Note 35 c).

Information about the financial assets at fair value through other comprehensive income as of December 31, 2017 is provided in Note 41.

Investment in associates

12 Months Ended

Dec. 31, 2018

Investments accounted for using equity method [abstract]

Investment in associates

14.

Investment in associates

Details of investment in associates are as follows:

Country of
incorporation
and business

Measurement
method

December 31, 2017

December 31, 2018

Investee company

Carrying
amount

Ownership

Carrying
amount

Ownership

NT$000

US$000

JMC ELECTRONICS CO., LTD. (“JMC”)

Kaohsiung,
Taiwan

Equity
method

373,276

19.10

406,792

13,290

19.10

Unimos Shanghai

Shanghai,

People’s
Republic
of China

Equity
method

3,060,056

45.02

3,456,949

112,935

45.02

On November 30, 2016, the Company’s Board of Directors adopted a resolution to authorize its subsidiary, ChipMOS BVI, to dispose 54.98% of Unimos Shanghai’s equity. The equity transfer was completed in March 2017, and subsequently, due to the loss of control but retention of significant influence, Unimos Shanghai was excluded from the consolidated financial statements and was accounted for as an “Investment in associate”. Information is provided in Note 20.

In January 2017, the Company did not participate in the capital increase of JMC, which reduced the Company’s shareholding from 21.22% to 19.10%. Given that the Company still retains significant influence by holding two seats in JMC’s Board of Directors, JMC was still recognized as “Investment in associates”. As a result of the change in shareholding, the Company recognized disposal gain from long-term investment amounted to NT$16,929 thousand for the year ended December 31, 2017.

In June 2017 and January 2018, ChipMOS BVI participated in Unimos Shanghai’s increase of paid-in capital based on its shareholding amounted to NT$1,373,486 thousand and NT$794,694 thousand (US$25,962 thousand), respectively.

For the years ended December 31, 2017 and 2018, the Company recognized its share of loss of investments in associates amounted to NT$179,491 thousand and NT$300,101 thousand (US$9,804 thousand), respectively.

The tables below provide summarized financial information for the investment in associates that are material to the Group.

Statements of financial position


	JMC
	December 31, 2017			December 31, 2018			December 31, 2018
	NT$000			NT$000			US$000
Current assets		843,636			1,106,789			36,158
Non-current assets		1,161,620			1,699,498			55,521
Current liabilities		(294,302	)		(817,697	)		(26,714	)
Non-current liabilities		(1,756	)		(103,922	)		(3,395	)

Total net assets		1,709,198			1,884,668			61,570

Group’s share		326,456			359,972			11,760
Goodwill		46,820			46,820			1,530

Carrying amount		373,276			406,792			13,290

Statements of financial position


	Unimos Shanghai
	December 31, 2017			December 31, 2018			December 31, 2018
	NT$000			NT$000			US$000
Current assets		3,380,641			3,946,082			128,915
Non-current assets		2,766,839			3,254,687			106,328
Current liabilities		(460,054	)		(554,160	)		(18,104	)
Non-current liabilities		(489,097	)		(442,306	)		(14,450	)

Total net assets		5,198,329			6,204,303			202,689

Group’s share		2,340,506			2,793,438			91,259
Depreciable assets		703,536			644,718			21,062
Goodwill		22,118			22,118			723
Inter-company transactions and amortization		(6,104	)		(3,325	)		(109	)

Carrying amount		3,060,056			3,456,949			112,935

Statements of comprehensive income

JMC

Year ended December 31,

2016

2017

2018

NT$000

US$000

Revenue

1,667,761

1,322,928

1,931,008

63,084

Profit for the year from continuing operations

136,303

4,414

219,544

7,172

Other comprehensive income (loss), net of income tax

(627

)

2,903

(14,074

)

(460

)

Total comprehensive income

135,676

7,317

205,470

6,712

Dividend received from the associate

5,730

14,325

5,730

187


	Unimos Shanghai
	Year ended December 31,
	2017			2018			2018
	NT$000			NT$000			US$000
Revenue		1,141,415			1,334,196			43,587

Loss for the year from continuing operations		(348,472	)		(629,303	)		(20,559	)
Other comprehensive income, net of income tax		—			—			—

Total comprehensive loss		(348,472	)		(629,303	)		(20,559	)

Dividend received from the associate		—			—			—

According to IFRS 5 “Non-current Assets Held for Sale and Discontinued Operations”, total comprehensive income of Unimos Shanghai for the three months ended March 31, 2017 was included in the Group’s consolidated statement of comprehensive income with the adjustments of ceasing to recognize depreciation and amortization expenses and the elimination of inter-company transactions. Information about discontinued operations is provided in Note 20.

Financial assets at amortized cost

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Financial assets at amortized cost

15.

Financial assets at amortized cost


	December 31, 2018		December 31, 2018
	NT$000		US$000
Current
Time deposits		169,168		5,526

Non-current
Time deposits		30,715		1,003
Restricted bank deposits		68,388		2,234

		99,103		3,237

Amounts recognized in profit or loss in relation to financial assets at amortized cost are listed below:


	2018		2018
	NT$000		US$000
Interest income		920		30

As of December 31, 2018, without taking into account any collateral held or other credit enhancements, the maximum exposure to credit risk in respect of the amount that best represents the financial assets at amortized cost held by the Group was NT$268,271 thousand (US$8,763 thousand).

Information about the financial assets at amortized cost that were pledged to others as collateral is provided in Note 34.

Information relating to credit risk of financial assets at amortized cost is provided in Note 35 b).

Property, plant and equipment, net

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Property, plant and equipment, net

16.

Property, plant and equipment, net


	Land		Buildings			Machinery and equipment			Tools			Other equipment			Construction in progress and equipment to be inspected			Total			Total
	NT$000		NT$000			NT$000			NT$000			NT$000			NT$000			NT$000			US$000
January 1, 2017
Cost		452,738		11,183,278			47,002,228			3,999,894			3,353,413			1,627,816			67,619,367
Accumulated depreciation and impairment		—		(6,395,332	)		(39,430,608	)		(3,475,451	)		(2,786,790	)		—			(52,088,181	)

		452,738		4,787,946			7,571,620			524,443			566,623			1,627,816			15,531,186
Less: Property, plant and equipment classified as held for sale		—		(710,191	)		(433,688	)		(90,460	)		(168,314	)		(631,315	)		(2,033,968	)

		452,738		4,077,755			7,137,932			433,983			398,309			996,501			13,497,218

January 1, 2017		452,738		4,077,755			7,137,932			433,983			398,309			996,501			13,497,218
Additions		—		211,098			2,007,767			571,601			195,957			1,716,268			4,702,691
Disposals		—		—			(30,066	)		(2,302	)		(1,865	)		—			(34,233	)
Reclassifications		—		141,400			1,535,619			44,882			22,149			(1,744,050	)		—
Depreciation expenses		—		(511,167	)		(1,837,482	)		(357,695	)		(192,934	)		—			(2,899,278	)
Impairment losses		—		—			—			—			(956	)		—			(956	)
Exchange adjustments		—		—			(43	)		—			(88	)		—			(131	)

December 31, 2017		452,738		3,919,086			8,813,727			690,469			420,572			968,719			15,265,311

December 31, 2017
Cost		452,738		9,809,970			45,778,207			4,004,703			2,624,083			968,719			63,638,420
Accumulated depreciation and impairment		—		(5,890,884	)		(36,964,480	)		(3,314,234	)		(2,203,511	)		—			(48,373,109	)

		452,738		3,919,086			8,813,727			690,469			420,572			968,719			15,265,311

January 1, 2018
Cost		452,738		9,809,970			45,778,207			4,004,703			2,624,083			968,719			63,638,420			2,079,008
Accumulated depreciation and impairment		—		(5,890,884	)		(36,964,480	)		(3,314,234	)		(2,203,511	)		—			(48,373,109	)		(1,580,304	)

		452,738		3,919,086			8,813,727			690,469			420,572			968,719			15,265,311			498,704

January 1, 2018		452,738		3,919,086			8,813,727			690,469			420,572			968,719			15,265,311			498,704
Additions		—		247,186			2,445,313			591,229			172,652			1,489,190			4,945,570			161,567
Disposals		—		—			(904	)		(11,745	)		(2,067	)		—			(14,716	)		(481	)
Reclassifications		—		199,724			1,154,663			7,604			26,026			(1,388,017	)		—			—
Depreciation expenses		—		(457,265	)		(2,180,718	)		(535,378	)		(203,218	)		—			(3,376,579	)		(110,310	)
Exchange adjustments		—		—			12			—			23			—			35			1

December 31, 2018		452,738		3,908,731			10,232,093			742,179			413,988			1,069,892			16,819,621			549,481

December 31, 2018
Cost		452,738		10,254,531			48,274,171			4,402,711			2,610,893			1,069,892			67,064,936			2,190,948
Accumulated depreciation and impairment		—		(6,345,800	)		(38,042,078	)		(3,660,532	)		(2,196,905	)		—			(50,245,315	)		(1,641,467	)

		452,738		3,908,731			10,232,093			742,179			413,988			1,069,892			16,819,621			549,481

As of December 31, 2017 and 2018, certain of the above property, plant and equipment were pledged as collateral for long-term bank loans (Notes 34).

Amount of borrowing costs capitalized as part of property, plant and equipment and the range of the interest rates for such capitalization are as follows:


	2017		2018		2018
	NT$000		NT$000		US$000
Capitalization interest		18,769		18,542		606
Capitalization interest rate applied		1.7624%		1.7582%		1.7582%

Inventories

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Inventories

17.

Inventories


	December 31, 2017
	Cost		Allowance for impairment losses			Carrying amount
	NT$000		NT$000			NT$000
Raw materials		1,769,917		(49,183	)		1,720,734
Work in process		180,252		(4,163	)		176,089
Finished goods		32,784		(368	)		32,416

		1,982,953		(53,714	)		1,929,239

December 31, 2018

Cost

Allowance for
impairment losses

Carrying amount

NT$000

US$000

Raw materials

1,814,992

(36,157

)

1,778,835

58,113

The cost of inventories recognized as an expense for the year:


	2017			2018			2018
	NT$000			NT$000			US$000
Cost of revenue		14,766,555			15,057,605			491,918
Loss on abandonment		38,301			5,497			179
Reversal of inventory valuation and obsolescence loss		(101,127	)		(13,070	)		(427	)

		14,703,729			15,050,032			491,670

Raw materials are utilized throughout the course of provision of semiconductor bumping, assembly and testing services. Items used for manufacturing and product sales are insignificant.

Reversal of inventory valuation and obsolescence loss was recognized due to the change in net realizable market value.

As of December 31, 2017 and 2018, no inventories were pledged.

Accounts and notes and other receivables

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Accounts and notes and other receivables

18.

Accounts and notes and other receivables


	December 31, 2017		December 31, 2018			December 31, 2018
	NT$000		NT$000			US$000
Accounts receivable		4,013,705		4,747,834			155,108
Notes receivable		2,029		1,595			52
Less: Loss allowance		—		(2,141	)		(70	)

		4,015,734		4,747,288			155,090

Other receivables		56,716		63,049			2,060
Less: Loss allowance		—		(12	)		(1	)

		56,716		63,037			2,059

		4,072,450		4,810,325			157,149

As of December 31, 2017 and 2018, no accounts and notes and other receivables were pledged.

The Group’s credit term granted to customers is 30~90 days. Receivables do not bear interest. The loss allowance is determined based on the credit quality of customers. Information relating to credit risk is provided in Note 35 b).

The aging analysis of accounts receivable based on past due date is as follows:


	December 31, 2017		December 31, 2018		December 31, 2018
	NT$000		NT$000		US$000
Current		3,997,833		4,595,300		150,124
Within 1 month		10,482		18,807		615
1 – 2 months		477		131,787		4,305
2 – 3 months		426		1,436		47
3 – 4 months		1,431		180		6
Over 4 months		3,056		324		11

		4,013,705		4,747,834		155,108

Without taking into account of any collateral held or other credit enhancements, the amount that best reflects the Group’ maximum exposure to credit risk in respect of the accounts receivable is the carrying amount at the end of each reporting period.

Cash and cash equivalents

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Cash and cash equivalents

19.

Cash and cash equivalents


	December 31, 2017		December 31, 2018		December 31, 2018
	NT$000		NT$000		US$000
Short-term deposits		3,883,614		3,245,750		106,036
Cash		470		470		15
Cash at banks		4,151,630		1,396,302		45,616

		8,035,714		4,642,522		151,667

Cash at banks earns interest at floating rates based on daily bank deposit rates. Short-term deposits are made for varying periods of between 31 days and 3 months, depending on the immediate cash requirements of the Group, and earn interest at the respective short-term deposit rates.

As of December 31, 2017 and 2018, no cash and cash equivalents were pledged.

Non-current assets held for sale and discontinued operations

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Non-current assets held for sale and discontinued operations

20.

Non-current assets held for sale and discontinued operations

The assets and liabilities related to Unimos Shanghai have been classified as non-current assets held for sale and liabilities directly related to non-current assets held for sale and presented as discontinued operations for meeting the definition of discontinued operations following the resolution of the Company’s Board of Directors on November 30, 2016 to sell 54.98% of Unimos Shanghai’s equity interest. The transaction was completed in March 2017, and subsequently, due to the loss of control but retention of significant influence, Unimos Shanghai was excluded from the consolidated financial statements and recorded as “Investments in associates”. As of December 31, 2017 and 2018, there were no related assets and liabilities of disposal group classified as held for sale. Please refer to Note 14 for more details.

In March 2017, the Company received NT$2,230,544 thousand in cash and recognized total gain on disposal of discontinued operations amounted to NT$1,843,234 thousand. Based on the fair value received and the book value of its investment, gain on disposal of 54.98% equity interest is equal to NT$999,630 thousand and gain on fair value remeasurement of 45.02% retained investment is equal to NT$843,604 thousand.

The cash flow information of the discontinued operations is as follows:


	2016			2017
	NT$000			NT$000
Net cash used in operating activities		(1,109,029	)		(109,079	)
Net cash used in investing activities		(1,331,564	)		(272,925	)
Net cash generated from financing activities		1,463,664			461,312
Effect of foreign exchange rate changes		(61,336	)		(19,874	)

Net increase (decrease) in cash and cash equivalents		(1,038,265	)		59,434

Equity of disposal group classified as amounts recognized in other comprehensive income and accumulated in equity relating to non-current assets held for sale :


	December 31,
	2016
	NT$000
Foreign currency translation reserve		287,645

Cumulative income or expense recognized in other comprehensive income relating to disposal group classified as held for sale:


	2016			2017
	NT$000			NT$000
Exchange differences on translation of foreign operations		(195,972	)		(287,645	)

The results of discontinued operations are as follows:


	2016			2017
	NT$000			NT$000
Revenue		1,005,166			227,095
Cost of revenue		(986,004	)		(195,078	)
Operating expenses		(179,178	)		(58,840	)
Other operating income (expenses), net		13,753			1,429
Non-operating income (expenses), net		24,158			(2,887	)

Loss from discontinued operations before income tax		(122,105	)		(28,281	)
Income tax expense		—			—

Loss from discontinued operations after income tax		(122,105	)		(28,281	)
Gain on disposal of discontinued operations		—			1,843,234

Profit (loss) from discontinued operations		(122,105	)		1,814,953

Discontinued operations’ revenue is mainly from the segments of testing and assembly.

Issued capital

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Issued capital

21.

Issued capital

December 31,
2016

December 31,
2017

December 31,
2018

in thousands

Authorized shares

Ordinary shares

1,450,000

970,000

December 31,
2016

December 31,
2017

December 31,
2018

in thousands

Ordinary shares issued and fully paid

Ordinary shares

886,966

886,297

752,858

Issued capital (NT$000)

8,869,663

8,862,971

7,528,577

(US$245,952
thousand

)

The par value of ordinary shares issued was NT$10 per share.

The movement of ordinary shares issued is set out below:


	2016			2017			2018
	in thousands			in thousands			in thousands
January 1		896,206			886,966			886,297
Restricted shares		435			—			—
Unearned restricted shares – cancelled		—			(669	)		(502	)
Share cancellation		—			—			(4,515	)
Issuance of ordinary shares for capital reorganization (Note 31)		512,405			—			—
Cancellation of ordinary shares from capital reorganization (Note 31)		(522,080	)		—			—
Capital reduction		—			—			(128,422	)

December 31		886,966			886,297			752,858

On February 4, 2016 and May 12, 2016, the Board of Directors of the Company approved the share repurchase programs for repurchase of ordinary shares by the Company of up to NT$600 million and NT$600 million, respectively. As of December 31, 2016 and 2017, 30,000 thousand shares were repurchased and recorded as treasury stock.

On October 31, 2016, the Company’s former parent company, ChipMOS Bermuda was merged with and into the Company, with the latter being the surviving company. Please refer to Note 31 for details of the capital reorganization. Pursuant to the Merger, the Company issued 21,775,257 units of ADSs (25,620,267 units of ADSs before capital reduction adjustment), which were listed on the NASDAQ Global Select Market, and each ADS represents 20 ordinary shares of the Company. As of December 31, 2018, the outstanding ADSs were approximately 5,309,826 units representing 106,197 thousand ordinary shares of the Company. The major terms and conditions of the ADSs are summarized as follows:

Voting rights:

ADS holders will have no right to directly vote in shareholders’ meetings with respect to the deposited shares. The depository bank shall vote on behalf of the ADS holders or provide voting instruction to the designated person of the Company. The depository bank shall vote in the manner as instructed by ADS holders.

Distribution of dividends:

ADS holders are deemed to have the same rights as holders of ordinary shares with respect to the distribution of dividends.

In order to adjust capital structure and increase return of equity, the Company’s shareholders adopted a resolution on June 26, 2018 to reduce capital stock and return cash to shareholders. Subsequently, the record date of the capital reduction was fixed on August 15, 2018, and capital was reduced approximately 15% amounted to NT$1,329,446 thousand (US$43,432 thousand) consisting of 132,945 thousand ordinary shares.

Capital surplus and retained earnings

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Capital surplus and retained earnings

22.

Capital surplus and retained earnings

The reconciliation between the opening and closing balances of each component of the Group’s consolidated equity is set out in the consolidated statements of changes in equity.

Capital surplus

Details of the Group’s capital surplus are set out below:


	December 31, 2016		December 31, 2017		December 31, 2018		December 31, 2018
	NT$000		NT$000		NT$000		US$000
Share premium		6,473,471		5,873,743		5,873,743		191,890
Restricted shares		408,051		390,401		382,506		12,496
Others		7,304		7,304		7,304		239

		6,888,826		6,271,448		6,263,553		204,625

Pursuant to the ROC Company Act, any capital surplus arising from paid-in capital in excess of par value on issuance of ordinary shares and donations can be used to cover accumulated deficits or to issue new stocks or cash to shareholders in proportion to their share ownership, provided that the Company has no accumulated deficits. Furthermore, the ROC Securities and Exchange Act requires that the amount of capital surplus to be capitalized mentioned above may not exceed 10% of the paid-in capital each year. Capital surplus may not be used to cover accumulated deficits unless the legal reserve is insufficient.

Retained earnings

(a)

According to the Company’s Articles of Incorporation, current year’s earnings before tax, if any, shall be distributed in the following order:

Pay all taxes and duties;

ii)

Offset prior years’ operating losses, if any;

iii)

Set aside 10% of the remaining amount after deducting i) and ii) as legal reserve;

iv)

Appropriate or reverse a certain amount as special reserve according to the relevant regulations;

After items i), ii), iii) and iv) were deducted, the remaining amount may be distributed as shareholders’ dividend.

(b)

The Company’s dividend policy is summarized below: as the Company operates in a volatile business environment, the dividend is distributed taking into consideration the Company’s financial structure, operating results and future expansion plans. The earnings distribution of the Company may be made by way of cash dividends or stock dividends; provided that cash dividends shall account for at least 10% of the total dividends distributed. The earnings distribution will be proposed by the Board of Directors and approved at the shareholders’ meeting.

(c)

Legal reserve can only be used to offset deficits or increase capital in issuing ordinary shares or in distribution cash. The amount of legal reserve that may be used to increase capital or distribute cash shall be limited to the portion of the reserve balance exceeding 25% of the capital stock.

(d)

In accordance with the regulations, the Company must set aside a special reserve from the debit balance on other equity items at the statements of financial position date before distributing earnings. When the debit balance on other equity items is reversed subsequently, the reversed amount may be included in the distributable earnings.

(e)

The distribution of 2015, 2016 and 2017 were resolved at the shareholders’ meetings on May 31, 2016, May 26, 2017 and June 26, 2018, respectively. Details are summarized below:


	2015				2016				2017
	Amount		Distribution per share		Amount		Distribution per share		Amount		Distribution per share
	NT$000		NT$		NT$000		NT$		NT$000		NT$
Legal reserve		223,047				28,680				302,653
Cash dividend		1,792,553		2.09		257,026		0.30		256,806		0.30
Cash distribution from capital surplus		—		—		599,728		0.70		—		—

Treasury stock

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Treasury stock

23.

Treasury stock

The movement of treasury stock is set out below:


	2016				2017				2018
	Shares (in thousands)		Amount (NT$000)		Shares (in thousands)		Amount (NT$000)		Shares (in thousands)			Amount (NT$000)			Amount (US$000)
January 1		—		—		30,085		1,007,654		30,085			1,007,654			32,919
Treasury stock (repurchased)		30,085		1,007,654		—		—		—			—			—
Capital reduction		—		—		—		—		(4,515	)		(45,151	)		(1,475	)

December 31		30,085		1,007,654		30,085		1,007,654		25,570			962,503			31,444

Pursuant to the ROC Securities and Exchange Act, the number of shares repurchased as treasury stock should not exceed 10% of the number of the Company’s issued shares and the amount repurchased may not exceed the sum of retained earnings, paid-in capital in excess of par value and realized capital surplus.

Pursuant to the ROC Securities and Exchange Act, treasury stock may not be pledged as collateral and is not entitled to dividends before it is reissued.

Pursuant to the ROC Securities and Exchange Act, treasury stock should be reissued to the employees within three years from the reacquisition date and shares not reissued within the three-year period are to be retired. Treasury stock to enhance the Company’s credit rating and the stockholders’ equity should be retired within six months from acquisition.

Bank loans

12 Months Ended

Dec. 31, 2018

Long-term bank loans [Member]

Statement [LineItems]

Bank loans

24.

Long-term bank loans


Type of loans	Period and payment term	December 31, 2017			December 31, 2018			December 31, 2018
		NT$000			NT$000			US$000
Syndicated bank loan	Borrowing period is from May 30, 2018 to May 30, 2023; interest is repayable monthly; principal is repayable semi-annually from November 30, 2018		—			9,822,000			320,876
Syndicated bank loan	Borrowing period is from June 30, 2016 to June 30, 2021; interest is repayable monthly; principal is repayable semi-annually from December 30, 2017		9,675,301			—			—
Less: Fee on syndicated bank loan			(33,280	)		(32,482	)		(1,061	)
Less: Current portion (fee included)			(2,143,168	)		(747,422	)		(24,418	)

			7,498,853			9,042,096			295,397

Interest rate range			1.7895%			1.7895%			1.7895%

Unused credit lines of long-term bank loans NT$000			2,400,000			1,800,000

On May 15, 2018, the Company entered into a syndicated loan with eleven banks in Taiwan, including Taiwan Cooperative Bank, in the amount of NT$12 billion with a term of five years. Funding from this syndicated loan was used to repay the existing debt of financial institutions and broaden the Company’s working capital. Pursuant to the syndicated loan agreement, the Group is required to maintain certain financial ratios including current ratio, interest protection multiples and debt to equity ratio during the loan periods.

On May 16, 2016, the Company entered into a syndicated loan with ten banks in Taiwan, including Land Bank of Taiwan, in the amount of NT$13.2 billion with a term of five years. Funding from this syndicated loan was used to repay the prior syndicated loan in 2014 and broaden the Company’s working capital. Pursuant to the syndicated loan agreement, the Group is required to maintain certain financial ratios including current ratio, interest protection multiples and debt to equity ratio during the loan periods. The syndicated loan was fully repaid in May 2018.

As of December 31, 2017 and 2018, the Group was in compliance with the financial ratio requirements.

The Group’s bank loans are mortgaged by certain land, buildings and equipment as collateral (Note 34).

Details of the repayment schedule in respect of the bank loans are as follows:

December 31,
2017

December 31,
2018

NT$000

US$000

Within 1 year

2,143,168

747,422

24,418

1 to 5 years

7,498,853

9,042,096

295,397

9,642,021

9,789,518

319,815

Short-term bank loans [member]

Statement [LineItems]

Bank loans

29.

Short-term bank loans

December 31,
2017

December 31,
2018

NT$000

US$000

Unsecured bank loans

969,353

—

Interest rate range

0.55%~1.71%

—

Unused credit lines of short-term bank loans are as follows:


	December 31, 2017		December 31, 2018
NT$000		3,028,357		3,252,500
US$000		80,000		90,000

Retirement benefit plans

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Retirement benefit plans

25.

Retirement benefit plans

Defined benefit plans

(a)

The Company has a defined benefit pension plan in accordance with the Labor Standards Act, covering all regular employees’ service years prior to the enforcement of the Labor Pension Act on July 1, 2005 and service years thereafter of employees who chose to continue to be subject to the pension mechanism under the Labor Standards Act. Under the defined benefit pension plan, two units are accrued for each year of service for the first 15 years and one unit for each additional year thereafter, subject to a maximum of 45 units. Pension benefits are based on the number of units accrued and the average monthly salaries and wages of the last 6 months prior to retirement.

The Company contributes monthly an amount equal to 2% of the employees’ monthly salaries and wages to the pension fund deposited with Bank of Taiwan, the trustee, under the name of the independent pension fund committee. Also, the Company would assess the balance in the aforementioned labor pension reserve account by the end of every year. If the account balance is insufficient to pay the pension calculated by the aforementioned method, to the employees expected to be qualified for retirement next year, the Company will make contribution to cover the deficit by March of following year.

(b)

The amounts recognized in the statements of financial position are as follows:


	December 31, 2017			December 31, 2018			December 31, 2018
	NT$000			NT$000			US$000
Present value of defined benefit obligations		(838,543	)		(910,081	)		(29,731	)
Fair value of plan assets		360,017			389,316			12,718

Net defined benefit liability		(478,526	)		(520,765	)		(17,013	)

(c)

Movements in net defined benefit liability are as follows:


	2017
	Present value of defined benefit obligations			Fair value of plan assets			Net defined benefit liability
	NT$000			NT$000			NT$000
January 1		(894,163	)		347,195			(546,968	)
Current service cost		(386	)		—			(386	)
Interest (expense) income		(13,236	)		5,226			(8,010	)

		(907,785	)		352,421			(555,364	)

Remeasurements:
Return of plan assets (excluding the amount included in interest income or expense)		—			(1,842	)		(1,842	)
Financial assumption movement effect		28,506			—			28,506
Experience adjustments		24,174			—			24,174

		52,680			(1,842	)		50,838

Pension fund contribution		—			26,000			26,000
Paid pension		16,562			(16,562	)		—

December 31		(838,543	)		360,017			(478,526	)


	2018
	Present value of defined benefit obligations			Fair value of plan assets			Net defined benefit liability
	NT$000			NT$000			NT$000			US$000
January 1		(838,543	)		360,017			(478,526	)		(15,633	)
Current service cost		(382	)		—			(382	)		(12	)
Interest (expense) income		(14,429	)		6,291			(8,138	)		(266	)

		(853,354	)		366,308			(487,046	)		(15,911	)

Remeasurements:
Return of plan assets (excluding the amount included in interest income or expense)		—			8,145			8,145			266
Financial assumption movement effect		(56,934	)		—			(56,934	)		(1,860	)
Experience adjustments		(11,172	)		—			(11,172	)		(365	)

		(68,106	)		8,145			(59,961	)		(1,959	)

Pension fund contribution		—			26,242			26,242			857
Paid pension		11,379			(11,379	)		—			—

December 31		(910,081	)		389,316			(520,765	)		(17,013	)

(d)

The Bank of Taiwan was commissioned to manage the fund of the Company’s defined benefit pension plan in accordance with the fund’s annual investment and utilization plan and the “Regulations for Revenues, Expenditures, Safeguard and Utilization of the Labor Retirement Fund” (Article 6: The scope of utilization for the fund includes deposit in domestic or foreign financial institutions, investment in domestic or foreign listed, over-the-counter, or private placement equity securities, investment in domestic or foreign real estate securitization products, etc.). With regard to the utilization of the fund, its minimum earnings in the annual distributions on the final financial statements shall be no less than the earnings attainable from the amounts accrued from two-year time deposits with the interest rates offered by local banks. If the earning is less than aforementioned rates, government shall make payment for the deficit after authorized by the authority. The Company has no right to participate in managing and operating that fund and hence the Company is unable to disclose the classification of the fair value of plan asset in accordance with IAS 19 “Employee Benefits” paragraph 142. The constitution of fair value of plan assets as of December 31, 2017 and 2018 is given in the Annual Labor Retirement Fund Utilization Report announced by the government.

(e)

The principal actuarial assumptions used were as follows:


	2017		2018
Discount rate		1.75%		1.25%
Future salary increases		3.50%		3.50%

Assumptions regarding future mortality are set based on actuarial advice in accordance with published statistics and experience in each territory.

Because the main actuarial assumption changed, the present value of defined benefit obligations is affected. The sensitivity analysis of present value of defined benefit obligations effected by the changes of significant actuarial assumptions at December 31, 2017 and 2018 are shown below:


	Discount rate					Future salary increase
	Increase 0.25%			Decrease 0.25%		Increase 0.25%		Decrease 0.25%
December 31, 2017
Effect on present value of defined benefit obligations		(27,192	)		28,506		27,955		(26,816	)

December 31, 2018
Effect on present value of defined benefit obligations		(29,052	)		30,430		29,692		(28,513	)

The sensitivity analysis above is based on a change in an assumption while holding all other assumptions constant. In practice, changes in some of the assumptions may be correlated. The method of sensitivity analysis and the method of calculating net defined benefit liability in the statements of financial position are the same.

(f)

The Company expects to make contributions of NT$27,160 thousand (US$887 thousand) during 2019.

(g)

As of December 31, 2018, the weighted average duration of that retirement plan is 13.2 years. The analysis of timing of the future pension payment is as follows:


	December 31, 2018
	NT$000		US$000
Within 1 year		32,904		1,075
1-2 years		35,835		1,170
2-5 years		105,665		3,452
5-10 years		189,400		6,188

		363,804		11,885

Defined contribution plans

Effective July 1, 2005, the Company established a defined contribution pension plan (the “New Plan”) under the Labor Pension Act, covering all regular employees with ROC nationality. Under the New Plan, the Company contributes monthly an amount based on 6% of the employees’ monthly salaries and wages to the employees’ individual pension accounts at the Bureau of Labor Insurance. The benefits accrued are paid monthly or in lump sum upon termination of employment. The pension costs under defined contribution pension plans of the Company for the years ended December 31, 2017 and 2018 were NT$190,106 thousand and NT$193,047 thousand (US$6,307 thousand), respectively.

Other Payables

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Other Payables

26.

Other Payables


	December 31, 2017		December 31, 2018		December 31, 2018
	NT$000		NT$000		US$000
Salaries and bonus payable		601,239		595,575		19,457
Interest payable		2,854		963		31
Pension payable		32,402		32,038		1,047
Employees’ compensation payable		371,912		212,391		6,939
Directors’ remuneration payable		18,596		9,951		325
Other expense payable		953,179		827,564		27,036

		1,980,182		1,678,482		54,835

Current provisions

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Current provisions

27.

Current provisions

Movements in provisions are as follows:


	2018
	Provisions for deficiency compensation
	NT$000			US$000
January 1		57,155			1,867
Provision		14,211			465
Reversal		(24,451	)		(799	)
Payment		(17,563	)		(574	)

December 31		29,352			959

By adopting IFRS 15, the Group’s provision for sales allowance is presented as “Current refund liabilities” from January 1, 2018, which was previously presented as “Current provisions”. Information is provided in Note 28.

Please refer to Note 2 e) for detailed information of provisions for deficiency compensation.

Current refund liabilities

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Current refund liabilities

28.

Current refund liabilities

Movements in refund liabilities are as follows:


	2018
	Provisions for sales allowance
	NT$000			US$000
January 1		70,156			2,292
Provision		44,950			1,468
Reversal		(7,413	)		(242	)
Payment		(75,066	)		(2,452	)

December 31		32,627			1,066

Please refer to Note 2 e) for detailed information of refund liabilities.

Significant commitments and contingencies

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Significant commitments and contingencies

30.

Significant commitments and contingencies

Operating leases commitments

ChipMOS Taiwan entered into several operating lease contracts for land. These renewable operating leases will expire by 2032 and 2034.

ChipMOS USA entered into several operating lease contracts for office space. These renewable operating leases will expire by 2019 and 2020.

Future minimum lease obligation payable under those leases are as follows:


	December 31, 2017		December 31, 2018		December 31, 2018
	NT$000		NT$000		US$000
Within 1 year		39,342		68,631		2,242
1 to 5 years		130,182		140,137		4,578
Over 5 years		139,899		111,446		3,641

		309,423		320,214		10,461

Capital commitments

Capital expenditures that are contracted for, but not provided for are as follows:

December 31,
2017

December 31,
2018

NT$000

US$000

Property, plant and equipment

2,178,262

2,508,797

81,960

Other commitments

A letter of guarantee was issued by Bank of Taiwan to the Customs Administration of the Ministry of Finance for making payment of customs-duty deposits when importing. The amount of letter of guarantee will occupy the credit lines for short-term loans of ChipMOS Taiwan. As of December 31, 2017 and 2018, the amount of NT$97,500 thousand and NT$97,500 thousand (US$3,185 thousand), respectively are guaranteed by Bank of Taiwan.

As described in Note 31, as of October 31, 2016, the Company merged with its former parent company, ChipMOS Bermuda and as a result, the Company deducted unappropriated retained earnings by NT$5,052,343 thousand. The Company has filed an application to the National Taxation Bureau of the Northern Area, Ministry of Finance to apply the accumulated deficit amount, derived from subtracting the aforementioned amount from unappropriated retained earnings generated prior to year 2015 (not including 2015 unappropriated retained earnings), as a deduction in the calculation of years 2015 and 2016 additional 10% tax on unappropriated retained earnings.

Capital reorganization

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Capital reorganization

31.

Capital reorganization

To integrate resources, the Company’s former parent company, ChipMOS Bermuda, was merged with and into the Company as of October 31, 2016, the record date of the Merger, with the latter being the surviving entity and ChipMOS Bermuda being the dissolved entity. Under the Merger Agreement, each shareholder of ChipMOS Bermuda is entitled to receive, with respect to each ChipMOS Bermuda share, 0.9355 units of the Company’s newly-issued ADSs trading on the NASDAQ Global Select Market (each ADS unit represents 20 shares of the Company’s ordinary shares) and US$3.71 in cash. The Company issued 21,775,257 units of ADSs (25,620,267 units of ADSs representing 512,405 thousand ordinary shares before capital reduction adjustment) and paid US$101,657 thousand in cash (equivalent to NT$3,208,310 thousand) as the total consideration. In addition, the Company paid NT$133,311 thousand directly attributable transaction cost for the capital reorganization. As the result, the Company paid NT$3,341,621 thousand in cash for the capital reorganization.

The Company issued 512,405 thousand shares for the capital reorganization, and reduced capital by cancelling 522,080 thousand shares originally held by ChipMOS Bermuda. After the capital reorganization, the Company’s shares was net decreased by 9,675 thousand shares. When cancelling treasury stocks, the Company deducted capital surplus equal to the proportion of cancelled shares. Due to the deficit in capital surplus, the Company deducted unappropriated retained earnings by NT$5,052,343 thousand.

As of October 30, 2016, the ending balance of “Predecessors’ interests” was NT$1,692,918 thousand, which represents ChipMOS Bermuda’s net assets as if it had always been combined. The amount has been eliminated in the record date of the Merger.

Supplementary cash flow information

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Supplementary cash flow information

32.

Supplementary cash flow information

Partial cash paid for investing and financing activities

Property, plant and equipment


	2016			2017			2018			2018
	NT$000			NT$000			NT$000			US$000
Purchase in property, plant and equipment		4,690,995			4,849,331			4,945,570			161,567
Add: Beginning balance of payable to contractors and equipment suppliers		523,962			839,983			713,313			23,303
Add: Beginning balance of lease payable		—			94,952			29,842			975
Less: Ending balance of payable to contractors and equipment suppliers		(647,486	)		(878,065	)		(1,516,735	)		(49,550	)
Less: Ending balance of lease payable		(96,006	)		(84,192	)		(17,792	)		(581	)
Less: Transfer from prepaid equipment (shown as “Other non-current assets”)		—			(139,304	)		—			—

Cash paid for acquisition of property, plant and equipment		4,471,465			4,682,705			4,154,198			135,714

Capital reorganization


	2016			2017		2018		2018
	NT$000			NT$000		NT$000		US$000
Net assets acquired from ChipMOS Bermuda		12,987,736			—		—		—
Less: Issuance of shares		(9,779,426	)		—		—		—

Cash consideration		3,208,310			—		—		—
Directly attributable transaction cost		133,311			—		—		—

Cash paid for capital reorganization		3,341,621			—		—		—

Disposal of a subsidiary


	2016		2017			2018		2018
	NT$000		NT$000			NT$000		US$000
Disposal of a subsidiary		—		2,166,151			—		—
Add: Ending balance of other payables*		—		64,393			—		—
Less: Cash and cash equivalents of discontinued operations		—		(449,331	)		—		—

Cash received from disposal of a subsidiary		—		1,781,213			—		—

According to the Equity Interest Transfer Agreement, the Group accrued the estimated payment to investor based on the operating performance of Unimos Shanghai and as a result, cash received from disposal of discontinued operations amounted to NT$64,393 thousand was returned in 2018.

Reconciliation of liabilities arising from financing activities


						Non-Cash flow
	As of January 1, 2017		Cash flow			Amortization of loans fee		As of December 31, 2017
	NT$000		NT$000			NT$000		NT$000
Long-term bank loans (include the current portion)		10,750,005		(1,124,699	)		16,715		9,642,021
Short-term bank loans		—		969,353			—		969,353
Guarantee deposits		1,404		(33	)		—		1,371

		10,751,409		(155,379	)		16,715		10,612,745


						Non-Cash flow
	As of January 1, 2018		Cash flow			Amortization of loans fee		As of December 31, 2018
	NT$000		NT$000			NT$000		NT$000		US$000
Long-term bank loans (include the current portion)		9,642,021		110,250			37,247		9,789,518		319,815
Short-term bank loans		969,353		(969,353	)		—		—		—
Guarantee deposits		1,371		(279	)		—		1,092		35

		10,612,745		(859,382	)		37,247		9,790,610		319,850

Related party transactions

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Related party transactions

33.

Related party transactions

Parent and ultimate controlling party

On October 31, 2016, the Company’s former parent company, ChipMOS Bermuda, was merged with and into the Company through a share exchange with the latter being the surviving entity and ChipMOS Bermuda being the dissolved entity. After the Merger, the Company has neither a parent company nor an ultimate controlling party. The transactions between the Company and its subsidiaries were eliminated in the accompanying consolidated financial statements and were not disclosed herein. The transactions between the Group and other related parties are as follows.

Names of related parties and relationship


Name	Relationship
Unimos Shanghai		Associate
JMC		Associate

Significant related party transactions

(a)

Subcontracting fee

2016

2017

2018

NT$000

US$000

Unimos Shanghai

—

41,183

(b)

Purchases of materials


	2016		2017		2018		2018
	NT$000		NT$000		NT$000		US$000
JMC		—		130		132,494		4,329
Unimos Shanghai		—		906		3,775		123

		—		1,036		136,269		4,452

Purchases of materials from associates are based on normal commercial terms and conditions. The payment terms of the purchases from associates are 30 to 90 days, which are the same as third party suppliers.

(c)

Disposal of property, plant and equipment


	2017
	Selling price		Gain on disposal
	NT$000		NT$000
Unimos Shanghai		21,982		20,240

There were no disposal of property, plant, and equipment to related parties for the years ended December 31, 2016 and 2018.

(d)

Acquisition of property, plant and equipment


	2018		2018
	NT$000		US$000
Unimos Shanghai		61,904		2,022

There were no acquisition of property, plant, and equipment from related parties for the years ended December 31, 2016 and 2017.

(e)

Acquisition of financial assets

(f)

Patent licensing agreement

In May 2016, the Company and Unimos Shanghai entered into a patent licensing agreement. Under the agreement, Unimos Shanghai paid the Company a licensing fee in the aggregate total of US$2,500 thousand (amended to US$1,000 thousand in January 2017) which was accounted for as receipts in advance and long-term deferred revenue, and recognized royalty income for 10 years from the effective date. In addition, Unimos Shanghai shall pay the Company a running royalty for the foregoing license equivalent to 0.5% of the total revenue from the licensed products. Given that the related production lines of Unimos Shanghai have begun its operations in April 2017, the Company recognized royalty income henceforth. In April 2018, both parties agreed to terminate the agreement after an amicable negotiation, hence all remaining receipts in advance and long-term deferred revenue were recognized as royalty income. The Company recognized receipts in advance and long-term deferred revenue amounted to NT$3,018 thousand and NT$24,898 thousand, respectively, as of December 31, 2017 and royalty income amounted to NT$2,828 thousand for the year then ended. The Company recognized receipts in advance and long-term deferred revenue amounted to nil as of December 31, 2018 and royalty income amounted to NT$30,683 thousand (US$1,002 thousand) for the year then ended.

In October 2011, ChipMOS Bermuda and Unimos Shanghai entered into a patent licensing agreement which has a term of 10 years starting from August 1, 2012. Under the agreement, Unimos Shanghai will pay ChipMOS Bermuda a royalty in the aggregate total of RMB 27,400 thousand, which was accounted as receipts in advance and payable in 40 quarterly installments of RMB 685 thousand. The rights and obligations of this agreement have been transferred to the Company on October 31, 2016. In March 2017, Unimos Shanghai was derecognized from the consolidated financial statements and recorded as “Investment in associates”, therefore, royalty income for the three months ended March 31, 2017 were eliminated on a consolidated basis. The Company recognized receipts in advance amounted to NT$1,039 thousand as of December 31, 2017 and royalty income amounted to NT$9,170 thousand for the year then ended. The Company recognized receipts in advance amounted to NT$1,013 thousand (US$33 thousand) as of December 31, 2018 and royalty income amounted to NT$12,506 thousand (US$409 thousand) for the year then ended.

Key management personnel compensation


	2016		2017		2018		2018
	NT$000		NT$000		NT$000		US$000
Salaries and short-term employee benefits		152,319		188,105		151,095		4,936
Post-employment compensation		3,335		5,622		2,067		68
Share-based payments		109,255		18,736		6,763		221

		264,909		212,463		159,925		5,225

Pledged or mortgaged assets

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Pledged or mortgaged assets

34.

Pledged or mortgaged assets

The Group provided certain assets as collateral mainly for long-term bank loans (Note 24) and leases, which were as follows:


	December 31, 2017		December 31, 2018		December 31, 2018
	NT$000		NT$000		US$000
Non-current financial assets at amortized cost		—		68,388		2,234
Property, plant and equipment, net (Note 16)		7,164,089		9,672,238		315,983
Other non-current financial assets		70,241		—		—

		7,234,330		9,740,626		318,217

Financial risk management and fair values of financial instruments

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Financial risk management and fair values of financial instruments

35.

Financial risk management and fair values of financial instruments

Financial instruments by category


	December 31, 2017		December 31, 2018		December 31, 2018
	NT$000		NT$000		US$000
Financial assets
Financial assets at fair value through profit or loss
Financial assets mandatorily measured at fair value through profit or loss		—		11,471		375
Financial assets at fair value through other comprehensive income
Designation of equity instruments		—		174,357		5,696
Available-for-sale financial assets
Non-current financial assets carried at cost		20,890		—		—
Financial assets at amortized cost/loans and receivables
Cash and cash equivalents		8,035,714		4,642,522		151,667
Financial assets at amortized cost		—		268,271		8,763
Accounts and notes receivable		4,015,734		4,747,288		155,090
Accounts receivable – related parties		11		140		5
Other receivables		56,716		63,037		2,059
Other receivables – related parties		4,534		3,131		102
Refundable deposits		21,342		22,006		719
Other financial assets		70,241		—		—

		12,225,182		9,932,223		324,476


	December 31, 2017		December 31, 2018		December 31, 2018
	NT$000		NT$000		US$000
Financial liabilities
Financial liabilities at amortized cost
Short-term bank loans		969,353		—		—
Accounts payable		687,960		637,271		20,819
Accounts payable – related parties		226		347		11
Payables to contractors and equipment suppliers		713,313		1,516,735		49,550
Other payables		1,980,182		1,678,482		54,835
Other payables – related parties		36		218		7
Long-term bank loans (including current portion)		9,642,021		9,789,518		319,815
Guarantee deposits		1,371		1,092		35

		13,994,462		13,623,663		445,072

Financial risk management

The Group’s risk management objective is to manage the market risk, credit risk and liquidity risk related to its operating activities. The Group identifies, measures and manages the aforementioned risks based on policy and risk appetite.

The Group has established appropriate policies, procedures and internal controls for financial risk management. Before entering into significant financial transactions, due approval process by the Board of Directors must be carried out based on related protocols and internal control procedures. The Group complies with its financial risk management policies at all times.

(a)

Market risk

Market risk is the risk that the fair value or future cash flows of a financial instrument will fluctuate because of changes in market prices. Market risks comprise foreign currency risk, interest rate risk, and other price risk.

Foreign currency risk

The Group’s exposure to the risk of changes in foreign exchange rates relates primarily to the Group’s operating activities (when revenue or expense is denominated in a different currency from the Group’s functional currency) and the Group’s net investments in foreign operations.

The Group applies natural hedges from using accounts receivable and accounts payable denominated in the same currency. However, this natural hedge does not concur with the requirement for hedge accounting. Furthermore, as net investments in foreign operations are for strategic purposes, they are not hedged by the Group.

The Group’s foreign currency exposure gives rise to market risks associated with exchange rate movements against the NT dollar for cash and cash equivalents, accounts receivable, other receivables, bank loans, accounts payable and other payables.

The Group’s businesses involve some non-functional currency operations. The information on the assets and liabilities denominated in foreign currencies whose values would be materially affected by the exchange rate fluctuations is as follows:


	December 31, 2017
	Foreign currency		Exchange rate		Carrying amount (NT$000)
Financial assets
Monetary items
US$000		208,066		29.7600		6,192,044
JPY000		798,254		0.2642		210,899
RMB000		167,484		4.5650		764,564
Financial liabilities
Monetary items
US$000		16,036		29.7600		477,231
JPY000		1,071,432		0.2642		283,072


	December 31, 2018
	Foreign currency		Exchange rate		Carrying amount (NT$000)
Financial assets
Monetary items
US$000		170,270		30.7150		5,229,843
JPY000		177,557		0.2782		49,396
RMB000		8,850		4.4720		39,577
Financial liabilities
Monetary items
US$000		18,230		30.7150		559,934
JPY000		2,436,140		0.2782		677,734

The total exchange gain and loss recognized include realized and unrealized gain and loss arising from significant foreign exchange variation on the monetary items held by the Group for the years ended December 31, 2017 and 2018 amounted to loss of NT$418,970 thousand and gain of NT$93,104 thousand (US$3,041 thousand), respectively.

The following table details the Group’s exposure at the end of the reporting period to currency risk arising from recognized monetary assets or liabilities denominated in a currency other than the functional currency of the entity to which they relate.


	2017
	Change in exchange rate		Effect on profit (NT$000)		Effect on other comprehensive income (NT$000)
Financial assets
US$000		5%		309,602		—
JPY000		5%		10,545		—
RMB000		5%		38,228		—
Financial liabilities
US$000		5%		23,862		—
JPY000		5%		14,154		—


	2018
	Change in exchange rate		Effect on profit (NT$000)		Effect on other comprehensive income (NT$000)
Financial assets
US$000		5%		261,492		—
JPY000		5%		2,470		—
RMB000		5%		1,979		—
Financial liabilities
US$000		5%		27,997		—
JPY000		5%		33,887		—

ii)

Price risk

The Group’s financial instruments, which are exposed to price risk, are the financial assets at fair value through profit or loss and financial assets at fair value through other comprehensive income. To manage its price risk arising from investments in financial instruments, the Group diversifies its portfolio. Diversification of the portfolio is in accordance with the limits set by the Group.

The Group’s investments in financial instruments comprise foreign unlisted stocks and partnerships. The prices of financial instruments would change due to different valuation models and assumptions used. Analysis related to the effect on profit or other comprehensive income if these assumptions change is provided in Note 35 c) (g).

iii)

Interest rate risk on cash flow and fair value

Interest rate risk is the risk that the fair value or future cash flows of a financial instrument will fluctuate because of changes in market interest rates. The Group’s exposure to the risk of changes in market interest rates relates primarily to the Group’s bank loans with floating interest rates.

The Group manages its interest rate risk by having a balanced portfolio of fixed and variable rate bank loans.

At December 31, 2018, it is estimated that a general increase or decrease of 100 basis points (1%) in interest rates, with all other variables held constant, would decrease or increase the Group’s profit by approximately NT$98,220 thousand (US$3,209 thousand) (2017: NT$106,447 thousand).

(b)

Credit risk

Credit risk is the risk that a counterparty will not meet its obligations under a financial instrument or customer contract, leading to a financial loss. The Group is exposed to credit risk from its operating activities (primarily accounts and other receivables) and from its financing activities (primarily deposits with banks and financial instruments).

Each business unit performs ongoing credit evaluation of the debtors’ financial condition according to the Group’s established policy, procedures and control relating to customer credit risk management. The Group maintains an account for loss allowance based upon the available facts and circumstances, historical collection and write-off experiences of all trade and other receivables which consequently minimizes the Group’s exposure to bad debts.

Credit risk from balances with banks and financial institutions is managed by the Group’s finance unit in accordance with the Group’s policy. Bank balances are held with financial institutions of good standing. The Group’s exposure to credit risk arising from the default of counter-parties is limited to the carrying amount of these instruments.

The Group adopts the assumptions under IFRS 9 and the default is deemed to have occurred when the contract payments are past due over 90 days.

The Group categorized contract assets, accounts receivable and other receivables by characteristics of credit risk and applied the simplified approach using loss rate methodology to estimate expected credit loss.

The Group used the forecastability of business monitoring indicators to adjust historical and timely information to assess the default possibility of contract assets, accounts receivable and other receivables. On December 31, 2018, the loss rate methodology is as follows:


	December 31, 2018
	Contract assets			Accounts receivable (including related parties)			Other receivables (including related parties)
	NT$000			NT$000			NT$000
Expected loss rate		0.045%			0.045%			0.045%
Total carrying amount		299,970			4,747,974			66,181
Loss allowance		(135	)		(2,141	)		(13	)

Under the simplified approach, movements in relation to loss allowance for contract assets, accounts receivable, and other receivables are as follows:


	2018
	Contract assets			Accounts receivable (including related parties)			Other receivables (including related parties)
	NT$000			NT$000			NT$000
January 1_ IAS 39		—			—			—
Adjustments for applying new standards		(115	)		(1,819	)		(7	)

January 1_IFRS 9		(115	)		(1,819	)		(7	)
Provision for impairment loss		(20	)		(322	)		(7	)
Reversal of impairment loss		—			—			1

December 31		(135	)		(2,141	)		(13	)

For investments in financial assets at amortized cost, the credit rating levels are presented below:

December 31, 2018

By lifetime

12 months

Increase in
credit risk

Impairment
of credit

Total

NT$000

Financial assets at amortized cost Bank deposits (Note)

268,271

—

268,271

Note: Time deposits with contract period over three months and restricted bank deposits.

Information related to credit risk for the year ended December 31, 2017 is provided in Note 41.

(c)

Liquidity risk

Liquidity risk is the risk that the Group will encounter difficulty in raising funds to meet commitments associated with financial instruments. The Group monitors and maintains adequate cash and banking facilities to finance the Group’s operations. See Notes 24 and 29 about the unused credit lines of the Group.

The maturity profile of the Group’s non-derivative financial liabilities as of December 31, 2017 and 2018 based on the contracted undiscounted payments is as follows:


	December 31, 2017
	Within 1 year		1 to 5 years		Over 5 years		Total
	NT$000		NT$000		NT$000		NT$000
Short-term bank loans		971,813		—		—		971,813
Long-term bank loans (including current portion)		2,321,459		7,740,267		—		10,061,726
Accounts payable and payables to contractors and equipment suppliers (including related parties)		1,401,499		—		—		1,401,499
Other payables (including related parties)		1,980,218		—		—		1,980,218
Lease obligations payable		12,266		18,266		—		30,532
Guarantee deposits		—		—		1,371		1,371

		6,687,255		7,758,533		1,371		14,447,159


	December 31, 2018
	Within 1 year		1 to 5 years		Over 5 years		Total		Total
	NT$000		NT$000		NT$000		NT$000		US$000
Long-term bank loans (including current portion)		927,243		9,549,327		—		10,476,570		342,260
Accounts payable and payables to contractors and equipment suppliers (including related parties)		2,154,353		—		—		2,154,353		70,380
Other payables (including related parties)		1,678,700		—		—		1,678,700		54,842
Lease obligations payable		18,000		—		—		18,000		588
Guarantee deposits		—		—		1,092		1,092		35

		4,778,296		9,549,327		1,092		14,328,715		468,105

Fair value information

(a)

The different levels of inputs used in valuation techniques to measure fair value of financial and non-financial instruments are provided in Note 2 bb).

(b)

The carrying amounts of cash and cash equivalents, financial assets at amortized cost, contract assets, notes receivable, accounts receivable, other receivables, refundable deposits, bank loans, contract liabilities, accounts payable, payables to contractors and equipment suppliers, other payables, lease obligations payable and guarantee deposits are approximate to their fair values.

(c)

The related information of financial and non-financial instruments measured at fair value by level on the basis of the nature, characteristics and risks of the assets and liabilities are as follows:

(i)

The related information of natures of the assets and liabilities is as follows:

December 31, 2018

Level 1

Level 2

Level 3

Total

NT$000

US$000

Assets

Recurring fair value measurements

Financial assets at fair value through profit or loss

- Foreign partnership interests

—

11,471

375

Financial assets at fair value through other comprehensive income

- Foreign unlisted stocks

—

174,357

5,696

—

185,828

6,071

There were no financial and non-financial instruments measured at fair value as of December 31, 2017.

(ii)

The methods and assumptions the Group used to measure fair value are as follows:

The fair value of the Group’s financial instruments is measured by using valuation techniques or by reference to counterparty quotes. The fair value of financial instruments measured by using valuation techniques can be referred to current fair value of instruments with similar terms and characteristics in substance, discounted cash flow method or other valuation methods, including calculated by applying model using market information available at the consolidated statement of financial position date.

The Group’s financial assets at fair value through profit or loss is measured by using the discounted cash flow method, which derives present value estimates by discounting expected future operating effectiveness and free cash flows projections.

The Group’s financial assets at fair value through other comprehensive income is measured by the comparable company valuation (EV/EBITDA ratio and P/B ratio).

The Group takes into account adjustments for credit risks to measure the fair value of financial and non-financial instruments to reflect credit risk of the counterparty and the Group’s credit quality.

(d)

The following table shows the movements of Level 3 for the year ended December 31, 2018:


	December 31, 2018
	Debt instruments				Equity instruments
	NT$000		US$000		NT$000		US$000
January 1		—		—		—		—
Effects on initial application of IFRS 9		11,433		374		89,335		2,918
Gains or losses recognized in profit or loss
Recorded as non-operating income (expenses)		38		1		—		—
Gains or losses recognized in other comprehensive income
Recorded as unrealized gains on valuation of financial assets at fair value through other comprehensive income		—		—		85,022		2,778

December 31		11,471		375		174,357		5,696

There were no Level 3 movements for the year ended December 31, 2017.

(e)

The Group performs the fair value measurements being categorized within Level 3 with assistance from specialist. Such assessment is to ensure the valuation results are reasonable by applying independent information to make results close to current market conditions, confirming the resource of information is independent, reliable and in line with other resources and represented as the exercisable price, and frequently calibrating valuation model, performing back-testing, updating inputs used in the valuation model and making any other necessary adjustments to the fair value.

(f)

The following is the qualitative information and sensitivity analysis of changes in significant unobservable inputs under valuation model used in Level 3 fair value measurement:

Fair value as of
December 31,
2018
(NT$000)

Valuation
technique

Significant

unobservable
input

Range
(weighted
average
method)

Relationship of inputs

to fair value

Non-derivative debt instrument:

Foreign partnership interests

11,471

Discounted cash flow

Discount rate

0.35%

The lower the discount rate, the higher the fair value

Non-derivative equity instrument:

Foreign unlisted stocks

174,357

Comparable companies

Price to book ratio multiple

1.19

The higher the multiple, the higher the fair value

Enterprise value to EBITDA multiple

7.69

The higher the multiple, the higher the fair value

Discount for lack of marketability

15.80%

The higher the discount for lack of marketability, the lower the fair value

(g)

The Group has carefully assessed the valuation models and assumptions used to measure fair value. However, use of different valuation models or assumptions may result in different measurement. The following is the effect of profit or loss or of other comprehensive income from financial assets categorized within Level 3 if the inputs used to valuation models have changed:


			December 31, 2018
			Recognized in profit or loss				Recognized in other comprehensive income
	Input	Change	Favorable change		Unfavorable change		Favorable change		Unfavorable change
			NT$000		NT$000		NT$000		NT$000
Financial assets
Foreign partnership interests	Discount rate	Note		—		—		—		—
Foreign unlisted stocks	Price to book ratio multiple	± 1%		—		—		69		68
	Enterprise to EBITDA multiple	± 1%		—		—		1,563		1,512
	Discount for lack of marketability	± 1%		—		—		2,093		2,050

				—		—		3,725		3,630

Note: Based on the Group’s assessment, change in input would not have significant impact on profit or loss or other comprehensive income.

Share-based payments

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Share-based payments

36.

Share-based payments

Restricted Shares

On November 12, 2014, the Board of Directors of the Company approved 2014 Restricted Stock Award Agreement which has 17,300 thousand restricted shares available for issuance. The par value and granting price of the restricted shares were NT$10 and zero, respectively. The issuance of the restricted shares was approved by the Special General Meeting of the Shareholders of the Company on December 30, 2014 and approved by the Financial Supervisory Commission ROC on June 30, 2015.

On July 14, 2015 and April 18, 2016, the Board of Directors of the Company approved to set July 21, 2015 and May 10, 2016 as the Record Date of the issuance of 15,752 thousand and 1,548 thousand restricted shares.

When the employees of ChipMOS Taiwan accomplished the following years of service and performance conditions, the received restricted shares will be vested based on the vesting ratio.


	The 1^st year	The 2^nd year	The 3^rd year
Years of service following the receipt of restricted shares	Continuous service for one year	Continuous service for two years	Continuous service for three years
Grade of performance appraisal	>=B+	>=B+	>=B+
Compliance of terms agreed by the staff and the Company	No violation	No violation	No violation
Vesting ratio of numbers of restricted shares received	30%	30%	40%

The restricted shares issued by the Company cannot be transferred during the vesting period, but voting right and dividend right are not restricted. Employees are required to return the shares but not required to return the dividends received if they resign during the vesting period. When the employees accomplish the years of service and performance conditions, the received restricted shares will be vested based on the vesting ratio.

During 2017 and 2018, the Group recognized NT$123,021 thousand and NT$41,043 thousand (US$1,341 thousand), respectively, compensation expenses in respect of the transactions of share-based payments.

Capital management

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Capital management

37.

Capital management

The Group manages its capital to ensure that entities in the Group will be able to continue as a going concern while maximizing the return to shareholders through the optimization of the balance between debt and equity.

The Group reviews the capital structure on an ongoing basis. As part of this review, the directors consider the cost of capital and the risks associated with each class of capital. The Group will balance its overall capital structure through the payment of dividends, new share issues and the issue of new debt or the repayment of existing debt.

The Group’s overall strategy remains unchanged from 2017.

The Group monitors capital using the liabilities to assets ratio, the percentages of which as of December 31, 2017 and 2018 were as follows:

December 31, 2017

December 31, 2018

NT$000

US$000

Total liabilities

15,138,993

15,112,545

493,713

Total assets

33,259,942

33,133,718

1,082,448

Liabilities to assets ratio

45.52%

45.61%

Financial Statements Schedule: Valuation and Qualifying Accounts

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Financial Statements Schedule: Valuation and Qualifying Accounts

40.

Financial Statements Schedule: Valuation and Qualifying Accounts


	January 1		Additions charged to expense		Deduction / Write-offs			Exchange difference on translations of foreign financial statement			Non-current assets held for sale			December 31
	NT$000		NT$000		NT$000			NT$000			NT$000			NT$000
Year of 2016 :

Allowance for impairment of property, plant and equipment		1,994,715		8,198		(45,319	)		(118,046	)		(1,480,278	)		359,270

Allowance for impairment of obsolescence and decline in market value of inventories		95,036		66,894		—			(557	)		(6,532	)		154,841

Allowance for impairment of accounts receivable		—		87		—			—			—			87

Year of 2017 :

Allowance for impairment of property, plant and equipment		359,270		956		(39,771	)		—			—			320,455

Allowance for impairment of obsolescence and decline in market value of inventories		154,841		—		(101,127	)		—			—			53,714

Allowance for impairment of accounts receivable		87		—		(87	)		—			—			—

Year of 2018 :

Allowance for impairment of property, plant and equipment		320,455		—		(2,862	)		—			—			317,593

Allowance for impairment of obsolescence and decline in market value of inventories		53,714		—		(17,557	)		—			—			36,157

Loss allowance for accounts receivable*		1,819		322		—			—			—			2,141

The Group initially applied IFRS 9 on January 1, 2018, and recorded loss allowance amounted to NT$1,819 thousand based on expected credit loss. Please refer to Note 41 for the details of significant effects as of January 1, 2018 on applying the aforementioned new standard.

Effects on initial application of IFRS 9 and information for the years ended December 31, 2016 and 2017 in conformity with IAS 39

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Effects on initial application of IFRS 9 and information for the years ended December 31, 2016 and 2017 in conformity with IAS 39

41.

Effects on initial application of IFRS 9 and information for the years ended December 31, 2016 and 2017 in conformity with IAS 39

Summaries of adopting significant accounting policies for the years ended December 31, 2016 and 2017:

Investments and other financial assets

Initial recognition and measurement

The Group’s financial assets are classified, at initial recognition, into financial assets at fair value through profit or loss (“FVTPL”), loans and receivables and available-for-sale financial investments. When financial assets are recognized initially, they are measured at fair value plus transaction costs that are attributable to the acquisition of the financial assets.

All regular way purchases or sales of financial assets are recognized on the settlement date, that is, the date that the Group completes the purchase or sell of the asset. Regular way purchases or sales are purchases or sales of financial assets that require delivery of assets within the time frame established by regulation or convention in the marketplace.

Effective

interest method

The effective interest method is a method of calculating the amortized cost of loans and receivables and a debt instrument and of allocating interest income over the relevant period. The effective interest rate is the rate that exactly discounts estimated future cash receipts (including all fees on points paid or received that form an integral part of the effective interest rate, transaction costs and other premiums or discounts) through the expected life of the debt instrument, or, where appropriate, a shorter period.

Income is recognized on an effective interest basis for debt instruments.

Subsequent

measurement

The subsequent measurement of financial assets depends on their classification as follows:

Financial assets at fair value through profit or loss

Financial assets at FVTPL include financial assets held for trading and those designated as at FVTPL upon initial recognition.

A financial asset is classified as held for trading, mainly for cash management purpose as part of operating activities, if it has been acquired principally for the purpose of selling in the near future; or it is a part of an identified portfolio of financial instruments that the Group manages together and has a recent actual pattern of short-term profit-taking; or it is a derivative that is not designated and effective as a hedging instrument.

A financial asset other than a financial asset held for trading may be designated as at FVTPL upon initial recognition if:

•

such designation eliminates or significantly reduces a measurement or recognition inconsistency that would otherwise arise; or

•

the financial asset forms part of a group of financial assets or financial liabilities or both, which is managed and its performance is evaluated on fair value basis, in accordance with the Group’s documented risk management or investment strategy, and information about the grouping is provided internally on that basis; or

•

it forms part of a contract containing one or more embedded derivatives, and IAS 39 “Financial Instruments: Recognition and Measurement” permits the entire combined contract (asset or liability) to be designated as at FVTPL.

Loans and receivables

Loans and receivables are non-derivative financial assets with fixed or determinable payments that are not quoted in an active market. At the end of each reporting period, subsequent to initial recognition, loans and receivables (including accounts and notes receivables, other receivables, refundable deposits, short-term deposits and cash and cash equivalents) are carried at amortized cost using the effective interest method, less any identified impairment losses.

Available-for-sale financial investments

Available-for-sale financial investments are non-derivative financial assets in unlisted equity investments. Equity investments classified as available for sale are those which are neither classified as held for trading nor designated as at fair value through profit or loss.

When the fair value of unlisted equity investments cannot be reliably measured because (a) the variability in the range of reasonable fair value estimates is significant for that investment or (b) the probabilities of the various estimates within the range cannot be reasonably assessed and used in estimating fair value, such investments are stated at cost less any impairment losses.

The Group evaluates whether the ability and intention to sell its available-for-sale financial investments in the near term are still appropriate. When, in rare circumstances, the Group is unable to trade these financial assets due to inactive markets, the Group may elect to reclassify these financial assets if management has the ability and intention to hold the assets for the foreseeable future or until maturity.

Impairment of financial assets

The Group assesses at the end of each reporting period whether there is objective evidence that a financial asset or a group of financial assets is impaired. An impairment exists if one or more events that occurred after the initial recognition of the asset have an impact on the estimated future cash flows of the financial asset or the group of financial assets that can be reliably estimated. Evidence of impairment may include indications that a debtor or a group of debtors is experiencing significant financial difficulty, default or delinquency in interest or principal payments, the probability that they will enter bankruptcy or other financial reorganization and observable data indicating that there is a measurable decrease in the estimated future cash flows, such as changes in arrears or economic conditions that correlate with defaults.

Financial assets carried at amortized cost

For financial assets carried at amortized cost, the Group first assesses whether impairment exists individually for financial assets that are individually significant, or collectively for financial assets that are not individually significant. If the Group determines that no objective evidence of impairment exists for an individually assessed financial asset, whether significant or not, it includes the asset in a group of financial assets with similar credit risk characteristics and collectively assesses them for impairment. Assets that are individually assessed for impairment and for which an impairment loss is, or continues to be, recognized are not included in a collective assessment of impairment.

The amount of any impairment loss identified is measured as the difference between the asset’s carrying amount and the present value of estimated future cash flows (excluding future credit losses that have not yet been incurred). The present value of the estimated future cash flows is discounted at the financial asset’s original effective interest rate (i.e., the effective interest rate computed at initial recognition). The carrying amount of the asset is reduced through the use of an allowance account and the loss is recognized in the consolidated statements of comprehensive income. Interest income continues to be accrued on the reduced carrying amount and is accrued using the rate of interest used to discount the future cash flows for the purpose of measuring the impairment loss. Loans and receivables together with any associated allowance are written off when there is no realistic prospect of future recovery and all collateral has been realized or has been transferred to the Group.

If, in a subsequent period, the amount of the estimated impairment loss increases or decreases because of an event occurring after the impairment was recognized, the previously recognized impairment loss is increased or reduced by adjusting the allowance account. If a write-off is later recovered, the recovery is credited to other expenses in the consolidated statements of comprehensive income.

Available-for-sale financial assets

The amount of the impairment loss is measured as the difference between the asset’s acquisition cost (less any principal repayment and amortization) and current fair value, less any impairment loss on that financial asset previously recognized in profit or loss, and is reclassified from “other comprehensive income” to “profit or loss”. If, in a subsequent period, the fair value of an investment in a debt instrument increases, and the increase can be related objectively to an event occurring after the impairment loss was recognized, then such impairment loss is reversed through profit or loss. Impairment loss of an investment in an equity instrument recognized in profit or loss shall not be reversed through profit or loss. Impairment loss is recognized and reversed by adjusting the carrying amount of the asset directly.

The Group initially applied IFRS 9 on January 1, 2018, and recorded loss allowance based on expected credit loss. The impact was contract assets decreased by NT$115 thousand (US$4 thousand), accounts receivable decreased by NT$1,819 thousand (US$59 thousand), other receivables decreased by NT$5 thousand (US$163), other receivables – related parties decreased by NT$2 thousand (US$65), retained earnings decreased by NT$1,940 thousand (US$63 thousand) and deferred tax assets increased by NT$1 thousand (US$33).

The carrying amount of financial assets transferred from December 31, 2017 under IAS 39 to January 1, 2018 under IFRS 9 is reconciled as follows:


																	Effects
	Note		Measured at cost			Measured at fair value through profit or loss		Measured at fair value through other comprehensive income		Other financial assets			Measured at amortized cost		Total		Retained earnings		Other equity interest
			NT$000			NT$000		NT$000		NT$000			NT$000		NT$000		NT$000		NT$000
IAS 39				20,890			—		—		70,241			—		91,131		—		—
Transferred into and measured at fair value through profit or loss		(c)		(10,940	)		10,940		—		—			—		—		—		—
Transferred into and measured at fair value through other comprehensive income		(b)		(9,950	)		—		9,950		—			—		—		—		—
Transfer into and measured at amortized cost		(a)		—			—		—		(70,241	)		70,241		—		—		—
Fair value adjustment		(b)(c)		—			493		50,801		—			—		51,294		493		79,385
Impairment loss adjustment		(b)		—			—		28,584		—			—		28,584		28,584		(28,584	)
Income tax adjustment		(b)		—			—		—		—			—		—		—		(8,636	)

IFRS 9				—			11,433		89,335		—			70,241		171,009		29,077		42,165

(a)

The Group’s restricted bank deposits that failed to meet the definition of cash and cash equivalents amounted to NT$70,241 thousand (US$2,295 thousand) were classified as “Other financial assets” under IAS 39. Since the assets’ cash flows represent solely payments of principal and interest, the restricted bank deposits were reclassified as “Financial assets at amortized cost” amounted to NT$70,241 thousand (US$2,295 thousand) on initial application of IFRS 9.

(b)

Given the Group’s available-for-sale financial assets amounted to NT$9,950 thousand (US$325 thousand) under IAS 39 were not held for the purpose of trading, it was elected to classify as “Financial assets at fair value through other comprehensive income” and increased by NT$89,335 thousand (US$2,918 thousand) on initial application of IFRS 9. Accompanying retained earnings, other equity interest and deferred tax liabilities were increased by NT$28,584 thousand (US$934 thousand), NT$42,165 thousand (US$1,377 thousand) and NT$8,636 thousand (US$282 thousand), respectively.

(c)

The Group’s available-for-sale financial assets amounted to NT$10,940 thousand (US$357 thousand) under IAS 39 were classified as “Financial assets at fair value through profit or loss” and increased by NT$11,433 thousand (US$374 thousand) in compliance with IFRS 9. Accompanying retained earnings were increased by NT$493 thousand (US$16 thousand).

The significant account as of December 31, 2017 is as follows:

Available-for-sale financial assets


	December 31, 2017
	NT$000
Unlisted equity investments, at cost		49,474
Less: Allowance for impairment losses		(28,584	)

		20,890

Due to the operation loss and accumulated deficit of VIGOUR TECHNOLOGY Corporation (“VIGOUR”), the Company has recognized full impairment loss of its investments on VIGOUR amounted to NT$41,336 thousand in prior years. Based on the Company’s assessment, considering VIGOUR is currently in liquidation process and no residual assets are expected to be available for distributions, the carrying amount of investments and accumulated impairment losses were reclassified to “Other receivables” in the fourth quarter of 2017.

As of December 31, 2017, no available-for-sale financial assets were pledged.

Credit risk information as of December 31, 2017 is as follows:

(a)

(b)

Each business unit performs ongoing credit evaluation of the debtors’ financial condition according to the Group’s established policy, procedures and control relating to customer credit risk management. The Group maintains an account for allowance for doubtful receivables based upon the available facts and circumstances, historical collection and write-off experiences of all trade and other receivables which consequently minimizes the Group’s exposure to bad debts.

(c)

(d)

The aging of accounts receivable which are past due but not impaired is as follows:


	December 31, 2017
	NT$000
£ 1 month		10,482
1-2 months		477
2-3 months		426
3-4 months		1,431
> 4 months		3,056

		15,872

(e)

The movements in allowance for impairment of accounts and other receivables during the year is as follows:


	Accounts receivable			Other receivables
	NT$000			NT$000
January 1, 2017		87			—
Reversal of allowance for impairment losses		(87	)		—

December 31, 2017		—			—

Receivables that were neither past due nor impaired relate to a large number of diversified customers for whom there was no recent history of default.

Receivables that were past due but not impaired relate to a number of independent customers that have a good track record with the Group. Based on past experience, the management of the Company are of the opinion that no provision for impairment is necessary in respect of these balances as there has not been a significant change in credit quality and the balances are still considered fully recoverable.

The individually impaired receivables related to customers that were in financial difficulties or other factors, e.g. the customers were in default or delinquency in interest or principal payments and only a portion of the receivables is expected to be recovered.

The Group’s accounts receivable that were neither past due nor impaired were fully performed in line with the credit standards prescribed based on counterparties’ industrial characteristics, scale of business and profitability.

(f)

As of December 31, 2017, no accounts and notes and other receivables were pledged.

Effects on initial application of IFRS 15 and information for the years ended December 31, 2016 and 2017 in conformity with IAS 18

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Effects on initial application of IFRS 15 and information for the years ended December 31, 2016 and 2017 in conformity with IAS 18

42.

Effects on initial application of IFRS 15 and information for the years ended December 31, 2016 and 2017 in conformity with IAS 18

The significant accounting policies applied on revenue recognition for the years ended December 31, 2016 and 2017 are set out below:

Revenue recognition

Revenue is recognized to the extent that it is probable that the economic benefits arising in the course of business will flow to the Group and the revenue can be reliably measured, regardless of when the payment is being made. Revenue is measured at the fair value of the consideration received or receivable, taking into account contractually defined terms of payment and excluding taxes or duty.

The Group engaged in the research, development, manufacturing and sale of high-integration and high-precision integrated circuits and related assembly and testing services. The criteria that the Group uses to determine when to recognize revenue are: (a) the Group has transferred to the buyer the significant risks and rewards of ownership of the goods; (b) the Group retains neither continuing managerial involvement to the degree usually associated with ownership nor effective control over the goods sold; (c) the amount of revenue can be measured reliably; (d) it is probable that the economic benefits associated with the transaction will flow to the Group ; (e) the stage of completion of the transaction at the end of the reporting period can be measured reliably, and (f) the costs incurred for the transaction and the costs to complete the transaction can be measured reliably.

The Group does not take ownership of: (1) bare semiconductor wafers received from customers that are assembled into finished semiconductors, and (2) assembled semiconductors received from the customers that it tests. The title and risk of loss remains with the customer for those bare semiconductors and/or assembled semiconductors. Accordingly, the customer-supplied semiconductor materials are not included in the consolidated financial statements.

The Group does not provide warranties to customers except in cases of defects in the assembly services provided and deficiencies in testing services provided. An appropriate sales allowance is recognized in the period during which the sale is recognized, and is estimated based on historical experience.

The revenue recognized by using above accounting policies for the year ended December 31, 2017 are provided in Note 4.

The impact and description on consolidated statement of financial position and statement of comprehensive income if the Group continues adopting above accounting policies as of and for the year ended December 31, 2018 are as follows:


			December 31, 2018
Consolidated statement of financial position items	Description		Balance under IFRS 15		Balance under previous accounting policies		Impact on accounting policy change
			NT$000		NT$000		NT$000
Contract assets		(d)(f)(g)		299,835		—		299,835
Inventories		(e)		1,778,835		2,016,106		(237,271	)
Deferred tax assets		(h)		226,716		226,635		81
Contract liabilities		(i)		1,432		—		1,432
Receipts in advance		(i)		1,013		2,445		(1,432	)
Current provisions		(j)		29,352		61,979		(32,627	)
Current refund liabilities		(j)		32,627		—		32,627
Retained earnings				3,602,663		3,540,018		62,645


			2018
Consolidated statement of comprehensive income items	Description		Balance under IFRS 15			Balance under previous accounting policies			Impact on accounting policy change
			NT$000			NT$000			NT$000
Revenue		(a)(d)		18,480,027			18,434,763			45,264
Cost of revenue		(a)(e)		(15,050,032	)		(15,021,266	)		(28,766	)
Operating expenses		(f)		(1,477,788	)		(1,477,653	)		(135	)
Other non-operating income (expenses), net		(g)		173,070			173,476			(406	)
Income tax expense		(c)(h)		(456,618	)		(465,392	)		8,774
Profit for the year				1,325,824			1,301,093			24,731

Earnings per share (in dollars)
Basic			NT$	1.65		NT$	1.62		NT$	0.03
Diluted			NT$	1.63		NT$	1.60		NT$	0.03

Explanation on the adjustments:

Impact on January 1, 2018

(a)

Revenue recognition of customized products

The Group provides high-integration and high-precision integrated circuits and related assembly and testing services based on the specifications as required by the customers. The revenue is recognized when the significant risks and rewards are transferred to customers under previous accounting policies, and the timing of recognition usually occurred upon service completion. Under IFRS 15, considering that the Group provides assembly and testing service to create or enhance a highly customized product and the customer controls the asset as it is created or enhanced, the revenue will be recognized based on the progress towards completion. As a result, retained earnings increased by NT$46,607 thousand (US$1,523 thousand), inventories decreased by NT$208,505 thousand (US$6,812 thousand) and contract assets increased by NT$255,112 thousand (US$8,334 thousand).

(b)

Presentation of refund liabilities

By adopting IFRS 15, the Group’s provision for sales allowance amounted to NT$70,156 thousand (US$2,292 thousand) is presented as current refund liabilities from January 1, 2018, which was previously presented as current provisions.

(c)

Recognition of deferred tax

When initially adopting IFRS 15, the Group recognized adjustments in the statement of financial position which resulted to temporary differences. Accordingly, as of January 1, 2018, deferred tax assets decreased by NT$626 thousand (US$20 thousand), deferred tax liabilities increased by NT$8,067 thousand (US$264 thousand) and retained earnings decreased by NT$8,693 thousand (US$284 thousand).

Impact on December 31, 2018

(d)

Contract assets and revenue recognition

Under IFRS 15, the Group provides assembly and testing service to create or enhance a highly customized product and the customer controls the asset as it is created or enhanced, the revenue will be recognized based on the progress towards completion. As a result, contract assets and revenue increased by NT$300,376 thousand (US$9,813 thousand) as of December 31, 2018.

(e)

Transfer inventory to cost of revenue

Under IFRS 15, when revenue is recognized based on the progress towards completion, work in process and finished goods in ending inventories should be transferred to cost of revenue at the end of the reporting period. As a result, inventories decreased and cost of revenue increased by NT$237,271 thousand (US$7,751 thousand) as of December 31, 2018.

(f)

Expected credit loss recognition

Under IFRS 15, when contract assets and revenue are recognized based on the progress towards completion, loss allowance is recognized based on the expected credit loss model. As a result, expected credit loss increased and contract assets decreased by NT$135 thousand (US$4 thousand) for the year ended December 31, 2018.

(g)

Foreign exchange

Under IFRS 15, when contract assets and revenue are recognized based on the progress towards completion, foreign exchange loss is also recognized using the exchange rates prevailing at the statement of financial position date. As a result, foreign exchange loss increased and contract assets decreased by NT$406 thousand (US$13 thousand) for the year ended December 31, 2018.

(h)

Recognition of deferred tax

In summary, foreign exchange loss recognized would result to a temporary difference. Accordingly, deferred tax assets increased and income tax expense decreased by NT$81 thousand (US$3 thousand) for the year ended December 31, 2018.

(i)

Presentation of contract liabilities

By adopting IFRS 15, advance payments amounted to NT$1,432 thousand (US$47 thousand) in certain assembly and testing service contracts were presented as contract liabilities as of December 31, 2018, which were previously presented as receipts in advance.

(j)

Presentation of refund liabilities

By adopting IFRS 15, the Group’s provision for sales allowance amounted to NT$32,627 thousand (US$1,066 thousand) was presented as current refund liabilities as of December 31, 2018, which was previously presented as current provisions.

Basis of preparation of financial statements and principal accounting policies (Policies)

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Basis of preparation

Basis of preparation

The consolidated financial statements have been prepared on a historical cost basis, except for the following items:

(a)

Financial assets at fair value through profit or loss (including derivative instruments).

(b)

Financial assets at fair value through other comprehensive income.

(c)

Defined benefit liabilities were recognized based on the net amount of pension fund assets less the present value of benefit obligation.

These consolidated financial statements are presented in New Taiwan dollars (“NT$”), which is the Company’s functional currency.

New and amended standards adopted by the group

b)	*New and amended standards adopted by the group*


New Standards, Interpretations and Amendments		Effective date issued by IASB
IFRS 9, “Financial Instruments”		January 1, 2018
IFRS 15, “Revenue from Contracts with Customers”		January 1, 2018

(a)

IFRS 9 “Financial Instruments”

(i)

(ii)

(iii)

(iv)

(b)

IFRS 15 “Revenue from Contracts with Customers” and amendments

(i)

(ii)

Step

1: Identify the contract(s) with a customer.

Step

2: Identify the performance obligations in the contract(s).

Step

3: Determine the transaction price.

Step

4: Allocate the transaction price to the performance obligations in the contract(s).

Step

5: Recognize revenue when (or as) the entity satisfies the performance obligation.

(iii)

New and revised International Financial Reporting Standards not yet adopted

c)	*New and revised International Financial Reporting Standards not yet adopted*


New Standards, Interpretations and Amendments		Effective date issued by IASB
IFRS 16, “Leases”		January 1, 2019

In applying IFRS 16 for the first time, the Group has used the following practical expedients permitted by the standard:

•

the use of a single discount rate to a portfolio of leases with reasonably similar characteristics,

•

the accounting for operating leases with a remaining lease term of less than 12 months as of January 1, 2019 as short-term leases,

•

the use of hindsight in determining the lease term where the contract contains options to extend or terminate the lease.

Other Amendments to IFRSs not listed above are not expected to have a material impact on the entity in the current or future reporting periods and on foreseeable future transactions.

Basis of consolidation

Basis of consolidation

Subsidiaries included in the consolidated financial statements:

Percentage of
Ownership (%)

December 31,

Name of investor

Name of investee

Main businesses

Location

2017

2018

The Company

ChipMOS U.S.A., Inc. (“ChipMOS USA”)

Research, development and marketing of semiconductors, circuits, and electronic related products

San Jose, USA

100

The Company

ChipMOS BVI

Holding company

British Virgin Islands

100

Significant judgments and estimates

Significant judgments and estimates

Management has considered the development, selection and disclosure of the Group’s critical accounting policies and estimates.

Judgments

Provisions for deficiency compensation

Estimates and assumptions

Revenue recognition

Refund liabilities

Causes and effects of accounting change


	2016			2017			2018			2019
	NT$000			NT$000			NT$000			NT$000
Decrease in depreciation expenses		(119,737	)		(605,259	)		(391,669	)		(164,863	)

Property, plant and equipment and depreciation

Property, plant and equipment and depreciation

Property, plant and equipment are stated at cost, less provision for depreciation and impairment losses, if any.

Depreciation is provided on the straight-line method, based on the estimated useful life of the individual assets, as follows:


Buildings		5 to 51 years
Machinery and equipment		2 to 8 years
Tools		2 to 4 years
Other equipment		2 to 6 years

Impairment of non-financial assets

Impairment of non-financial assets

Inventories

Inventories

Net realizable value is the estimated selling price in the ordinary course of business less the estimated costs of completion and the estimated costs necessary to make the sale.

Non-current assets held for sale

Non-current assets held for sale

Investments and other financial assets

Investments and other financial assets

Classification

From 1 January, 2018, the group classifies its financial assets in the following measurement categories:

(a)

those to be measured subsequently at fair value (either through other comprehensive income (“OCI”) or through profit or loss), and

(b)

those to be measured at amortized cost.

The classification depends on the entity’s business model for managing the financial assets and the contractual terms of the cash flows.

Recognition and derecognition

Measurement

Debt instruments

Equity instruments

Impairment

Investments in associates

Investments in associates

(a)

(b)

Financial liabilities

Financial liabilities

Initial recognition and measurement

All financial liabilities are recognized initially at fair value and, in the case of loans and borrowings, net of directly attributable transaction costs.

The Group’s financial liabilities include bank loans, accounts payable and other monetary liabilities.

Subsequent measurement

The subsequent measurement of financial liabilities depends on their classification as follows:

Loans and borrowings

Notes and accounts payable

Derecognition of financial liabilities

Derecognition of financial liabilities

Dividends

Dividends

Dividends are recommended by the Board of Directors to the Shareholders’ approval pursuant to the Company’s Article of Incorporation.

Operating lease charges

Operating lease charges

Treasury stock

Treasury stock

Provisions for deficiency compensation

Provisions for deficiency compensation

Foreign currency translation

Foreign currency translation

Revenue recognition

Revenue recognition

(a)

Customer controls the provided raw materials and the Group receives the instruction from the customer on providing assembly and testing services and subsequent treatments.

(b)

The Group provides assembly and testing services to create or enhance an asset which solely provided and controlled by the customer. The Group has no right to transfer the asset for another use.

Interest income

Research and development costs

Research and development costs

Research and development costs that do not meet the criteria of internally generated intangible assets of IAS 38 “Intangible Assets” are expensed in the period in which it is incurred.

Borrowing costs

Borrowing costs

Pension and other post-employment benefits

Pension and other post-employment benefits

Share-based payments

Share-based payments

Restricted shares

Restricted shares issued to employees are measured at the fair value of the equity instruments granted at the grant date, and are recognized as compensation cost over the vesting period.

For restricted shares where employees do not need to pay to acquire those shares, if the employees who resign during the vesting period, the Group will recover and retire those shares at no cost.

Income tax

Income tax

Deferred tax liabilities are recognized for all taxable temporary differences, except:

•

Cash and cash equivalents

Cash and cash equivalents

Related parties

Related parties

(a)

A person, or a close member of that person’s family, is related to the Group if that person:

(i)

has control or joint control over the Group;

(ii)

has significant influence over the Group; or

(iii)

is a member of key management personnel of the Group or the Group’s parent.

(b)

An entity is related to the Group if any of the following conditions applies:

(i)

The entity and the Group are members of the same group.

(ii)

One entity is an associate or joint venture of the other entity (or an associate or joint venture of a member of a group of which the other entity is a member).

(iii)

The entity and the Group are joint ventures of the same third party.

(iv)

One entity is a joint venture of a third entity and the other entity is an associate of the third entity.

(v)

The entity is a post-employment benefit plan for the benefit of employees of either the Group or an entity related to the Group.

(vi)

The entity is controlled or jointly controlled by a person identified in (a).

(vii)

A person identified in (a)(i) has significant influence over the entity or is a member of the key management personnel of the entity (or of a parent of the entity).

Subsidiaries

aa)

Subsidiaries

•

the contractual arrangement with the other vote holders of the investee;

•

rights arising from other contractual arrangements; and

•

the Group’s voting rights and potential voting rights

Changes in a parent’s ownership interest in a subsidiary that do not result in the parent losing control of the subsidiary (transactions with non-controlling interests) are accounted for as equity transactions, i.e. transactions with owners in their capacity as owner. Any difference between the amount by which the non-controlling interests are adjusted and the fair value of the consideration paid or received is recognized directly in equity.

Fair value measurement

bb)

Fair value measurement

Level 2: Inputs other than quoted prices from Level 1 that are observable information for the asset or liability, either directly or indirectly.

Level 3: Unobservable inputs for the asset or liability. The fair value of the Group’s financial instruments without active market is included in Level 3.

Capital reorganization

cc)

Capital reorganization

Basis of preparation of financial statements and principal accounting policies (Tables)

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Summary of Ownership Interests in Subsidiaries

Subsidiaries included in the consolidated financial statements:

Percentage of
Ownership (%)

December 31,

Name of investor

Name of investee

Main businesses

Location

2017

2018

The Company

ChipMOS U.S.A., Inc. (“ChipMOS USA”)

Research, development and marketing of semiconductors, circuits, and electronic related products

San Jose, USA

100

The Company

ChipMOS BVI

Holding company

British Virgin Islands

100

Impact on Depreciation Expenses of Current and Future Periods due to Change in Estimated Useful Lives of Certain Properties and Equipment

The impact on depreciation expenses of current and future periods were expected as follows:


	2016			2017			2018			2019
	NT$000			NT$000			NT$000			NT$000
Decrease in depreciation expenses		(119,737	)		(605,259	)		(391,669	)		(164,863	)

Estimated Useful Life for Depreciation of Individual Assets

Depreciation is provided on the straight-line method, based on the estimated useful life of the individual assets, as follows:


Buildings		5 to 51 years
Machinery and equipment		2 to 8 years
Tools		2 to 4 years
Other equipment		2 to 6 years

Segment Information (Tables)

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Financial Segment Information for Operating Segments

Financial segment information is as below:


	2016
	Testing			Assembly			LCDD			Bumping			Others			Elimination			Total continuing operations			Discontinued operations
	NT$000			NT$000			NT$000			NT$000			NT$000			NT$000			NT$000			NT$000
Revenue
External customers		4,587,054			5,880,780			4,920,302			2,999,457			—			—			18,387,593			1,005,166
Inter-segment		—			1,103			—			510			41,670			(43,283	)		—			—

Total revenue		4,587,054			5,881,883			4,920,302			2,999,967			41,670			(43,283	)		18,387,593			1,005,166

Operating profit (loss)		1,346,874			143,220			963,698			(341,356	)		(82,331	)		(31,530	)		1,998,575			(146,263	)
Depreciation expenses		(664,026	)		(635,481	)		(1,167,908	)		(622,412	)		(565	)		488			(3,089,904	)		(141,375	)
Interest income		—			—			—			—			51,756			(13,202	)		38,554			3,753
Interest expense		—			—			—			—			(144,545	)		—			(144,545	)		(606	)
Share of profit (loss) of associates		—			—			—			—			(128,866	)		157,790			28,924			—
Purchase of property, plant and equipment		771,500			554,162			910,457			887,144			49			—			3,123,312			1,567,683


	2017
	Testing			Assembly			LCDD			Bumping			Others			Elimination			Total continuing operations			Discontinued operations
	NT$000			NT$000			NT$000			NT$000			NT$000			NT$000			NT$000			NT$000
Revenue
External customers		4,838,246			5,259,281			4,789,869			3,053,459			—			—			17,940,855			227,095
Inter-segment		—			—			247			—			35,808			(36,055	)		—			—

Total revenue		4,838,246			5,259,281			4,790,116			3,053,459			35,808			(36,055	)		17,940,855			227,095

Operating profit (loss)		1,448,939			(55,198	)		1,285,495			(336,123	)		(100,545	)		(2,687	)		2,239,881			(25,394	)
Depreciation expenses		(673,393	)		(597,500	)		(1,048,587	)		(579,605	)		(503	)		310			(2,899,278	)		—
Interest income		—			—			—			—			53,123			—			53,123			464
Interest expense		—			—			—			—			(190,425	)		—			(190,425	)		(2,414	)
Share of profit (loss) of associates		—			—			—			—			1,347,851			(1,527,342	)		(179,491	)		—
Purchase of property, plant and equipment		836,894			655,879			2,615,153			594,765			—			—			4,702,691			—


	2018
	Testing			Assembly			LCDD			Bumping			Others			Elimination			Total continuing operations			Total continuing operations
	NT$000			NT$000			NT$000			NT$000			NT$000			NT$000			NT$000			US$000
Revenue
External customers		4,790,097			4,679,676			5,694,720			3,315,534			—			—			18,480,027			603,725
Inter-segment		—			—			—			—			35,738			(35,738	)		—			—

Total revenue		4,790,097			4,679,676			5,694,720			3,315,534			35,738			(35,738	)		18,480,027			603,725

Timing of revenue recognition
At a point in time		—			—			—			—			35,738			(35,738	)		—			—
Over time		4,790,097			4,679,676			5,694,720			3,315,534			—			—			18,480,027			603,725

		4,790,097			4,679,676			5,694,720			3,315,534			35,738			(35,738	)		18,480,027			603,725

Operating profit (loss)		1,306,742			(207,700	)		1,226,755			(202,497	)		(23,433	)		(146	)		2,099,721			68,596
Depreciation expenses		(769,660	)		(578,205	)		(1,400,784	)		(627,412	)		(518	)		—			(3,376,579	)		(110,310	)
Interest income		—			—			—			—			49,971			—			49,971			1,633
Interest expense		—			—			—			—			(152,416	)		—			(152,416	)		(4,979	)
Share of profit (loss) of associates		—			—			—			—			(668,377	)		368,276			(300,101	)		(9,804	)
Purchase of property, plant and equipment		1,563,919			321,976			2,732,141			327,251			283			—			4,945,570			161,567

Geographic Information of Revenue

Geographic information of revenue:


	2016		2017		2018		2018
	NT$000		NT$000		NT$000		US$000
Area
ROC		12,728,014		13,152,419		14,751,766		481,926
Japan		1,855,674		2,257,296		1,825,479		59,637
Singapore		3,087,835		1,798,585		1,143,661		37,362
Others		716,070		732,555		759,121		24,800

		18,387,593		17,940,855		18,480,027		603,725

Net Revenue from Customers Representing at Least 10% of Total Revenue

Net revenue from customers representing at least 10% of the total revenue:


	2016				2017				2018				2018
	Amount		%		Amount		%		Amount		%		Amount
	NT$000				NT$000				NT$000				US$000
Customers
Customer A		3,370,285		18		3,434,873		19		3,794,991		21		123,979
Customer K		2,633,431		14		2,742,882		15		2,637,053		14		86,150
Customer C		1,870,675		10		1,530,209		9		1,957,467		11		63,949
Customer I		3,085,190		17		1,798,111		10		1,101,956		6		36,000

The revenue generated from the above customers is mainly from the segments of Assembly and LCDD.

Summary of Contract Assets and Liabilities

The Group has recognized the following contract assets and liabilities in relation to revenue from contracts with customers:


	December 31, 2018
	NT$000		US$000
Contract assets		299,835		9,795

Contract liabilities (Advance payments)		1,432		47

Operating costs and expenses (Tables)

12 Months Ended

Dec. 31, 2018

Analysis of income and expense [abstract]

Summary of Operating Costs and Expenses


	2016			2017		2018		2018
	NT$000			NT$000		NT$000		US$000
Change of finished goods and work in process		(19,498	)		31,977		—		—
Consumption of raw materials and supplies		3,346,540			3,036,350		3,079,909		100,617
Employee benefit expenses		5,317,125			5,895,778		5,606,833		183,170
Depreciation and amortization		3,089,904			2,899,278		3,376,579		110,310
Other expenses		4,745,253			4,530,425		4,464,499		145,851

Total operating costs and expenses		16,479,324			16,393,808		16,527,820		539,948

Employee benefit expenses
Salaries		4,109,393			4,847,433		4,628,039		151,194
Directors remuneration		16,810			27,276		18,456		603
Labor and health insurance		351,232			390,788		406,111		13,267
Pension		183,293			198,502		201,567		6,585
Share-based payments		356,463			123,021		41,043		1,341
Other personnel expenses		299,934			308,758		311,617		10,180

		5,317,125			5,895,778		5,606,833		183,170

Other operating income (expenses), net (Tables)

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Summary of Other Operating Income (Expenses), Net


	2016			2017			2018			2018
	NT$000			NT$000			NT$000			US$000
Gain on disposal of property, plant and equipment, net		2,575			132,777			14,274			466
Impairment on property, plant and equipment		(8,198	)		(956	)		—			—
Gain on disposal of scrapped materials		30,476			27,940			59,380			1,940
Gain on disposal of items purchased on behalf of others		48,812			26,417			31,268			1,021
Royalty income		—			11,998			43,224			1,412
Insurance compensation income		7,033			486,858			147			5
Others		9,608			7,800			(779	)		(25	)

		90,306			692,834			147,514			4,819

Finance costs (Tables)

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Summary of Finance Costs


	2016			2017			2018			2018
	NT$000			NT$000			NT$000			US$000
Interest expenses
Bank loans		157,254			208,486			170,476			5,569
Lease obligations payable		212			708			482			16
Less: Amounts capitalized in qualifying assets		(12,921	)		(18,769	)		(18,542	)		(606	)

		144,545			190,425			152,416			4,979
Finance expense		34,571			26,858			37,832			1,236

		179,116			217,283			190,248			6,215

Other non-operating income (expenses), net (Tables)

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Summary of Other Non-operating Income (Expenses), Net


	2016			2017			2018		2018
	NT$000			NT$000			NT$000		US$000
Interest income
Bank deposits		38,554			53,123			49,051		1,603
Financial assets at amortized cost		—			—			920		30
Foreign exchange gains (losses), net		(195,326	)		(418,970	)		93,104		3,041
Gain on valuation of financial assets at fair value through profit or loss		621			637			1,485		49
Gain on disposal of long-term investment in associates		—			16,929			—		—
Rental income		8,203			11,075			7,819		255
Dividend income		—			—			571		19
Reimbursement of ADSs service charge		—			23,707			13,269		433
Others		—			2,808			6,851		224

		(147,948	)		(310,691	)		173,070		5,654

Income tax expense (Tables)

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Major Components of Income Tax Expense

The major components of income tax expense for the years ended December 31, 2016, 2017 and 2018 are:


	2016			2017		2018			2018
	NT$000			NT$000		NT$000			US$000
Current income tax:
Current income tax on profits for the period		331,144			125,376		326,057			10,652
Income tax (benefit) on unappropriated retained earnings		(174,930	)		246,684		28,165			920
Prior year income tax under estimation		4,527			67,885		3,729			122

Total current income tax		160,741			439,945		357,951			11,694

Deferred income tax:
Relating to origination and reversal of temporary differences		16,379			110,542		101,441			3,314
Impact of change in tax rate		—			—		(2,774	)		(90	)

Total deferred income tax		16,379			110,542		98,667			3,224

Income tax expense reported in the consolidated statements of comprehensive income		177,120			550,487		456,618			14,918

Deferred Tax Charged to Other Comprehensive Income

Deferred tax charged to other comprehensive income:


	2016			2017		2018			2018
	NT$000			NT$000		NT$000			US$000
Unrealized gain on valuation of financial assets at fair value through other comprehensive income		—			—		17,005			556
Remeasurement of defined benefit obligations		(7,375	)		8,642		(11,992	)		(392	)
Impact of change in tax rate		—			—		(887	)		(29	)

		(7,375	)		8,642		4,126			135

Reconciliation of Income Tax Expense and Accounting Profit Before Income Tax

Reconciliation of income tax expense and the accounting profit before income tax:


	2016			2017			2018			2018
	NT$000			NT$000			NT$000			US$000
Tax calculated based on profit before tax and statutory tax rate		214,550			566,649			356,488			11,646
Expenses disallowed (added) by tax regulations		(2,190	)		10,185			14,689			480
Temporary difference not recognized as deferred tax assets		1,306			(85,168	)		(10,951	)		(358	)
Tax exempted (income) expenses by tax regulation		12,057			(256,788	)		66,353			2,168
Taxable loss not recognized as deferred tax assets		54,012			—			—			—
Effect of different tax rates in countries in which the Group operates		10,451			1,040			919			30
Withholding tax		57,337			—			—			—
Impact of change in tax rate		—			—			(2,774	)		(90	)
Prior year income tax under estimation		4,527			67,885			3,729			122
Income tax (benefit) on unappropriated retained earnings		(174,930	)		246,684			28,165			920

Income tax expense reported in the consolidated statements of comprehensive income		177,120			550,487			456,618			14,918

Details of Deferred Tax Assets (Liabilities)

The details of deferred tax assets (liabilities) are as follows:


	January 1,			Retroactive adjustment			Profit or loss			Other comprehensive income (loss)			December 31,			December 31,
	NT$000			NT$000			NT$000			NT$000			NT$000			US$000
Year of 2017
Deferred tax assets
Unrealized exchange losses		—			—			8,167			—			8,167
Loss on inventories		26,324			—			(17,192	)		—			9,132
Property, plant and equipment		80,869			—			(25,375	)		—			55,494
Deferred revenue		41,294			—			(1,809	)		—			39,485
Provisions		11,232			—			10,411			—			21,643
Net defined benefit liability		90,087			—			(2,994	)		(8,642	)		78,451

Deferred tax assets		249,806			—			(28,792	)		(8,642	)		212,372

Deferred tax liabilities
Unrealized exchange gains		(14,155	)		—			14,155			—			—
Property, plant and equipment		(78,388	)		—			(95,905	)		—			(174,293	)

Deferred tax liabilities		(92,543	)		—			(81,750	)		—			(174,293	)

Year of 2018
Deferred tax assets
Unrealized exchange losses		8,167			144			(4,736	)		—			3,575			117
Loss on inventories		9,132			(770	)		(1,130	)		—			7,232			236
Property, plant and equipment		55,494			—			8,689			—			64,183			2,097
Deferred revenue		39,485			—			(5,329	)		—			34,156			1,116
Provisions		21,643			—			(9,247	)		—			12,396			405
Net defined benefit liability		78,451			—			7,889			14,403			100,743			3,291
Investment tax credit		—			—			4,420			—			4,420			144
Others		—			—			11			—			11			1

Deferred tax assets		212,372			(626	)		567			14,403			226,716			7,407

Deferred tax liabilities
Property, plant and equipment		(174,293	)		—			(107,301	)		—			(281,594	)		(9,200	)
Contract assets		—			(8,067	)		8,067			—			—			—
Financial assets at fair value through other comprehensive income		—			(8,636	)		—			(18,529	)		(27,165	)		(887	)

Deferred tax liabilities		(174,293	)		(16,703	)		(99,234	)		(18,529	)		(308,759	)		(10,087	)

Earnings per share ("EPS") (Tables)

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Income and Share Data Used in Basic and Diluted EPS Computations

The following reflects the income and share data used in the basic and diluted EPS computations:


	2016
	Amount after income tax			Weighted average number of ordinary shares outstanding*		Earnings per share
Basic earnings per share	NT$000			In thousands		NT$
Profit (loss) attributable to:
Equity holders of the Company
- Continuing operations		1,829,327					2.13
- Discontinued operations		(122,105	)				(0.14	)

Equity holders of the Company		1,707,222					1.99
Predecessors’ interests		(306,012	)				(0.35	)

	1,401,210			859,644		1.64

Diluted earnings per share
Employees’ compensations					3,035
Restricted shares					4,122

Profit (loss) attributable to:
Equity holders of the Company
- Continuing operations		1,829,327					2.11
- Discontinued operations		(122,105	)				(0.14	)

Equity holders of the Company		1,707,222					1.97
Predecessors’ interests		(306,012	)				(0.35	)

	1,401,210			866,801		1.62

The weighted average number of shares takes into account the weighted average effect of changes in treasury stock transaction during the year.

2017

Amount
after income
tax

Weighted average
number of ordinary
shares outstanding

Earnings
per share

Basic earnings per share

NT$000

In thousands

NT$

Profit attributable to:

Equity holders of the Company

- Continuing operations

981,929

1.16

- Discontinued operations

1,814,953

2.14

2,796,882

846,686

3.30

Diluted earnings per share

Employees’ compensations

14,034

Restricted shares

5,075

Profit attributable to:

Equity holders of the Company

- Continuing operations

981,929

1.13

- Discontinued operations

1,814,953

2.10

2,796,882

865,795

3.23

2018

Amount
after income
tax

Weighted average
number of ordinary
shares outstanding

Earnings
per share

Basic earnings per share

NT$000

In thousands

NT$

US$

Profit attributable to the equity holders of the Company

1,325,824

802,725

1.65

0.05

Diluted earnings per share

Employees’ compensations

7,626

Restricted shares

3,356

Profit attributable to the equity holders of the Company

1,325,824

813,707

1.63

0.05

Non-current financial assets at fair value through profit or loss (Tables)

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Summary of Non-current Financial Assets at Fair Value Through Profit or Loss


	December 31, 2018		December 31, 2018
	NT$000		US$000
Financial assets mandatorily measured at fair value through profit or loss
Foreign partnership interests		10,940		358
Valuation adjustment		531		17

		11,471		375

Summary of Amounts recognized in Profit or Loss in Relation to Financial Assets at Fair Value Through Profit or Loss


	2018		2018
	NT$000		US$000
Financial assets mandatorily measured at fair value through profit or loss
Foreign partnership interests		38		1
Beneficiary certificates*		1,396		46
Derivative instruments		51		2

		1,485		49

Non-current financial assets at fair value through other comprehensive income (Tables)

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Summary of Non-current Financial Assets at Fair Value Through Other Comprehensive Income


	December 31, 2018		December 31, 2018
	NT$000		US$000
Designation of equity instruments
Foreign unlisted stocks		38,534		1,259
Valuation adjustment		135,823		4,437

		174,357		5,696

Summary Amounts recognized in other comprehensive income in relation to the financial assets at fair value through other comprehensive income

Amounts recognized in other comprehensive income in relation to the financial assets at fair value through other comprehensive income are listed below:


	2018		2018
	NT$000		US$000
Financial assets at fair value through other comprehensive income
Foreign unlisted stocks		85,022		2,778

Investment in associates (Tables)

12 Months Ended

Dec. 31, 2018

Investments accounted for using equity method [abstract]

Details of Investment in Associates

Details of investment in associates are as follows:

Country of
incorporation
and business

Measurement
method

December 31, 2017

December 31, 2018

Investee company

Carrying
amount

Ownership

Carrying
amount

Ownership

NT$000

US$000

JMC ELECTRONICS CO., LTD. (“JMC”)

Kaohsiung,
Taiwan

Equity
method

373,276

19.10

406,792

13,290

19.10

Unimos Shanghai

Shanghai,

People’s
Republic
of China

Equity
method

3,060,056

45.02

3,456,949

112,935

45.02

Summarized Financial Information for Investment in Material Associates

The tables below provide summarized financial information for the investment in associates that are material to the Group.

Statements of financial position


	JMC
	December 31, 2017			December 31, 2018			December 31, 2018
	NT$000			NT$000			US$000
Current assets		843,636			1,106,789			36,158
Non-current assets		1,161,620			1,699,498			55,521
Current liabilities		(294,302	)		(817,697	)		(26,714	)
Non-current liabilities		(1,756	)		(103,922	)		(3,395	)

Total net assets		1,709,198			1,884,668			61,570

Group’s share		326,456			359,972			11,760
Goodwill		46,820			46,820			1,530

Carrying amount		373,276			406,792			13,290

Statements of financial position


	Unimos Shanghai
	December 31, 2017			December 31, 2018			December 31, 2018
	NT$000			NT$000			US$000
Current assets		3,380,641			3,946,082			128,915
Non-current assets		2,766,839			3,254,687			106,328
Current liabilities		(460,054	)		(554,160	)		(18,104	)
Non-current liabilities		(489,097	)		(442,306	)		(14,450	)

Total net assets		5,198,329			6,204,303			202,689

Group’s share		2,340,506			2,793,438			91,259
Depreciable assets		703,536			644,718			21,062
Goodwill		22,118			22,118			723
Inter-company transactions and amortization		(6,104	)		(3,325	)		(109	)

Carrying amount		3,060,056			3,456,949			112,935

Statements of comprehensive income

JMC

Year ended December 31,

2016

2017

2018

NT$000

US$000

Revenue

1,667,761

1,322,928

1,931,008

63,084

Profit for the year from continuing operations

136,303

4,414

219,544

7,172

Other comprehensive income (loss), net of income tax

(627

)

2,903

(14,074

)

(460

)

Total comprehensive income

135,676

7,317

205,470

6,712

Dividend received from the associate

5,730

14,325

5,730

187


	Unimos Shanghai
	Year ended December 31,
	2017			2018			2018
	NT$000			NT$000			US$000
Revenue		1,141,415			1,334,196			43,587

Loss for the year from continuing operations		(348,472	)		(629,303	)		(20,559	)
Other comprehensive income, net of income tax		—			—			—

Total comprehensive loss		(348,472	)		(629,303	)		(20,559	)

Dividend received from the associate		—			—			—

Financial assets at amortized cost (Tables)

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Schedule of Income from Financial Assets at Amortized Cost


	December 31, 2018		December 31, 2018
	NT$000		US$000
Current
Time deposits		169,168		5,526

Non-current
Time deposits		30,715		1,003
Restricted bank deposits		68,388		2,234

		99,103		3,237

Amounts recognized in profit or loss in relation to financial assets at amortized cost are listed below:


	2018		2018
	NT$000		US$000
Interest income		920		30

Property, plant and equipment, net (Tables)

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Summary of Property, Plant and Equipment, Net


	Land		Buildings			Machinery and equipment			Tools			Other equipment			Construction in progress and equipment to be inspected			Total			Total
	NT$000		NT$000			NT$000			NT$000			NT$000			NT$000			NT$000			US$000
January 1, 2017
Cost		452,738		11,183,278			47,002,228			3,999,894			3,353,413			1,627,816			67,619,367
Accumulated depreciation and impairment		—		(6,395,332	)		(39,430,608	)		(3,475,451	)		(2,786,790	)		—			(52,088,181	)

		452,738		4,787,946			7,571,620			524,443			566,623			1,627,816			15,531,186
Less: Property, plant and equipment classified as held for sale		—		(710,191	)		(433,688	)		(90,460	)		(168,314	)		(631,315	)		(2,033,968	)

		452,738		4,077,755			7,137,932			433,983			398,309			996,501			13,497,218

January 1, 2017		452,738		4,077,755			7,137,932			433,983			398,309			996,501			13,497,218
Additions		—		211,098			2,007,767			571,601			195,957			1,716,268			4,702,691
Disposals		—		—			(30,066	)		(2,302	)		(1,865	)		—			(34,233	)
Reclassifications		—		141,400			1,535,619			44,882			22,149			(1,744,050	)		—
Depreciation expenses		—		(511,167	)		(1,837,482	)		(357,695	)		(192,934	)		—			(2,899,278	)
Impairment losses		—		—			—			—			(956	)		—			(956	)
Exchange adjustments		—		—			(43	)		—			(88	)		—			(131	)

December 31, 2017		452,738		3,919,086			8,813,727			690,469			420,572			968,719			15,265,311

December 31, 2017
Cost		452,738		9,809,970			45,778,207			4,004,703			2,624,083			968,719			63,638,420
Accumulated depreciation and impairment		—		(5,890,884	)		(36,964,480	)		(3,314,234	)		(2,203,511	)		—			(48,373,109	)

		452,738		3,919,086			8,813,727			690,469			420,572			968,719			15,265,311

January 1, 2018
Cost		452,738		9,809,970			45,778,207			4,004,703			2,624,083			968,719			63,638,420			2,079,008
Accumulated depreciation and impairment		—		(5,890,884	)		(36,964,480	)		(3,314,234	)		(2,203,511	)		—			(48,373,109	)		(1,580,304	)

		452,738		3,919,086			8,813,727			690,469			420,572			968,719			15,265,311			498,704

January 1, 2018		452,738		3,919,086			8,813,727			690,469			420,572			968,719			15,265,311			498,704
Additions		—		247,186			2,445,313			591,229			172,652			1,489,190			4,945,570			161,567
Disposals		—		—			(904	)		(11,745	)		(2,067	)		—			(14,716	)		(481	)
Reclassifications		—		199,724			1,154,663			7,604			26,026			(1,388,017	)		—			—
Depreciation expenses		—		(457,265	)		(2,180,718	)		(535,378	)		(203,218	)		—			(3,376,579	)		(110,310	)
Exchange adjustments		—		—			12			—			23			—			35			1

December 31, 2018		452,738		3,908,731			10,232,093			742,179			413,988			1,069,892			16,819,621			549,481

December 31, 2018
Cost		452,738		10,254,531			48,274,171			4,402,711			2,610,893			1,069,892			67,064,936			2,190,948
Accumulated depreciation and impairment		—		(6,345,800	)		(38,042,078	)		(3,660,532	)		(2,196,905	)		—			(50,245,315	)		(1,641,467	)

		452,738		3,908,731			10,232,093			742,179			413,988			1,069,892			16,819,621			549,481

Capitalization Interest and Capitalization Interest Rate Applied Related to Property, Plant and Equipment

Amount of borrowing costs capitalized as part of property, plant and equipment and the range of the interest rates for such capitalization are as follows:


	2017		2018		2018
	NT$000		NT$000		US$000
Capitalization interest		18,769		18,542		606
Capitalization interest rate applied		1.7624%		1.7582%		1.7582%

Inventories (Tables)

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Summary of Inventories

	December 31, 2017
	Cost		Allowance for impairment losses			Carrying amount
	NT$000		NT$000			NT$000
Raw materials		1,769,917		(49,183	)		1,720,734
Work in process		180,252		(4,163	)		176,089
Finished goods		32,784		(368	)		32,416

		1,982,953		(53,714	)		1,929,239

December 31, 2018

Cost

Allowance for
impairment losses

Carrying amount

NT$000

US$000

Raw materials

1,814,992

(36,157

)

1,778,835

58,113

Cost of Inventories Recognized as an Expense

The cost of inventories recognized as an expense for the year:


	2017			2018			2018
	NT$000			NT$000			US$000
Cost of revenue		14,766,555			15,057,605			491,918
Loss on abandonment		38,301			5,497			179
Reversal of inventory valuation and obsolescence loss		(101,127	)		(13,070	)		(427	)

		14,703,729			15,050,032			491,670

Accounts and notes and other receivables (Tables)

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Summary of Accounts and Notes and Other Receivables


	December 31, 2017		December 31, 2018			December 31, 2018
	NT$000		NT$000			US$000
Accounts receivable		4,013,705		4,747,834			155,108
Notes receivable		2,029		1,595			52
Less: Loss allowance		—		(2,141	)		(70	)

		4,015,734		4,747,288			155,090

Other receivables		56,716		63,049			2,060
Less: Loss allowance		—		(12	)		(1	)

		56,716		63,037			2,059

		4,072,450		4,810,325			157,149

Aging of Accounts Receivable which are Past Due but not Impaired

The aging analysis of accounts receivable based on past due date is as follows:


	December 31, 2017		December 31, 2018		December 31, 2018
	NT$000		NT$000		US$000
Current		3,997,833		4,595,300		150,124
Within 1 month		10,482		18,807		615
1 – 2 months		477		131,787		4,305
2 – 3 months		426		1,436		47
3 – 4 months		1,431		180		6
Over 4 months		3,056		324		11

		4,013,705		4,747,834		155,108

Non-current assets held for sale and discontinued operations (Tables) - Discontinued operations: Unimos Shanghai [member]

12 Months Ended

Dec. 31, 2018

Statement [LineItems]

Cash Flow Information of Discontinued Operations

The cash flow information of the discontinued operations is as follows:


	2016			2017
	NT$000			NT$000
Net cash used in operating activities		(1,109,029	)		(109,079	)
Net cash used in investing activities		(1,331,564	)		(272,925	)
Net cash generated from financing activities		1,463,664			461,312
Effect of foreign exchange rate changes		(61,336	)		(19,874	)

Net increase (decrease) in cash and cash equivalents		(1,038,265	)		59,434

Assets, Liabilities and Equity of Disposal Group Classified as Held for Sale

Equity of disposal group classified as amounts recognized in other comprehensive income and accumulated in equity relating to non-current assets held for sale :


	December 31,
	2016
	NT$000
Foreign currency translation reserve		287,645

Cumulative Income or Expense Recognized in Other Comprehensive Income Relating to Disposal Group Classified as Held for Sale

Cumulative income or expense recognized in other comprehensive income relating to disposal group classified as held for sale:


	2016			2017
	NT$000			NT$000
Exchange differences on translation of foreign operations		(195,972	)		(287,645	)

Results of Discontinued Operations

The results of discontinued operations are as follows:


	2016			2017
	NT$000			NT$000
Revenue		1,005,166			227,095
Cost of revenue		(986,004	)		(195,078	)
Operating expenses		(179,178	)		(58,840	)
Other operating income (expenses), net		13,753			1,429
Non-operating income (expenses), net		24,158			(2,887	)

Loss from discontinued operations before income tax		(122,105	)		(28,281	)
Income tax expense		—			—

Loss from discontinued operations after income tax		(122,105	)		(28,281	)
Gain on disposal of discontinued operations		—			1,843,234

Profit (loss) from discontinued operations		(122,105	)		1,814,953

Discontinued operations’ revenue is mainly from the segments of testing and assembly.

Issued capital (Tables)

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Summary of Issued Capital

December 31,
2016

December 31,
2017

December 31,
2018

in thousands

Authorized shares

Ordinary shares

1,450,000

970,000

December 31,
2016

December 31,
2017

December 31,
2018

in thousands

Ordinary shares issued and fully paid

Ordinary shares

886,966

886,297

752,858

Issued capital (NT$000)

8,869,663

8,862,971

7,528,577

(US$245,952
thousand

)

Movement of Ordinary Shares Issued

The movement of ordinary shares issued is set out below:


	2016			2017			2018
	in thousands			in thousands			in thousands
January 1		896,206			886,966			886,297
Restricted shares		435			—			—
Unearned restricted shares – cancelled		—			(669	)		(502	)
Share cancellation		—			—			(4,515	)
Issuance of ordinary shares for capital reorganization (Note 31)		512,405			—			—
Cancellation of ordinary shares from capital reorganization (Note 31)		(522,080	)		—			—
Capital reduction		—			—			(128,422	)

December 31		886,966			886,297			752,858

Capital surplus and retained earnings (Tables)

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Summary of Capital Surplus

Details of the Group’s capital surplus are set out below:


	December 31, 2016		December 31, 2017		December 31, 2018		December 31, 2018
	NT$000		NT$000		NT$000		US$000
Share premium		6,473,471		5,873,743		5,873,743		191,890
Restricted shares		408,051		390,401		382,506		12,496
Others		7,304		7,304		7,304		239

		6,888,826		6,271,448		6,263,553		204,625

Summary of Distribution Towards Legal Reserve and Cash Dividend

(e)

The distribution of 2015, 2016 and 2017 were resolved at the shareholders’ meetings on May 31, 2016, May 26, 2017 and June 26, 2018, respectively. Details are summarized below:


	2015				2016				2017
	Amount		Distribution per share		Amount		Distribution per share		Amount		Distribution per share
	NT$000		NT$		NT$000		NT$		NT$000		NT$
Legal reserve		223,047				28,680				302,653
Cash dividend		1,792,553		2.09		257,026		0.30		256,806		0.30
Cash distribution from capital surplus		—		—		599,728		0.70		—		—

Treasury stock (Tables)

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Movement of Treasury Stock

The movement of treasury stock is set out below:


	2016				2017				2018
	Shares (in thousands)		Amount (NT$000)		Shares (in thousands)		Amount (NT$000)		Shares (in thousands)			Amount (NT$000)			Amount (US$000)
January 1		—		—		30,085		1,007,654		30,085			1,007,654			32,919
Treasury stock (repurchased)		30,085		1,007,654		—		—		—			—			—
Capital reduction		—		—		—		—		(4,515	)		(45,151	)		(1,475	)

December 31		30,085		1,007,654		30,085		1,007,654		25,570			962,503			31,444

Bank loans (Tables)

12 Months Ended

Dec. 31, 2018

Long-term bank loans [Member]

Statement [LineItems]

Summary of Bank Loans


Type of loans	Period and payment term	December 31, 2017			December 31, 2018			December 31, 2018
		NT$000			NT$000			US$000
Syndicated bank loan	Borrowing period is from May 30, 2018 to May 30, 2023; interest is repayable monthly; principal is repayable semi-annually from November 30, 2018		—			9,822,000			320,876
Syndicated bank loan	Borrowing period is from June 30, 2016 to June 30, 2021; interest is repayable monthly; principal is repayable semi-annually from December 30, 2017		9,675,301			—			—
Less: Fee on syndicated bank loan			(33,280	)		(32,482	)		(1,061	)
Less: Current portion (fee included)			(2,143,168	)		(747,422	)		(24,418	)

			7,498,853			9,042,096			295,397

Interest rate range			1.7895%			1.7895%			1.7895%

Unused credit lines of long-term bank loans NT$000			2,400,000			1,800,000

Details of Repayment Schedule in Respect of Bank Loans

Details of the repayment schedule in respect of the bank loans are as follows:

December 31,
2017

December 31,
2018

NT$000

US$000

Within 1 year

2,143,168

747,422

24,418

1 to 5 years

7,498,853

9,042,096

295,397

9,642,021

9,789,518

319,815

Short-term bank loans [member]

Statement [LineItems]

Summary of Bank Loans

December 31,
2017

December 31,
2018

NT$000

US$000

Unsecured bank loans

969,353

—

Interest rate range

0.55%~1.71%

—

Unused Credit Lines of Bank Loans

Unused credit lines of short-term bank loans are as follows:


	December 31, 2017		December 31, 2018
NT$000		3,028,357		3,252,500
US$000		80,000		90,000

Retirement benefit plans (Tables)

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Summary of Amounts Recognized in Statements of Financial Position

(b)

The amounts recognized in the statements of financial position are as follows:


	December 31, 2017			December 31, 2018			December 31, 2018
	NT$000			NT$000			US$000
Present value of defined benefit obligations		(838,543	)		(910,081	)		(29,731	)
Fair value of plan assets		360,017			389,316			12,718

Net defined benefit liability		(478,526	)		(520,765	)		(17,013	)

Summary of Movements in net Defined Benefit Liability

(c)

Movements in net defined benefit liability are as follows:


	2017
	Present value of defined benefit obligations			Fair value of plan assets			Net defined benefit liability
	NT$000			NT$000			NT$000
January 1		(894,163	)		347,195			(546,968	)
Current service cost		(386	)		—			(386	)
Interest (expense) income		(13,236	)		5,226			(8,010	)

		(907,785	)		352,421			(555,364	)

Remeasurements:
Return of plan assets (excluding the amount included in interest income or expense)		—			(1,842	)		(1,842	)
Financial assumption movement effect		28,506			—			28,506
Experience adjustments		24,174			—			24,174

		52,680			(1,842	)		50,838

Pension fund contribution		—			26,000			26,000
Paid pension		16,562			(16,562	)		—

December 31		(838,543	)		360,017			(478,526	)


	2018
	Present value of defined benefit obligations			Fair value of plan assets			Net defined benefit liability
	NT$000			NT$000			NT$000			US$000
January 1		(838,543	)		360,017			(478,526	)		(15,633	)
Current service cost		(382	)		—			(382	)		(12	)
Interest (expense) income		(14,429	)		6,291			(8,138	)		(266	)

		(853,354	)		366,308			(487,046	)		(15,911	)

Remeasurements:
Return of plan assets (excluding the amount included in interest income or expense)		—			8,145			8,145			266
Financial assumption movement effect		(56,934	)		—			(56,934	)		(1,860	)
Experience adjustments		(11,172	)		—			(11,172	)		(365	)

		(68,106	)		8,145			(59,961	)		(1,959	)

Pension fund contribution		—			26,242			26,242			857
Paid pension		11,379			(11,379	)		—			—

December 31		(910,081	)		389,316			(520,765	)		(17,013	)

Principal Actuarial Assumptions

(e)	The principal actuarial assumptions used were as follows:


	2017		2018
Discount rate		1.75%		1.25%
Future salary increases		3.50%		3.50%

Sensitivity Analysis of Present Value of Defined Benefit Obligations Effected by Changes of Significant Actuarial Assumptions

The sensitivity analysis of present value of defined benefit obligations effected by the changes of significant actuarial assumptions at December 31, 2017 and 2018 are shown below:


	Discount rate					Future salary increase
	Increase 0.25%			Decrease 0.25%		Increase 0.25%		Decrease 0.25%
December 31, 2017
Effect on present value of defined benefit obligations		(27,192	)		28,506		27,955		(26,816	)

December 31, 2018
Effect on present value of defined benefit obligations		(29,052	)		30,430		29,692		(28,513	)

Analysis of Timing of the Future Pension Payment

(g)

As of December 31, 2018, the weighted average duration of that retirement plan is 13.2 years. The analysis of timing of the future pension payment is as follows:


	December 31, 2018
	NT$000		US$000
Within 1 year		32,904		1,075
1-2 years		35,835		1,170
2-5 years		105,665		3,452
5-10 years		189,400		6,188

		363,804		11,885

Other Payables (Tables)

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Summary of Other Payables


	December 31, 2017		December 31, 2018		December 31, 2018
	NT$000		NT$000		US$000
Salaries and bonus payable		601,239		595,575		19,457
Interest payable		2,854		963		31
Pension payable		32,402		32,038		1,047
Employees’ compensation payable		371,912		212,391		6,939
Directors’ remuneration payable		18,596		9,951		325
Other expense payable		953,179		827,564		27,036

		1,980,182		1,678,482		54,835

Current provisions (Tables)

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Movements in Provisions

Movements in provisions are as follows:


	2018
	Provisions for deficiency compensation
	NT$000			US$000
January 1		57,155			1,867
Provision		14,211			465
Reversal		(24,451	)		(799	)
Payment		(17,563	)		(574	)

December 31		29,352			959

Significant commitments and contingencies (Tables)

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Future Minimum Lease Obligation Payable under Operating Lease Contracts

Future minimum lease obligation payable under those leases are as follows:


	December 31, 2017		December 31, 2018		December 31, 2018
	NT$000		NT$000		US$000
Within 1 year		39,342		68,631		2,242
1 to 5 years		130,182		140,137		4,578
Over 5 years		139,899		111,446		3,641

		309,423		320,214		10,461

Capital Expenditures that are Contracted for, but not Provided for

Capital expenditures that are contracted for, but not provided for are as follows:

December 31,
2017

December 31,
2018

NT$000

US$000

Property, plant and equipment

2,178,262

2,508,797

81,960

Supplementary cash flow information (Tables)

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Partial Cash Paid for Investing and Financing Activities

Partial cash paid for investing and financing activities

Property, plant and equipment


	2016			2017			2018			2018
	NT$000			NT$000			NT$000			US$000
Purchase in property, plant and equipment		4,690,995			4,849,331			4,945,570			161,567
Add: Beginning balance of payable to contractors and equipment suppliers		523,962			839,983			713,313			23,303
Add: Beginning balance of lease payable		—			94,952			29,842			975
Less: Ending balance of payable to contractors and equipment suppliers		(647,486	)		(878,065	)		(1,516,735	)		(49,550	)
Less: Ending balance of lease payable		(96,006	)		(84,192	)		(17,792	)		(581	)
Less: Transfer from prepaid equipment (shown as “Other non-current assets”)		—			(139,304	)		—			—

Cash paid for acquisition of property, plant and equipment		4,471,465			4,682,705			4,154,198			135,714

Capital reorganization


	2016			2017		2018		2018
	NT$000			NT$000		NT$000		US$000
Net assets acquired from ChipMOS Bermuda		12,987,736			—		—		—
Less: Issuance of shares		(9,779,426	)		—		—		—

Cash consideration		3,208,310			—		—		—
Directly attributable transaction cost		133,311			—		—		—

Cash paid for capital reorganization		3,341,621			—		—		—

Disposal of a subsidiary


	2016		2017			2018		2018
	NT$000		NT$000			NT$000		US$000
Disposal of a subsidiary		—		2,166,151			—		—
Add: Ending balance of other payables*		—		64,393			—		—
Less: Cash and cash equivalents of discontinued operations		—		(449,331	)		—		—

Cash received from disposal of a subsidiary		—		1,781,213			—		—

Reconciliation of Liabilities Arising from Financing Activities

Reconciliation of liabilities arising from financing activities


						Non-Cash flow
	As of January 1, 2017		Cash flow			Amortization of loans fee		As of December 31, 2017
	NT$000		NT$000			NT$000		NT$000
Long-term bank loans (include the current portion)		10,750,005		(1,124,699	)		16,715		9,642,021
Short-term bank loans		—		969,353			—		969,353
Guarantee deposits		1,404		(33	)		—		1,371

		10,751,409		(155,379	)		16,715		10,612,745


						Non-Cash flow
	As of January 1, 2018		Cash flow			Amortization of loans fee		As of December 31, 2018
	NT$000		NT$000			NT$000		NT$000		US$000
Long-term bank loans (include the current portion)		9,642,021		110,250			37,247		9,789,518		319,815
Short-term bank loans		969,353		(969,353	)		—		—		—
Guarantee deposits		1,371		(279	)		—		1,092		35

		10,612,745		(859,382	)		37,247		9,790,610		319,850

Related party transactions (Tables)

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Summary of Significant Related Party Transactions

Significant related party transactions

(a)

Subcontracting fee

2016

2017

2018

NT$000

US$000

Unimos Shanghai

—

41,183

(b)

Purchases of materials


	2016		2017		2018		2018
	NT$000		NT$000		NT$000		US$000
JMC		—		130		132,494		4,329
Unimos Shanghai		—		906		3,775		123

		—		1,036		136,269		4,452

(c)

Disposal of property, plant and equipment


	2017
	Selling price		Gain on disposal
	NT$000		NT$000
Unimos Shanghai		21,982		20,240

There were no disposal of property, plant, and equipment to related parties for the years ended December 31, 2016 and 2018.

(d)

Acquisition of property, plant and equipment


	2018		2018
	NT$000		US$000
Unimos Shanghai		61,904		2,022

Key Management Personnel Compensation

Key management personnel compensation


	2016		2017		2018		2018
	NT$000		NT$000		NT$000		US$000
Salaries and short-term employee benefits		152,319		188,105		151,095		4,936
Post-employment compensation		3,335		5,622		2,067		68
Share-based payments		109,255		18,736		6,763		221

		264,909		212,463		159,925		5,225

Pledged or mortgaged assets (Tables)

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Certain Assets Provided as Collateral Mainly for Long-term Bank Loans and Leases

The Group provided certain assets as collateral mainly for long-term bank loans (Note 24) and leases, which were as follows:


	December 31, 2017		December 31, 2018		December 31, 2018
	NT$000		NT$000		US$000
Non-current financial assets at amortized cost		—		68,388		2,234
Property, plant and equipment, net (Note 16)		7,164,089		9,672,238		315,983
Other non-current financial assets		70,241		—		—

		7,234,330		9,740,626		318,217

Financial risk management and fair values of financial instruments (Tables)

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Summary of Financial Instruments by Category

Financial instruments by category


	December 31, 2017		December 31, 2018		December 31, 2018
	NT$000		NT$000		US$000
Financial assets
Financial assets at fair value through profit or loss
Financial assets mandatorily measured at fair value through profit or loss		—		11,471		375
Financial assets at fair value through other comprehensive income
Designation of equity instruments		—		174,357		5,696
Available-for-sale financial assets
Non-current financial assets carried at cost		20,890		—		—
Financial assets at amortized cost/loans and receivables
Cash and cash equivalents		8,035,714		4,642,522		151,667
Financial assets at amortized cost		—		268,271		8,763
Accounts and notes receivable		4,015,734		4,747,288		155,090
Accounts receivable – related parties		11		140		5
Other receivables		56,716		63,037		2,059
Other receivables – related parties		4,534		3,131		102
Refundable deposits		21,342		22,006		719
Other financial assets		70,241		—		—

		12,225,182		9,932,223		324,476


	December 31, 2017		December 31, 2018		December 31, 2018
	NT$000		NT$000		US$000
Financial liabilities
Financial liabilities at amortized cost
Short-term bank loans		969,353		—		—
Accounts payable		687,960		637,271		20,819
Accounts payable – related parties		226		347		11
Payables to contractors and equipment suppliers		713,313		1,516,735		49,550
Other payables		1,980,182		1,678,482		54,835
Other payables – related parties		36		218		7
Long-term bank loans (including current portion)		9,642,021		9,789,518		319,815
Guarantee deposits		1,371		1,092		35

		13,994,462		13,623,663		445,072

Information on Assets and Liabilities Denominated in Foreign Currencies whose Values would be Materially Affected by Exchange Rate Fluctuations

The information on the assets and liabilities denominated in foreign currencies whose values would be materially affected by the exchange rate fluctuations is as follows:


	December 31, 2017
	Foreign currency		Exchange rate		Carrying amount (NT$000)
Financial assets
Monetary items
US$000		208,066		29.7600		6,192,044
JPY000		798,254		0.2642		210,899
RMB000		167,484		4.5650		764,564
Financial liabilities
Monetary items
US$000		16,036		29.7600		477,231
JPY000		1,071,432		0.2642		283,072


	December 31, 2018
	Foreign currency		Exchange rate		Carrying amount (NT$000)
Financial assets
Monetary items
US$000		170,270		30.7150		5,229,843
JPY000		177,557		0.2782		49,396
RMB000		8,850		4.4720		39,577
Financial liabilities
Monetary items
US$000		18,230		30.7150		559,934
JPY000		2,436,140		0.2782		677,734

Details of Exposure to Currency Risk Arising from Recognized Monetary Assets or Liabilities Denominated in a Currency Other Than Functional Currency


	2017
	Change in exchange rate		Effect on profit (NT$000)		Effect on other comprehensive income (NT$000)
Financial assets
US$000		5%		309,602		—
JPY000		5%		10,545		—
RMB000		5%		38,228		—
Financial liabilities
US$000		5%		23,862		—
JPY000		5%		14,154		—


	2018
	Change in exchange rate		Effect on profit (NT$000)		Effect on other comprehensive income (NT$000)
Financial assets
US$000		5%		261,492		—
JPY000		5%		2,470		—
RMB000		5%		1,979		—
Financial liabilities
US$000		5%		27,997		—
JPY000		5%		33,887		—

Summary of Loss Rate Methodology

On December 31, 2018, the loss rate methodology is as follows:


	December 31, 2018
	Contract assets			Accounts receivable (including related parties)			Other receivables (including related parties)
	NT$000			NT$000			NT$000
Expected loss rate		0.045%			0.045%			0.045%
Total carrying amount		299,970			4,747,974			66,181
Loss allowance		(135	)		(2,141	)		(13	)

Summary of Movements in Relation to Loss Allowance for Contract Assets, Accounts Receivable and Other Receivables

Under the simplified approach, movements in relation to loss allowance for contract assets, accounts receivable, and other receivables are as follows:


	2018
	Contract assets			Accounts receivable (including related parties)			Other receivables (including related parties)
	NT$000			NT$000			NT$000
January 1_ IAS 39		—			—			—
Adjustments for applying new standards		(115	)		(1,819	)		(7	)

January 1_IFRS 9		(115	)		(1,819	)		(7	)
Provision for impairment loss		(20	)		(322	)		(7	)
Reversal of impairment loss		—			—			1

December 31		(135	)		(2,141	)		(13	)

Summary Of Investments Financial Assets At Amortized cost

For investments in financial assets at amortized cost, the credit rating levels are presented below:

December 31, 2018

By lifetime

12 months

Increase in
credit risk

Impairment
of credit

Total

NT$000

Financial assets at amortized cost Bank deposits (Note)

268,271

—

268,271

Maturity Profile of Non-derivative Financial Liabilities Based on Contracted Undiscounted Payments

The maturity profile of the Group’s non-derivative financial liabilities as of December 31, 2017 and 2018 based on the contracted undiscounted payments is as follows:


	December 31, 2017
	Within 1 year		1 to 5 years		Over 5 years		Total
	NT$000		NT$000		NT$000		NT$000
Short-term bank loans		971,813		—		—		971,813
Long-term bank loans (including current portion)		2,321,459		7,740,267		—		10,061,726
Accounts payable and payables to contractors and equipment suppliers (including related parties)		1,401,499		—		—		1,401,499
Other payables (including related parties)		1,980,218		—		—		1,980,218
Lease obligations payable		12,266		18,266		—		30,532
Guarantee deposits		—		—		1,371		1,371

		6,687,255		7,758,533		1,371		14,447,159


	December 31, 2018
	Within 1 year		1 to 5 years		Over 5 years		Total		Total
	NT$000		NT$000		NT$000		NT$000		US$000
Long-term bank loans (including current portion)		927,243		9,549,327		—		10,476,570		342,260
Accounts payable and payables to contractors and equipment suppliers (including related parties)		2,154,353		—		—		2,154,353		70,380
Other payables (including related parties)		1,678,700		—		—		1,678,700		54,842
Lease obligations payable		18,000		—		—		18,000		588
Guarantee deposits		—		—		1,092		1,092		35

		4,778,296		9,549,327		1,092		14,328,715		468,105

Summary of Natures of Assets and Liabilities

(i)

The related information of natures of the assets and liabilities is as follows:

December 31, 2018

Level 1

Level 2

Level 3

Total

NT$000

US$000

Assets

Recurring fair value measurements

Financial assets at fair value through profit or loss

- Foreign partnership interests

—

11,471

375

Financial assets at fair value through other comprehensive income

- Foreign unlisted stocks

—

174,357

5,696

—

185,828

6,071

Summary of Movements of Level 3

(d)

The following table shows the movements of Level 3 for the year ended December 31, 2018:


	December 31, 2018
	Debt instruments				Equity instruments
	NT$000		US$000		NT$000		US$000
January 1		—		—		—		—
Effects on initial application of IFRS 9		11,433		374		89,335		2,918
Gains or losses recognized in profit or loss
Recorded as non-operating income (expenses)		38		1		—		—
Gains or losses recognized in other comprehensive income
Recorded as unrealized gains on valuation of financial assets at fair value through other comprehensive income		—		—		85,022		2,778

December 31		11,471		375		174,357		5,696

Summary of Qualitative Information and Sensitivity Analysis of Changes in Significant Unobservable Inputs Under Valuation Model Used in Level 3 Fair Value Measurement

(f)	The following is the qualitative information and sensitivity analysis of changes in significant unobservable inputs under valuation model used in Level 3 fair value measurement:

Fair value as of
December 31,
2018
(NT$000)

Valuation
technique

Significant

unobservable
input

Range
(weighted
average
method)

Relationship of inputs

to fair value

Non-derivative debt instrument:

Foreign partnership interests

11,471

Discounted cash flow

Discount rate

0.35%

The lower the discount rate, the higher the fair value

Non-derivative equity instrument:

Foreign unlisted stocks

174,357

Comparable companies

Price to book ratio multiple

1.19

The higher the multiple, the higher the fair value

Enterprise value to EBITDA multiple

7.69

The higher the multiple, the higher the fair value

Discount for lack of marketability

15.80%

The higher the discount for lack of marketability, the lower the fair value

Summary of Effect of Profit or Loss or of Other Comprehensive Income from Financial Assets Categorized

(g)


			December 31, 2018
			Recognized in profit or loss				Recognized in other comprehensive income
	Input	Change	Favorable change		Unfavorable change		Favorable change		Unfavorable change
			NT$000		NT$000		NT$000		NT$000
Financial assets
Foreign partnership interests	Discount rate	Note		—		—		—		—
Foreign unlisted stocks	Price to book ratio multiple	± 1%		—		—		69		68
	Enterprise to EBITDA multiple	± 1%		—		—		1,563		1,512
	Discount for lack of marketability	± 1%		—		—		2,093		2,050

				—		—		3,725		3,630

Share-based payments (Tables)

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Years of Service and Performance Conditions of Restricted Shares

When the employees of ChipMOS Taiwan accomplished the following years of service and performance conditions, the received restricted shares will be vested based on the vesting ratio.


	The 1^st year	The 2^nd year	The 3^rd year
Years of service following the receipt of restricted shares	Continuous service for one year	Continuous service for two years	Continuous service for three years
Grade of performance appraisal	>=B+	>=B+	>=B+
Compliance of terms agreed by the staff and the Company	No violation	No violation	No violation
Vesting ratio of numbers of restricted shares received	30%	30%	40%

Capital management (Tables)

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Summary of Group Monitors Capital using Liabilities to Assets Ratio

The Group monitors capital using the liabilities to assets ratio, the percentages of which as of December 31, 2017 and 2018 were as follows:

December 31, 2017

December 31, 2018

NT$000

US$000

Total liabilities

15,138,993

15,112,545

493,713

Total assets

33,259,942

33,133,718

1,082,448

Liabilities to assets ratio

45.52%

45.61%

Financial Statements Schedule: Valuation and Qualifying Accounts (Tables)

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Disclosure Of Details Of Valuation And Qualifying Accounts


	January 1		Additions charged to expense		Deduction / Write-offs			Exchange difference on translations of foreign financial statement			Non-current assets held for sale			December 31
	NT$000		NT$000		NT$000			NT$000			NT$000			NT$000
Year of 2016 :

Allowance for impairment of property, plant and equipment		1,994,715		8,198		(45,319	)		(118,046	)		(1,480,278	)		359,270

Allowance for impairment of obsolescence and decline in market value of inventories		95,036		66,894		—			(557	)		(6,532	)		154,841

Allowance for impairment of accounts receivable		—		87		—			—			—			87

Year of 2017 :

Allowance for impairment of property, plant and equipment		359,270		956		(39,771	)		—			—			320,455

Allowance for impairment of obsolescence and decline in market value of inventories		154,841		—		(101,127	)		—			—			53,714

Allowance for impairment of accounts receivable		87		—		(87	)		—			—			—

Year of 2018 :

Allowance for impairment of property, plant and equipment		320,455		—		(2,862	)		—			—			317,593

Allowance for impairment of obsolescence and decline in market value of inventories		53,714		—		(17,557	)		—			—			36,157

Loss allowance for accounts receivable*		1,819		322		—			—			—			2,141

Effects on initial application of IFRS 9 and information for the years ended December 31, 2016 and 2017 in conformity with IAS 39 (Tables)

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Summary of Carrying Amount of Financial Assets Transferred

c)	The carrying amount of financial assets transferred from December 31, 2017 under IAS 39 to January 1, 2018 under IFRS 9 is reconciled as follows:


																	Effects
	Note		Measured at cost			Measured at fair value through profit or loss		Measured at fair value through other comprehensive income		Other financial assets			Measured at amortized cost		Total		Retained earnings		Other equity interest
			NT$000			NT$000		NT$000		NT$000			NT$000		NT$000		NT$000		NT$000
IAS 39				20,890			—		—		70,241			—		91,131		—		—
Transferred into and measured at fair value through profit or loss		(c)		(10,940	)		10,940		—		—			—		—		—		—
Transferred into and measured at fair value through other comprehensive income		(b)		(9,950	)		—		9,950		—			—		—		—		—
Transfer into and measured at amortized cost		(a)		—			—		—		(70,241	)		70,241		—		—		—
Fair value adjustment		(b)(c)		—			493		50,801		—			—		51,294		493		79,385
Impairment loss adjustment		(b)		—			—		28,584		—			—		28,584		28,584		(28,584	)
Income tax adjustment		(b)		—			—		—		—			—		—		—		(8,636	)

IFRS 9				—			11,433		89,335		—			70,241		171,009		29,077		42,165

(a)

(b)

(c)

Summary of Significant Accounts

The significant account as of December 31, 2017 is as follows:

Available-for-sale financial assets


	December 31, 2017
	NT$000
Unlisted equity investments, at cost		49,474
Less: Allowance for impairment losses		(28,584	)

		20,890

Summary of Ageing of Accounts Receivable which are Past Due But Not Impaired

(d)

The aging of accounts receivable which are past due but not impaired is as follows:


	December 31, 2017
	NT$000
£ 1 month		10,482
1-2 months		477
2-3 months		426
3-4 months		1,431
> 4 months		3,056

		15,872

Summary of Movements in Allowance for Impairment of Accounts and Other Receivables

(e)

The movements in allowance for impairment of accounts and other receivables during the year is as follows:


	Accounts receivable			Other receivables
	NT$000			NT$000
January 1, 2017		87			—
Reversal of allowance for impairment losses		(87	)		—

December 31, 2017		—			—

Effects on initial application of IFRS 15 and information for the years ended December 31, 2016 and 2017 in conformity with IAS 18 (Tables)

12 Months Ended

Dec. 31, 2018

Text block [abstract]

Summary of Movements in Allowance for Impairment of Accounts and Other Receivables

c)	The impact and description on consolidated statement of financial position and statement of comprehensive income if the Group continues adopting above accounting policies as of and for the year ended December 31, 2018 are as follows:


			December 31, 2018
Consolidated statement of financial position items	Description		Balance under IFRS 15		Balance under previous accounting policies		Impact on accounting policy change
			NT$000		NT$000		NT$000
Contract assets		(d)(f)(g)		299,835		—		299,835
Inventories		(e)		1,778,835		2,016,106		(237,271	)
Deferred tax assets		(h)		226,716		226,635		81
Contract liabilities		(i)		1,432		—		1,432
Receipts in advance		(i)		1,013		2,445		(1,432	)
Current provisions		(j)		29,352		61,979		(32,627	)
Current refund liabilities		(j)		32,627		—		32,627
Retained earnings				3,602,663		3,540,018		62,645


			2018
Consolidated statement of comprehensive income items	Description		Balance under IFRS 15			Balance under previous accounting policies			Impact on accounting policy change
			NT$000			NT$000			NT$000
Revenue		(a)(d)		18,480,027			18,434,763			45,264
Cost of revenue		(a)(e)		(15,050,032	)		(15,021,266	)		(28,766	)
Operating expenses		(f)		(1,477,788	)		(1,477,653	)		(135	)
Other non-operating income (expenses), net		(g)		173,070			173,476			(406	)
Income tax expense		(c)(h)		(456,618	)		(465,392	)		8,774
Profit for the year				1,325,824			1,301,093			24,731

Earnings per share (in dollars)
Basic			NT$	1.65		NT$	1.62		NT$	0.03
Diluted			NT$	1.63		NT$	1.60		NT$	0.03

Explanation on the adjustments:

Impact on January 1, 2018

(a)

Revenue recognition of customized products

(b)

Presentation of refund liabilities

(c)

Recognition of deferred tax

Impact on December 31, 2018

(d)

Contract assets and revenue recognition

(e)

Transfer inventory to cost of revenue

(f)

Expected credit loss recognition

(g)

Foreign exchange

(h)

Recognition of deferred tax

(i)

Presentation of contract liabilities

(j)

Presentation of refund liabilities

Corporate and Group Information - Additional Information (Detail)	Mar. 31, 2017	Oct. 30, 2016
Disclosure of corporate and group information [Line Items]
Percentage of equity interest held by former parent company, ChipMOS TECHNOLOGIES (Bermuda) LTD.		60.25%
ChipMOS TECHNOLOGIES (Shanghai) LTD. [member]
Disclosure of corporate and group information [Line Items]
Percentage of equity interest in subsidiary sold	54.98%
Percentage of equity interest in subsidiary	45.02%

Basis of Presentation of Financial Statements and Principal Accounting Policies - Additional Information (Detail) $ in Thousands, $ in Thousands	Nov. 01, 2016	Jan. 01, 2019 TWD ($)	Jan. 01, 2019 USD ($)
Certain properties [member]
Disclosure of detailed information about basis of presentation of financial statements and principal accounting policies [line items]
Estimated useful life of individual assets	16 years
Certain equipment [member] \| Bottom of range [member]
Disclosure of detailed information about basis of presentation of financial statements and principal accounting policies [line items]
Estimated useful life of individual assets	2 years
Certain equipment [member] \| Top of range [member]
Disclosure of detailed information about basis of presentation of financial statements and principal accounting policies [line items]
Estimated useful life of individual assets	8 years
Effects of adopting new standards [member]
Disclosure of detailed information about basis of presentation of financial statements and principal accounting policies [line items]
Right-of-use asset		$ 898,387	$ 29,349
Lease liability		884,275	28,888
Lease assets		(31,904)	(1,042)
Lease obligations payable		$ (17,792)	$ (581)

Basis of Preparation of Financial Statements and Principal Accounting Policies - Summary of Ownership Interests in Subsidiaries (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
ChipMOS U.S.A., Inc [member]
Disclosure of joint ventures [line items]
Name of investor	The Company
Main businesses	Research, development and marketing of semiconductors, circuits, and electronic related products
Location	San Jose, USA
Percentage of Ownership (%)	100.00%	100.00%
ChipMOS BVI [member]
Disclosure of joint ventures [line items]
Name of investor	The Company
Main businesses	Holding company
Location	British Virgin Islands
Percentage of Ownership (%)	100.00%	100.00%

Basis of Preparation of Financial Statements and Principal Accounting Policies - Impact on Depreciation Expenses of Current and Future Periods due to Change in Estimated Useful Lives of Certain Properties and Equipment (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2016 TWD ($)
Disclosure of detailed information about property, plant and equipment [Line Items]
Decrease in depreciation expenses	$ (119,737)
Within 1 year [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Decrease in depreciation expenses	(605,259)
1-2 years [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Decrease in depreciation expenses	(391,669)
2-3 years [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Decrease in depreciation expenses	$ (164,863)

Basis of Preparation of Financial Statements and Principal Accounting Policies - Estimated Useful Life for Depreciation of Individual Assets (Detail)	12 Months Ended
	Dec. 31, 2018
Buildings [member] \| Bottom of range [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Estimated useful life of individual assets	5 Years
Buildings [member] \| Top of range [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Estimated useful life of individual assets	51 Years
Machinery and equipment [member] \| Bottom of range [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Estimated useful life of individual assets	2 Years
Machinery and equipment [member] \| Top of range [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Estimated useful life of individual assets	8 Years
Tools [member] \| Bottom of range [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Estimated useful life of individual assets	2 Years
Tools [member] \| Top of range [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Estimated useful life of individual assets	4 Years
Other equipment [member] \| Bottom of range [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Estimated useful life of individual assets	2 Years
Other equipment [member] \| Top of range [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Estimated useful life of individual assets	6 Years

Segment Information - Financial Segment Information for Operating Segments (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)	Dec. 31, 2016 TWD ($)
Revenue
Revenue	$ 18,480,027	$ 603,725	$ 17,940,855	$ 18,387,593
Operating profit (loss)	2,099,721	68,596	2,239,881	1,998,575
Interest expense	(152,416)	(4,979)	(190,425)	(144,545)
Share of profit (loss) of associates	(300,101)	(9,804)	(179,491)	28,924
Purchase of property, plant and equipment	4,945,570	161,567	4,702,691
Continuing operations [member]
Revenue
Revenue	18,480,027	603,725	17,940,855	18,387,593
Operating profit (loss)	2,099,721	68,596	2,239,881	1,998,575
Depreciation expenses	(3,376,579)	(110,310)	(2,899,278)	(3,089,904)
Interest income	49,971	1,633	53,123	38,554
Interest expense	(152,416)	(4,979)	(190,425)	(144,545)
Share of profit (loss) of associates	(300,101)	(9,804)	(179,491)	28,924
Purchase of property, plant and equipment	4,945,570	161,567	4,702,691	3,123,312
Continuing operations [member] \| External [member]
Revenue
Revenue	18,480,027	603,725	17,940,855	18,387,593
Continuing operations [member] \| Goods or services transferred over time [member]
Revenue
Revenue	18,480,027	$ 603,725
Continuing operations [member] \| Operating segments [member] \| Testing [member]
Revenue
Revenue	4,790,097		4,838,246	4,587,054
Operating profit (loss)	1,306,742		1,448,939	1,346,874
Depreciation expenses	(769,660)		(673,393)	(664,026)
Purchase of property, plant and equipment	1,563,919		836,894	771,500
Continuing operations [member] \| Operating segments [member] \| Testing [member] \| External [member]
Revenue
Revenue	4,790,097		4,838,246	4,587,054
Continuing operations [member] \| Operating segments [member] \| Testing [member] \| Goods or services transferred over time [member]
Revenue
Revenue	4,790,097
Continuing operations [member] \| Operating segments [member] \| Assembly [member]
Revenue
Revenue	4,679,676		5,259,281	5,881,883
Operating profit (loss)	(207,700)		(55,198)	143,220
Depreciation expenses	(578,205)		(597,500)	(635,481)
Purchase of property, plant and equipment	321,976		655,879	554,162
Continuing operations [member] \| Operating segments [member] \| Assembly [member] \| External [member]
Revenue
Revenue	4,679,676		5,259,281	5,880,780
Continuing operations [member] \| Operating segments [member] \| Assembly [member] \| Intersegment [member]
Revenue
Revenue				1,103
Continuing operations [member] \| Operating segments [member] \| Assembly [member] \| Goods or services transferred over time [member]
Revenue
Revenue	4,679,676
Continuing operations [member] \| Operating segments [member] \| LCDD [member]
Revenue
Revenue	5,694,720		4,790,116	4,920,302
Operating profit (loss)	1,226,755		1,285,495	963,698
Depreciation expenses	(1,400,784)		(1,048,587)	(1,167,908)
Purchase of property, plant and equipment	2,732,141		2,615,153	910,457
Continuing operations [member] \| Operating segments [member] \| LCDD [member] \| External [member]
Revenue
Revenue	5,694,720		4,789,869	4,920,302
Continuing operations [member] \| Operating segments [member] \| LCDD [member] \| Intersegment [member]
Revenue
Revenue			247
Continuing operations [member] \| Operating segments [member] \| LCDD [member] \| Goods or services transferred over time [member]
Revenue
Revenue	5,694,720
Continuing operations [member] \| Operating segments [member] \| Bumping [member]
Revenue
Revenue	3,315,534		3,053,459	2,999,967
Operating profit (loss)	(202,497)		(336,123)	(341,356)
Depreciation expenses	(627,412)		(579,605)	(622,412)
Purchase of property, plant and equipment	327,251		594,765	887,144
Continuing operations [member] \| Operating segments [member] \| Bumping [member] \| External [member]
Revenue
Revenue	3,315,534		3,053,459	2,999,457
Continuing operations [member] \| Operating segments [member] \| Bumping [member] \| Intersegment [member]
Revenue
Revenue				510
Continuing operations [member] \| Operating segments [member] \| Bumping [member] \| Goods or services transferred over time [member]
Revenue
Revenue	3,315,534
Continuing operations [member] \| Operating segments [member] \| Others [member]
Revenue
Revenue	35,738		35,808	41,670
Operating profit (loss)	(23,433)		(100,545)	(82,331)
Depreciation expenses	(518)		(503)	(565)
Interest income	49,971		53,123	51,756
Interest expense	(152,416)		(190,425)	(144,545)
Share of profit (loss) of associates	(668,377)		1,347,851	(128,866)
Purchase of property, plant and equipment	283			49
Continuing operations [member] \| Operating segments [member] \| Others [member] \| Intersegment [member]
Revenue
Revenue	35,738		35,808	41,670
Continuing operations [member] \| Operating segments [member] \| Others [member] \| Goods or services transferred at point in time [member]
Revenue
Revenue	35,738
Continuing operations [member] \| Elimination [member]
Revenue
Revenue	(35,738)		(36,055)	(43,283)
Operating profit (loss)	(146)		(2,687)	(31,530)
Depreciation expenses			310	488
Interest income				(13,202)
Share of profit (loss) of associates	368,276		(1,527,342)	157,790
Continuing operations [member] \| Elimination [member] \| Intersegment [member]
Revenue
Revenue	(35,738)		(36,055)	(43,283)
Continuing operations [member] \| Elimination [member] \| Goods or services transferred at point in time [member]
Revenue
Revenue	$ (35,738)
Discontinued operations: Unimos Shanghai [member]
Revenue
Revenue			227,095	1,005,166
Operating profit (loss)			(25,394)	(146,263)
Depreciation expenses				(141,375)
Interest income			464	3,753
Interest expense			(2,414)	(606)
Purchase of property, plant and equipment				1,567,683
Discontinued operations: Unimos Shanghai [member] \| External [member]
Revenue
Revenue			$ 227,095	$ 1,005,166

Segment Information - Geographic Information of Revenue (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)	Dec. 31, 2016 TWD ($)
Disclosure of geographical areas [Line Items]
Revenue	$ 18,480,027	$ 603,725	$ 17,940,855	$ 18,387,593
ROC [member]
Disclosure of geographical areas [Line Items]
Revenue	14,751,766	481,926	13,152,419	12,728,014
Japan [member]
Disclosure of geographical areas [Line Items]
Revenue	1,825,479	59,637	2,257,296	1,855,674
Singapore [member]
Disclosure of geographical areas [Line Items]
Revenue	1,143,661	37,362	1,798,585	3,087,835
Others [member]
Disclosure of geographical areas [Line Items]
Revenue	$ 759,121	$ 24,800	$ 732,555	$ 716,070

- Definition

The income arising in the course of an entity's ordinary activities. Income is increases in economic benefits during the accounting period in the form of inflows or enhancements of assets or decreases of liabilities that result in an increase in equity, other than those relating to contributions from equity participants.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 8
-IssueDate 2018-01-01
-Paragraph 28
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=8&date=2018-03-01&anchor=para_28_a&doctype=Standard
-URIDate 2018-03-16

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 8
-IssueDate 2018-01-01
-Paragraph 23
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=8&date=2018-03-01&anchor=para_23_a&doctype=Standard
-URIDate 2018-03-16

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 8
-IssueDate 2018-01-01
-Paragraph 32
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=8&date=2018-03-01&anchor=para_32&doctype=Standard
-URIDate 2018-03-16

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 8
-IssueDate 2018-01-01
-Paragraph 33
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=8&date=2018-03-01&anchor=para_33_a&doctype=Standard
-URIDate 2018-03-16

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 8
-IssueDate 2018-01-01
-Paragraph 34
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=8&date=2018-03-01&anchor=para_34&doctype=Standard
-URIDate 2018-03-16

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2018-01-01
-Paragraph 82
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_82_a&doctype=Standard
-URIDate 2018-03-16

Reference 7: http://www.xbrl.org/2003/role/exampleRef
-Name IAS
-Number 1
-IssueDate 2018-01-01
-Paragraph 103
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_103&doctype=Standard
-URIDate 2018-03-16

Reference 8: http://www.xbrl.org/2003/role/exampleRef
-Name IAS
-Number 1
-IssueDate 2018-01-01
-Paragraph 102
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_102&doctype=Standard
-URIDate 2018-03-16

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 5
-IssueDate 2018-01-01
-Paragraph 33
-Subparagraph b
-Clause i
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=5&date=2018-03-01&anchor=para_33_b_i&doctype=Standard
-URIDate 2018-03-16

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2018-01-01
-Paragraph B12
-Subparagraph b
-Clause v
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=12&date=2018-03-01&anchor=para_B12_b_v&doctype=Appendix&seq=2
-URIDate 2018-03-16

Reference 11: http://www.xbrl.org/2003/role/exampleRef
-Name IFRS
-Number 12
-IssueDate 2018-01-01
-Paragraph B10
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=12&date=2018-03-01&anchor=para_B10_b&doctype=Appendix&seq=2
-URIDate 2018-03-16

+ Details

Segment Information - Net Revenue from Customers Representing at Least 10% of Total Revenue (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)	Dec. 31, 2016 TWD ($)
Disclosure of major customers [Line Items]
Net revenue	$ 18,480,027	$ 603,725	$ 17,940,855	$ 18,387,593
Customer A [member]
Disclosure of major customers [Line Items]
Net revenue	$ 3,794,991	$ 123,979	$ 3,434,873	$ 3,370,285
Percentage of total revenue	21.00%	21.00%	19.00%	18.00%
Customer K [member]
Disclosure of major customers [Line Items]
Net revenue	$ 2,637,053	$ 86,150	$ 2,742,882	$ 2,633,431
Percentage of total revenue	14.00%	14.00%	15.00%	14.00%
Customer C [member]
Disclosure of major customers [Line Items]
Net revenue	$ 1,957,467	$ 63,949	$ 1,530,209	$ 1,870,675
Percentage of total revenue	11.00%	11.00%	9.00%	10.00%
Customer I [member]
Disclosure of major customers [Line Items]
Net revenue	$ 1,101,956	$ 36,000	$ 1,798,111	$ 3,085,190
Percentage of total revenue	6.00%	6.00%	10.00%	17.00%

- Definition

+ References

+ Details

Segment Information - Summary of Contract Assets and Liabilities (Detail) - Dec. 31, 2018 $ in Thousands, $ in Thousands	TWD ($)	USD ($)
Disclosure of major customers [abstract]
Contract assets	$ 299,835	$ 9,795
Contract liabilities (Advance payments)	$ 1,432	$ 47

Operating Costs and Expenses - Summary of Operating Costs and Expenses (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)	Dec. 31, 2016 TWD ($)
Analysis of income and expense [abstract]
Change of finished goods and work in process			$ 31,977	$ (19,498)
Consumption of raw materials and supplies	$ 3,079,909	$ 100,617	3,036,350	3,346,540
Employee benefit expenses	5,606,833	183,170	5,895,778	5,317,125
Depreciation and amortization	3,376,579	110,310	2,899,278	3,089,904
Other expenses	4,464,499	145,851	4,530,425	4,745,253
Total operating costs and expenses	16,527,820	539,948	16,393,808	16,479,324
Employee benefit expenses
Salaries	4,628,039	151,194	4,847,433	4,109,393
Directors remuneration	18,456	603	27,276	16,810
Labor and health insurance	406,111	13,267	390,788	351,232
Pension	201,567	6,585	198,502	183,293
Share-based payments	41,043	1,341	123,021	356,463
Other personnel expenses	311,617	10,180	308,758	299,934
Total employee benefit costs	$ 5,606,833	$ 183,170	$ 5,895,778	$ 5,317,125

Other Operating Income (Expenses), Net - Summary of Other Operating Income (Expenses), Net (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)	Dec. 31, 2016 TWD ($)
Analysis of income and expense [abstract]
Gain on disposal of property, plant and equipment, net	$ 14,274	$ 466	$ 132,777	$ 2,575
Impairment on property, plant and equipment			(956)	(8,198)
Gain on disposal of scrapped materials	59,380	1,940	27,940	30,476
Gain on disposal of items purchased on behalf of others	31,268	1,021	26,417	48,812
Royalty income	43,224	1,412	11,998
Insurance compensation income	147	5	486,858	7,033
Others	(779)	(25)	7,800	9,608
Other operating income (expenses), net	$ 147,514	$ 4,819	$ 692,834	$ 90,306

Finance Costs - Summary of Finance Costs (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)	Dec. 31, 2016 TWD ($)
Analysis of Finance Costs [abstract]
Bank loans	$ 170,476	$ 5,569	$ 208,486	$ 157,254
Lease obligations payable	482	16	708	212
Less: Amounts capitalized in qualifying assets	(18,542)	(606)	(18,769)	(12,921)
Interest expense	152,416	4,979	190,425	144,545
Finance expense	37,832	1,236	26,858	34,571
Finance costs	$ 190,248	$ 6,215	$ 217,283	$ 179,116

Other Non-operating Income (Expenses), Net - Summary of Other Non-operating Income (Expenses), Net (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)	Dec. 31, 2016 TWD ($)
Analysis of other non-operating income and expense [abstract]
Bank deposits	$ 49,051	$ 1,603	$ 53,123	$ 38,554
Financial assets at amortized cost	920	30
Foreign exchange gains (losses), net	93,104	3,041	(418,970)	(195,326)
Gain on valuation of financial assets at fair value through profit or loss	1,485	49	637	621
Gain on disposal of long-term investment in associates			16,929
Rental income	7,819	255	11,075	8,203
Dividend income	571	19
Reimbursement of ADSs service charge	13,269	433	23,707
Others	6,851	224	2,808
Other non-operating income (expenses), net	$ 173,070	$ 5,654	$ (310,691)	$ (147,948)

Income Tax Expense - Additional Information (Detail) $ in Thousands, $ in Thousands		12 Months Ended
	Jan. 01, 2018	Dec. 31, 2017 TWD ($)	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)
Disclosure of income tax expense [Line Items]
Deductible temporary differences		$ 28,584	$ 0	$ 0
Taxable temporary differences		$ 920,943	$ 495,154	$ 16,176
Profit seeking enterprise [member]
Disclosure of income tax expense [Line Items]
Statutory tax rates	20.00%	17.00%
unappropriated retained earnings tax rate	5.00%	10.00%

Income Tax Expense - Major Components of Income Tax Expense (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)	Dec. 31, 2016 TWD ($)
Current income tax:
Current income tax on profits for the period	$ 326,057	$ 10,652	$ 125,376	$ 331,144
Income tax (benefit) on unappropriated retained earnings	28,165	920	246,684	(174,930)
Prior year income tax under estimation	3,729	122	67,885	4,527
Total current income tax	357,951	11,694	439,945	160,741
Deferred income tax:
Relating to origination and reversal of temporary differences	101,441	3,314	110,542	16,379
Impact of change in tax rate	(2,774)	(90)
Total deferred income tax	98,667	3,224	110,542	16,379
Income tax expense reported in the consolidated statements of comprehensive income	$ 456,618	$ 14,918	$ 550,487	$ 177,120

Income Tax Expense - Deferred Tax Charged to Other Comprehensive Income (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)	Dec. 31, 2016 TWD ($)
Income tax relating to components of other comprehensive income [abstract]
Unrealized gain on valuation of financial assets at fair value through other comprehensive income	$ 17,005	$ 556
Remeasurement of defined benefit obligations	(11,992)	(392)	$ 8,642	$ (7,375)
Impact of change in tax rate	(887)	(29)
Total	$ 4,126	$ 135	$ 8,642	$ (7,375)

Income Tax Expense - Reconciliation of Income Tax Expense and Accounting Profit Before Income Tax (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)	Dec. 31, 2016 TWD ($)
Reconciliation of income tax expense and accounting profit before income tax [abstract]
Tax calculated based on profit before tax and statutory tax rate	$ 356,488	$ 11,646	$ 566,649	$ 214,550
Expenses disallowed (added) by tax regulations	14,689	480	10,185	(2,190)
Temporary difference not recognized as deferred tax assets	(10,951)	(358)	(85,168)	1,306
Tax exempted (income) expenses by tax regulation	66,353	2,168	(256,788)	12,057
Taxable loss not recognized as deferred tax assets				54,012
Effect of different tax rates in countries in which the Group operates	919	30	1,040	10,451
Withholding tax				57,337
Impact of change in tax rate	(2,774)	(90)
Prior year income tax under estimation	3,729	122	67,885	4,527
Income tax (benefit) on unappropriated retained earnings	28,165	920	246,684	(174,930)
Income tax expense reported in the consolidated statements of comprehensive income	$ 456,618	$ 14,918	$ 550,487	$ 177,120

Income Tax Expense - Details of Deferred Tax Assets (Liabilities) (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)	Dec. 31, 2016 TWD ($)
Disclosure of the detail of deferred tax assets and liabilities [line items]
Profit or loss	$ (98,667)	$ (3,224)	$ (110,542)	$ (16,379)
Unrealized exchange losses deferred tax assets [member]
Disclosure of the detail of deferred tax assets and liabilities [line items]
Beginning balance	8,167
Retroactive adjustment	144
Profit or loss	(4,736)		8,167
Ending balance	3,575	117	8,167
Deferred tax assets unrealized loss on inventories [member]
Disclosure of the detail of deferred tax assets and liabilities [line items]
Beginning balance	9,132		26,324
Retroactive adjustment	(770)
Profit or loss	(1,130)		(17,192)
Ending balance	7,232	236	9,132	26,324
Property, plant and equipment, deferred tax assets [member]
Disclosure of the detail of deferred tax assets and liabilities [line items]
Beginning balance	55,494		80,869
Profit or loss	8,689		(25,375)
Ending balance	64,183	2,097	55,494	80,869
Deferred tax assets deferred revenue [member]
Disclosure of the detail of deferred tax assets and liabilities [line items]
Beginning balance	39,485		41,294
Profit or loss	(5,329)		(1,809)
Ending balance	34,156	1,116	39,485	41,294
Provisions [member]
Disclosure of the detail of deferred tax assets and liabilities [line items]
Beginning balance	21,643		11,232
Profit or loss	(9,247)		10,411
Ending balance	12,396	405	21,643	11,232
Net defined benefit liability [member]
Disclosure of the detail of deferred tax assets and liabilities [line items]
Beginning balance	78,451		90,087
Profit or loss	7,889		(2,994)
Other comprehensive income	14,403		(8,642)
Ending balance	100,743	3,291	78,451	90,087
Deferred tax asset [member]
Disclosure of the detail of deferred tax assets and liabilities [line items]
Beginning balance	212,372		249,806
Retroactive adjustment	(626)
Profit or loss	567		(28,792)
Other comprehensive income	14,403		(8,642)
Ending balance	226,716	7,407	212,372	249,806
Unrealised exchange gains (losses), deferred tax liabilities [member]
Disclosure of the detail of deferred tax assets and liabilities [line items]
Beginning balance			(14,155)
Profit or loss			14,155
Ending balance				(14,155)
Property, plant and equipment, deferred tax liabilities [member]
Disclosure of the detail of deferred tax assets and liabilities [line items]
Beginning balance	(174,293)		(78,388)
Profit or loss	(107,301)		(95,905)
Ending balance	(281,594)	(9,200)	(174,293)	(78,388)
Deferred tax liabilities [member]
Disclosure of the detail of deferred tax assets and liabilities [line items]
Beginning balance	(174,293)		(92,543)
Retroactive adjustment	(16,703)
Profit or loss	(99,234)		(81,750)
Other comprehensive income	(18,529)
Ending balance	(308,759)	(10,087)	$ (174,293)	$ (92,543)
Investment tax credit [member]
Disclosure of the detail of deferred tax assets and liabilities [line items]
Profit or loss	4,420
Ending balance	4,420	144
Other [member]
Disclosure of the detail of deferred tax assets and liabilities [line items]
Profit or loss	11
Ending balance	11	1
Deferred tax liabilities, contract assets [member]
Disclosure of the detail of deferred tax assets and liabilities [line items]
Retroactive adjustment	(8,067)
Profit or loss	8,067
Financial assets at fair value through other comprehensive income [member]
Disclosure of the detail of deferred tax assets and liabilities [line items]
Retroactive adjustment	(8,636)
Other comprehensive income	(18,529)
Ending balance	$ (27,165)	$ (887)

Earnings Per Share ("EPS") - Income and Share Data Used in Basic and Diluted EPS Computations (Detail) $ / shares in Units, $ / shares in Units, shares in Thousands, $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018 TWD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 TWD ($) $ / shares shares	Dec. 31, 2016 TWD ($) $ / shares shares
Basic earnings per share, amount after tax
Equity holders of the Company - Continuing operations, amount after tax	$ 1,325,824	$ 43,313	$ 981,929	$ 1,829,327
Equity holders of the Company - Discontinued operations, amount after tax			1,814,953	(122,105)
Equity holders of the Company, amount after tax	1,325,824		2,796,882	1,707,222
Predecessors' interests, amount after tax				(306,012)
Profit (loss) attributable to equity holders of the Company, amount after tax				1,401,210
Diluted earnings per share, amount after tax
Equity holders of the Company - Continuing operations, amount after tax	1,325,824	$ 43,313	981,929	1,829,327
Equity holders of the Company - Discontinued operations, amount after tax			1,814,953	(122,105)
Equity holders of the Company, amount after tax	$ 1,325,824		$ 2,796,882	1,707,222
Predecessors' interests, amount after tax				(306,012)
Profit (loss) attributable to equity holders of the Company, amount after tax				$ 1,401,210
Weighted-average number of ordinary shares outstanding \| shares	802,725	802,725	846,686	859,644
Employees' compensations \| shares	7,626	7,626	14,034	3,035
Restricted shares \| shares	3,356	3,356	5,075	4,122
Weighted-average number of ordinary shares outstanding \| shares	813,707	813,707	865,795	866,801
Ordinary shares [member]
Basic earnings per share, amount after tax
Diluted earnings per share \| (per share)	$ 1.63	$ 0.05	$ 3.23	$ 1.97
Basic earnings per share
Equity holders of the Company - Continuing operations, earnings per share \| (per share)	1.65	0.05	1.16	2.13
Equity holders of the Company - Discontinued operations, earnings per share \| $ / shares			2.14	(0.14)
Equity holders of the Company - Earnings per share \| (per share)	1.65	0.05	3.30	1.99
Predecessors' interests, earnings per share \| $ / shares				(0.35)
Basic earnings per share \| (per share)	1.65	0.05	3.30	1.64
Diluted earnings per share
Equity holders of the Company - Continuing operations, earnings per share \| (per share)	1.63	0.05	1.13	2.11
Equity holders of the Company - Discontinued operations, earnings per share \| $ / shares			2.10	(0.14)
Equity holders of the Company - Earnings per share \| (per share)	1.63	0.05	3.23	1.97
Predecessors' interests, earnings per share \| $ / shares				(0.35)
Diluted earnings per share \| (per share)	$ 1.63	$ 0.05	$ 3.23	$ 1.62

Non-current Financial Assets at Fair Value Through Profit or Loss - Non-current - Summary of Non-current Financial Assets at Fair Value Through Profit or Loss (Detail) - Dec. 31, 2018 $ in Thousands, $ in Thousands	TWD ($)	USD ($)
Financial Assets At Fair Value Through Profit Or Loss [line items]
Financial assets mandatorily measured at fair value through profit or loss	$ 11,471	$ 375
Foreign partnership interest [member]
Financial Assets At Fair Value Through Profit Or Loss [line items]
Financial assets mandatorily measured at fair value through profit or loss	10,940	358
Valuation adjustments [member]
Financial Assets At Fair Value Through Profit Or Loss [line items]
Financial assets mandatorily measured at fair value through profit or loss	$ 531	$ 17

Non-current Financial Assets at Fair Value Through Profit or Loss - Non-current - Summary of Amounts recognized in Profit or Loss in Relation to Financial Assets at Fair Value Through Profit or Loss (Detail) - Dec. 31, 2018 $ in Thousands, $ in Thousands	TWD ($)	USD ($)
Financial Assets At Fair Value Through Profit Or Loss [line items]
Financial assets mandatorily measured at fair value through profit or loss	$ 1,485	$ 49
Foreign partnership interest [member]
Financial Assets At Fair Value Through Profit Or Loss [line items]
Financial assets mandatorily measured at fair value through profit or loss	38	1
Beneficiary certificates [member]
Financial Assets At Fair Value Through Profit Or Loss [line items]
Financial assets mandatorily measured at fair value through profit or loss	1,396	46
Derivative instrument [member]
Financial Assets At Fair Value Through Profit Or Loss [line items]
Financial assets mandatorily measured at fair value through profit or loss	$ 51	$ 2

Non-current Financial Assets at Fair Value Through Other Comprehensive Income - Summary of Non-current Financial Assets at Fair Value Through Other Comprehensive Income (Detail) - Dec. 31, 2018 $ in Thousands, $ in Thousands	TWD ($)	USD ($)
Financial assets at fair value through other comprehensive income [line items]
Designation of equity instruments	$ 174,357	$ 5,696
Foreign unlisted stocks [member]
Financial assets at fair value through other comprehensive income [line items]
Designation of equity instruments	38,534	1,259
Valuation adjustments [member]
Financial assets at fair value through other comprehensive income [line items]
Designation of equity instruments	$ 135,823	$ 4,437

Non-current Financial Assets at Fair Value Through Other Comprehensive Income - Additional Information (Detail) - 12 months ended Dec. 31, 2018 $ in Thousands	TWD ($)	USD ($)	USD ($)
Financial assets at fair value through other comprehensive income [abstract]
Designation of equity instruments	$ 174,357,000		$ 5,696
Dividend income recognized	571,000	$ 19
Financial assets at fair value through other comprehensive income were pledged	$ 0

Investment in Associates - Details of Investment in Associates (Detail) $ in Thousands, $ in Thousands	1 Months Ended	12 Months Ended
	Jan. 31, 2017	Dec. 31, 2018 TWD ($)	Dec. 31, 2017 TWD ($)	Dec. 31, 2016	Dec. 31, 2018 USD ($)
Disclosure of associates [line items]
Carrying amount		$ 3,863,741	$ 3,433,332		$ 126,225
JMC ELECTRONICS CO., LTD. [member]
Disclosure of associates [line items]
Country of incorporation and business			Kaohsiung, Taiwan
Measurement method			Equity method
Carrying amount		$ 406,792	$ 373,276		13,290
Ownership	19.10%	19.10%	19.10%	21.22%
Unimos Shanghai [member]
Disclosure of associates [line items]
Country of incorporation and business			Shanghai, People's Republic of China
Measurement method			Equity method
Carrying amount		$ 3,456,949	$ 3,060,056		$ 112,935
Ownership		45.02%	45.02%

Investment in Associates - Additional Information (Detail) $ in Thousands, $ in Thousands	1 Months Ended				12 Months Ended
	Jan. 31, 2018 TWD ($)	Jan. 31, 2018 USD ($)	Jun. 30, 2017 TWD ($)	Jan. 31, 2017	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)	Dec. 31, 2016	Mar. 31, 2017
Disclosure of associates [line items]
Acquisition of investment in associate					$ 794,694	$ 25,962	$ 1,373,486
Share of profit (loss) of investment associates					$ (300,101)	$ (9,804)	$ (179,491)
JMC ELECTRONICS CO., LTD. [member]
Disclosure of associates [line items]
Percentage of ownership interest in associate				19.10%	19.10%	19.10%	19.10%	21.22%
Disposal gain from long-term investment							$ 16,929
Unimos Shanghai [member]
Disclosure of associates [line items]
Sale of equity percentage									54.98%
Percentage of ownership interest in associate					45.02%	45.02%	45.02%
Acquisition of investment in associate	$ 794,694	$ 25,962	$ 1,373,486

Investment in Associates - Summarized Financial Information for Investment in Material Associates (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)	Dec. 31, 2016 TWD ($)	Dec. 31, 2018 USD ($)
Disclosure of associates [line items]
Current assets	$ 11,888,143		$ 14,200,980		$ 388,375
Non-current assets	21,245,575		19,058,962		694,073
Current liabilities	(5,239,833)		(6,942,995)		(171,181)
Non-current liabilities	(9,872,712)		(8,195,998)		(322,532)
Carrying amount	3,863,741		3,433,332		126,225
Revenue	18,480,027	$ 603,725	17,940,855	$ 18,387,593
Profit (loss) for the year from continuing operations	1,325,824	43,313	981,929	1,523,315
Other comprehensive income (loss), net of income tax	(32,829)	(1,072)	(189,902)	(236,421)
Total comprehensive income (loss)	1,292,995	42,241	2,606,980	1,164,789
Unimos Shanghai [member]
Disclosure of associates [line items]
Current assets	3,946,082		3,380,641		128,915
Non-current assets	3,254,687		2,766,839		106,328
Current liabilities	(554,160)		(460,054)		(18,104)
Non-current liabilities	(442,306)		(489,097)		(14,450)
Total net assets	6,204,303		5,198,329		202,689
Group's share	2,793,438		2,340,506		91,259
Depreciable assets	644,718		703,536		21,062
Goodwill	22,118		22,118		723
Inter-company transactions and amortization	(3,325)		(6,104)		(109)
Carrying amount	3,456,949		3,060,056		112,935
Revenue	1,334,196	43,587	1,141,415
Profit (loss) for the year from continuing operations	(629,303)	(20,559)	(348,472)
Total comprehensive income (loss)	(629,303)	(20,559)	(348,472)
JMC ELECTRONICS CO., LTD. [member]
Disclosure of associates [line items]
Current assets	1,106,789		843,636		36,158
Non-current assets	1,699,498		1,161,620		55,521
Current liabilities	(817,697)		(294,302)		(26,714)
Non-current liabilities	(103,922)		(1,756)		(3,395)
Total net assets	1,884,668		1,709,198		61,570
Group's share	359,972		326,456		11,760
Goodwill	46,820		46,820		1,530
Carrying amount	406,792		373,276		$ 13,290
Revenue	1,931,008	63,084	1,322,928	1,667,761
Profit (loss) for the year from continuing operations	219,544	7,172	4,414	136,303
Other comprehensive income (loss), net of income tax	(14,074)	(460)	2,903	(627)
Total comprehensive income (loss)	205,470	6,712	7,317	135,676
Dividend received from the associate	$ 5,730	$ 187	$ 14,325	$ 5,730

Financial Assets at Amortized Cost - Schedule of Income from Financial Assets at Amortized Cost (Detail) - 12 months ended Dec. 31, 2018 $ in Thousands, $ in Thousands	TWD ($)	USD ($)	USD ($)
Financial Instruments At Amortised Cost Category[abstract]
Time deposits	$ 169,168		$ 5,526
Time deposits	30,715		1,003
Restricted bank deposits	68,388		2,234
Non-current financial assets at amortized cost	99,103		$ 3,237
Interest income	$ 920	$ 30

Property, Plant and Equipment, Net - Summary of Property, Plant and Equipment, Net (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)	Dec. 31, 2016 TWD ($)
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning Balance			$ 15,531,186
Less: Property, plant and equipment classified as held for sale			(2,033,968)
Beginning Balance	$ 15,265,311	$ 498,704	13,497,218
Additions	4,945,570	161,567	4,702,691
Disposals	(14,716)	(481)	(34,233)
Depreciation expenses	(3,376,579)	(110,310)	(2,899,278)
Impairment losses			(956)	$ (8,198)
Exchange adjustments	35	1	(131)
Ending Balance	16,819,621	549,481	15,265,311	13,497,218
Land [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning Balance			452,738
Beginning Balance	452,738		452,738
Ending Balance	452,738		452,738	452,738
Buildings [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning Balance			4,787,946
Less: Property, plant and equipment classified as held for sale			(710,191)
Beginning Balance	3,919,086		4,077,755
Additions	247,186		211,098
Reclassifications	199,724		141,400
Depreciation expenses	(457,265)		(511,167)
Ending Balance	3,908,731		3,919,086	4,077,755
Machinery and equipment [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning Balance			7,571,620
Less: Property, plant and equipment classified as held for sale			(433,688)
Beginning Balance	8,813,727		7,137,932
Additions	2,445,313		2,007,767
Disposals	(904)		(30,066)
Reclassifications	1,154,663		1,535,619
Depreciation expenses	(2,180,718)		(1,837,482)
Exchange adjustments	12		(43)
Ending Balance	10,232,093		8,813,727	7,137,932
Tools [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning Balance			524,443
Less: Property, plant and equipment classified as held for sale			(90,460)
Beginning Balance	690,469		433,983
Additions	591,229		571,601
Disposals	(11,745)		(2,302)
Reclassifications	7,604		44,882
Depreciation expenses	(535,378)		(357,695)
Ending Balance	742,179		690,469	433,983
Other equipment [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning Balance			566,623
Less: Property, plant and equipment classified as held for sale			(168,314)
Beginning Balance	420,572		398,309
Additions	172,652		195,957
Disposals	(2,067)		(1,865)
Reclassifications	26,026		22,149
Depreciation expenses	(203,218)		(192,934)
Impairment losses			(956)
Exchange adjustments	23		(88)
Ending Balance	413,988		420,572	398,309
Construction in progress and equipment to be inspected [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning Balance			1,627,816
Less: Property, plant and equipment classified as held for sale			(631,315)
Beginning Balance	968,719		996,501
Additions	1,489,190		1,716,268
Reclassifications	(1,388,017)		(1,744,050)
Ending Balance	1,069,892		968,719	$ 996,501
Gross carrying amount [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning Balance			67,619,367
Beginning Balance	63,638,420	2,079,008
Ending Balance	67,064,936	2,190,948	63,638,420
Gross carrying amount [member] \| Land [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning Balance			452,738
Beginning Balance	452,738
Ending Balance	452,738		452,738
Gross carrying amount [member] \| Buildings [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning Balance			11,183,278
Beginning Balance	9,809,970
Ending Balance	10,254,531		9,809,970
Gross carrying amount [member] \| Machinery and equipment [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning Balance			47,002,228
Beginning Balance	45,778,207
Ending Balance	48,274,171		45,778,207
Gross carrying amount [member] \| Tools [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning Balance			3,999,894
Beginning Balance	4,004,703
Ending Balance	4,402,711		4,004,703
Gross carrying amount [member] \| Other equipment [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning Balance			3,353,413
Beginning Balance	2,624,083
Ending Balance	2,610,893		2,624,083
Gross carrying amount [member] \| Construction in progress and equipment to be inspected [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning Balance			1,627,816
Beginning Balance	968,719
Ending Balance	1,069,892		968,719
Accumulated depreciation and impairment [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning Balance			(52,088,181)
Beginning Balance	(48,373,109)	(1,580,304)
Ending Balance	(50,245,315)	$ (1,641,467)	(48,373,109)
Accumulated depreciation and impairment [member] \| Buildings [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning Balance			(6,395,332)
Beginning Balance	(5,890,884)
Ending Balance	(6,345,800)		(5,890,884)
Accumulated depreciation and impairment [member] \| Machinery and equipment [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning Balance			(39,430,608)
Beginning Balance	(36,964,480)
Ending Balance	(38,042,078)		(36,964,480)
Accumulated depreciation and impairment [member] \| Tools [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning Balance			(3,475,451)
Beginning Balance	(3,314,234)
Ending Balance	(3,660,532)		(3,314,234)
Accumulated depreciation and impairment [member] \| Other equipment [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning Balance			(2,786,790)
Beginning Balance	(2,203,511)
Ending Balance	$ (2,196,905)		$ (2,203,511)

Property, Plant and Equipment, Net - Capitalization Interest and Capitalization Interest Rate Applied Related to Property, Plant and Equipment (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)
Disclosure of detailed information about property, plant and equipment [abstract]
Capitalization interest	$ 18,542	$ 606	$ 18,769
Capitalization interest rate applied	1.7582%	1.7582%	1.7624%

Inventories - Summary of Inventories (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)
Disclosure of inventories [Line Items]
Raw materials	$ 1,778,835	$ 58,113	$ 1,720,734
Work in process			176,089
Finished goods			32,416
Inventories	1,778,835	$ 58,113	1,929,239
Gross carrying amount [member]
Disclosure of inventories [Line Items]
Raw materials	1,814,992		1,769,917
Work in process			180,252
Finished goods			32,784
Inventories			1,982,953
Allowance for impairment losses [member]
Disclosure of inventories [Line Items]
Raw materials	$ (36,157)		(49,183)
Work in process			(4,163)
Finished goods			(368)
Inventories			$ (53,714)

Inventories - Cost of Inventories Recognized as an Expense (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)	Dec. 31, 2016 TWD ($)
Analysis of income and expense [abstract]
Cost of revenue	$ 15,057,605	$ 491,918	$ 14,766,555
Loss on abandonment	5,497	179	38,301
Reversal of inventory valuation and obsolescence loss	(13,070)	(427)	(101,127)
Cost of revenue	$ 15,050,032	$ 491,670	$ 14,703,729	$ 14,745,472

Accounts and Notes and Other Receivables - Summary of Accounts and Notes and Other Receivables (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)
Disclosure of financial assets [Line Items]
Accounts and notes receivable	$ 4,747,288	$ 155,090	$ 4,015,734
Other receivables	63,037	2,059	56,716
Accounts and notes and other receivables	4,810,325	157,149	4,072,450
Accounts receivable [member]
Disclosure of financial assets [Line Items]
Accounts and notes receivable	4,747,834	155,108	4,013,705
Gross carrying amount [member]
Disclosure of financial assets [Line Items]
Other receivables	63,049	2,060	56,716
Gross carrying amount [member] \| Accounts receivable [member]
Disclosure of financial assets [Line Items]
Accounts and notes receivable	4,747,834	155,108	4,013,705
Gross carrying amount [member] \| Notes receivable [member]
Disclosure of financial assets [Line Items]
Accounts and notes receivable	1,595	52	$ 2,029
Loss allowance [member]
Disclosure of financial assets [Line Items]
Accounts and notes receivable	(2,141)	(70)
Loss allowance [member]
Disclosure of financial assets [Line Items]
Other receivables	$ (12)	$ (1)

Accounts and Notes and Other Receivables - Aging of Accounts Receivable which are Past Due but not Impaired (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)
Disclosure of financial assets [Line Items]
Accounts and notes receivable	$ 4,747,288	$ 155,090	$ 4,015,734
Accounts receivable [member]
Disclosure of financial assets [Line Items]
Accounts and notes receivable	4,747,834	155,108	4,013,705
Accounts receivable [member] \| Current [member]
Disclosure of financial assets [Line Items]
Accounts and notes receivable	4,595,300	150,124	3,997,833
Accounts receivable [member] \| Within 1 month [member]
Disclosure of financial assets [Line Items]
Accounts and notes receivable	18,807	615	10,482
Accounts receivable [member] \| 1 - 2 months [member]
Disclosure of financial assets [Line Items]
Accounts and notes receivable	131,787	4,305	477
Accounts receivable [member] \| 2 - 3 months [member]
Disclosure of financial assets [Line Items]
Accounts and notes receivable	1,436	47	426
Accounts receivable [member] \| 3 - 4 months [member]
Disclosure of financial assets [Line Items]
Accounts and notes receivable	180	6	1,431
Accounts receivable [member] \| Over 4 months [member]
Disclosure of financial assets [Line Items]
Accounts and notes receivable	$ 324	$ 11	$ 3,056

Cash and Cash Equivalents - Summary of Cash and Cash Equivalents (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)
Cash and cash equivalents [abstract]
Short-term deposits	$ 3,245,750	$ 106,036	$ 3,883,614
Cash	470	15	470
Cash at banks	1,396,302	45,616	4,151,630
Cash and cash equivalents	$ 4,642,522	$ 151,667	$ 8,035,714

Non-current Assets Held for Sale and Discontinued Operations - Additional Information (Detail) $ in Thousands	1 Months Ended
	Mar. 31, 2017 TWD ($)
Noncurrent assets or disposal groups classified as held for sale or as held for distribution to owners [Line Items]
Cash consideration	$ 2,230,544
Gain on disposal of discontinued operation	$ 1,843,234
Percentage of disposal of equity interest	54.98%
Fair value of gain on disposal of equity interest	$ 999,630
Percentage of fair value gain on remeasurement of retained investment	45.02%
Fair value of gain on remeasurement of retained investment	$ 843,604
Unimos Shanghai [member]
Noncurrent assets or disposal groups classified as held for sale or as held for distribution to owners [Line Items]
Equity interest in subsidiary to be sold	54.98%

Non-current Assets Held for Sale and Discontinued Operations - Cash Flow Information of Discontinued Operations (Detail) - TWD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Non-current assets or disposal groups classified as held for sale or as held for distribution to owners [abstract]
Net cash used in operating activities	$ (109,079)	$ (1,109,029)
Net cash used in investing activities	(272,925)	(1,331,564)
Net cash generated from financing activities	461,312	1,463,664
Effect of foreign exchange rate changes	(19,874)	(61,336)
Net increase (decrease) in cash and cash equivalents	$ 59,434	$ (1,038,265)

Non-current Assets Held for Sale and Discontinued Operations - Results of Discontinued Operations (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)	Dec. 31, 2016 TWD ($)
Noncurrent assets or disposal groups classified as held for sale or as held for distribution to owners [Line Items]
Revenue	$ 18,480,027	$ 603,725	$ 17,940,855	$ 18,387,593
Cost of revenue	(15,050,032)	(491,670)	(14,703,729)	(14,745,472)
Other operating income (expenses), net	147,514	4,819	692,834	90,306
Loss from discontinued operations after income tax	$ (1,782,442)	$ (58,231)	(1,532,416)	(1,700,435)
Profit (loss) from discontinued operations			1,814,953	(122,105)
Discontinued operations: Unimos Shanghai [member]
Noncurrent assets or disposal groups classified as held for sale or as held for distribution to owners [Line Items]
Revenue			227,095	1,005,166
Cost of revenue			(195,078)	(986,004)
Operating expenses			(58,840)	(179,178)
Other operating income (expenses), net			1,429	13,753
Non-operating income (expenses), net			(2,887)	24,158
Loss from discontinued operations after income tax			(28,281)	(122,105)
Income tax expense			0	0
Loss from discontinued operations after income tax			(28,281)	(122,105)
Gain on disposal of discontinued operations			1,843,234
Profit (loss) from discontinued operations			$ 1,814,953	$ (122,105)

Issued Capital - Summary of Issued Capital (Detail) shares in Thousands, $ in Thousands, $ in Thousands	Dec. 31, 2018 TWD ($) shares	Dec. 31, 2018 USD ($) shares	Dec. 31, 2017 TWD ($) shares	Dec. 31, 2016 TWD ($) shares
Disclosure of classes of share capital [abstract]
Authorized shares, Ordinary shares	970,000	970,000	970,000	1,450,000
Ordinary shares	752,858	752,858	886,297	886,966
Issued capital	$ 7,528,577	$ 245,952	$ 8,862,971	$ 8,869,663

Issued Capital - Additional Information (Detail) $ / shares in Units, $ in Thousands, $ in Thousands				12 Months Ended
	Aug. 15, 2018 TWD ($) shares	Aug. 15, 2018 USD ($) shares	Oct. 31, 2016 shares	Dec. 31, 2018 $ / shares shares	Dec. 31, 2017 shares	Dec. 31, 2016 shares	May 12, 2016 TWD ($)	Feb. 04, 2016 TWD ($)	Dec. 31, 2015 shares
Disclosure of classes of share capital [line items]
Ordinary shares par value \| $ / shares				$ 10
Percentage of capital reduction	15.00%	15.00%
Amount of capital reduction	$ 1,329,446	$ 43,432
Capital reduction				(128,422,000)
Ordinary shares [member]
Disclosure of classes of share capital [line items]
Maximum value of shares approved for repurchase \| $							$ 600,000	$ 600,000
Number of shares repurchased under share repurchase program					30,000,000	30,000,000
Number of shares issued				752,858,000	886,297,000	886,966,000			896,206,000
Number of shares represented by each unit of ADS			20
Number of shares outstanding				106,197,000
Capital reduction	132,945,000	132,945,000
American depositary share (each representing 20 common shares) [member]
Disclosure of classes of share capital [line items]
Number of shares issued			21,775,257
Number of shares represented by each unit of ADS			20
Number of shares outstanding				5,309,826
American depositary share before capital reduction adjustment (each representing 20 common shares) [member]
Disclosure of classes of share capital [line items]
Number of shares issued			25,620,267

Issued Capital - Movement of Ordinary Shares Issued (Detail) shares in Thousands, pure in Thousands			12 Months Ended
	Aug. 15, 2018 shares	Oct. 31, 2016 shares	Dec. 31, 2018 shares	Dec. 31, 2017 shares	Dec. 31, 2016 shares
Disclosure of classes of share capital [line items]
Cancellation of ordinary shares from capital reorganization (Note 31)		(522,080)
Capital reduction			(128,422)
Ordinary shares [member]
Disclosure of classes of share capital [line items]
Beginning balance			886,297	886,966	896,206
Restricted shares					435
Unearned restricted shares - cancelled			(502)	(669)
Share cancellation			(4,515)
Issuance of ordinary shares for capital reorganization (Note 31)		512,405			512,405
Cancellation of ordinary shares from capital reorganization (Note 31)					(522,080)
Capital reduction	132,945
Ending balance			752,858	886,297	886,966

Capital Surplus and Retained Earnings - Details of Capital Surplus (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)	Dec. 31, 2016 TWD ($)
Disclosure of reserves within equity [abstract]
Share premium	$ 5,873,743	$ 191,890	$ 5,873,743	$ 6,473,471
Restricted shares	382,506	12,496	390,401	408,051
Others	7,304	239	7,304	7,304
Capital surplus	$ 6,263,553	$ 204,625	$ 6,271,448	$ 6,888,826

Capital Surplus and Retained Earnings - Details of Retained Earnings (Detail) - TWD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of reserves within equity [abstract]
Legal reserve	$ 302,653	$ 28,680	$ 223,047
Cash dividend	$ 256,806	257,026	$ 1,792,553
Cash distribution from capital surplus		$ 599,728
Cash dividend, distribution per share	$ 0.30	$ 0.30	$ 2.09
Cash distribution from capital surplus		$ 0.70

Treasury Stock - Movement of Treasury Stock (Detail) shares in Thousands, $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018 TWD ($) shares	Dec. 31, 2018 USD ($) shares	Dec. 31, 2016 TWD ($) shares
Capital reduction	(128,422)	(128,422)
Beginning balance \| $	$ 1,007,654
Treasury stock (repurchased) \| $			$ 1,007,654
Capital reduction \| $	1,284,223
Ending balance	$ 962,503	$ 31,444
Treasury stock [member]
Treasury stock shares at beginning balance	30,085	30,085
Treasury stock shares (repurchased)			30,085
Capital reduction	(4,515)	(4,515)
Treasury stock shares at ending balance	25,570	25,570	30,085
Beginning balance	$ 1,007,654	$ 32,919
Treasury stock (repurchased) \| $			$ 1,007,654
Capital reduction	(45,151)	(1,475)
Ending balance	$ 962,503	$ 31,444	$ 1,007,654

Long-term Bank Loans - Summary of Long-term Bank Loans (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)	Dec. 31, 2018 USD ($)
Disclosure of detailed information about borrowings [Line Items]
Long-term bank loans	$ 9,789,518		$ 9,642,021	$ 319,815
Less:Fee on syndicated bank loan	(32,482)	$ (1,061)	(33,280)
Less: Current portion (fee included)	(747,422)		(2,143,168)	(24,418)
Syndicated bank loans, excluding current portion	9,042,096		7,498,853	$ 295,397
Long-term bank loans [Member]
Disclosure of detailed information about borrowings [Line Items]
Unused credit lines of long-term bank loans	$ 1,800,000		$ 2,400,000
Gross carrying amount [member]
Disclosure of detailed information about borrowings [Line Items]
Interest rate range	1.7895%		1.7895%	1.7895%
Gross carrying amount [member] \| Syndicated bank loans repayable from November 2018 to May 2023 [member]
Disclosure of detailed information about borrowings [Line Items]
Long-term bank loans	$ 9,822,000			$ 320,876
Period and payment term	Borrowing period is from May 30, 2018 to May 30, 2023; interest is repayable monthly; principal is repayable semi-annually from November 30, 2018	Borrowing period is from May 30, 2018 to May 30, 2023; interest is repayable monthly; principal is repayable semi-annually from November 30, 2018	Borrowing period is from May 30, 2018 to May 30, 2023; interest is repayable monthly; principal is repayable semi-annually from November 30, 2018
Gross carrying amount [member] \| Syndicated Bank Loans Repayable from December 2017 to June 2021 [Member]
Disclosure of detailed information about borrowings [Line Items]
Long-term bank loans			$ 9,675,301
Period and payment term	Borrowing period is from June 30, 2016 to June 30, 2021; interest is repayable monthly; principal is repayable semi-annually from December 30, 2017	Borrowing period is from June 30, 2016 to June 30, 2021; interest is repayable monthly; principal is repayable semi-annually from December 30, 2017	Borrowing period is from June 30, 2016 to June 30, 2021; interest is repayable monthly; principal is repayable semi-annually from December 30, 2017

Long-term Bank Loans - Additional Information (Detail) $ in Billions	May 15, 2018 TWD ($) Bank	May 16, 2016 TWD ($) Bank
Disclosure of detailed information about borrowings [Line Items]
Number of banks in syndicate \| Bank	11	10
Syndicated loan [member]
Disclosure of detailed information about borrowings [Line Items]
Principal amount of loan \| $	$ 12.0	$ 13.2
Maturity of loan	Five years	Five years

Long-term Bank Loans - Details of Repayment Schedule in Respect of Bank Loans (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)
Disclosure of detailed information about borrowings [Line Items]
Bank loans	$ 9,789,518	$ 319,815	$ 9,642,021
Within 1 year [member]
Disclosure of detailed information about borrowings [Line Items]
Bank loans	747,422	24,418	2,143,168
1-5 years [member]
Disclosure of detailed information about borrowings [Line Items]
Bank loans	$ 9,042,096	$ 295,397	$ 7,498,853

Retirement Benefit Plans - Additional Information (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018 TWD ($) Years Unit	Dec. 31, 2018 USD ($) Years Unit	Dec. 31, 2017 TWD ($)
Disclosure of defined benefit plans [Line Items]
Defined benefit plans expected contribution	$ 27,160	$ 887
Weighted average duration of the defined benefit obligation \| Years	13.2	13.2
Defined benefit pension plan [Member]
Disclosure of defined benefit plans [Line Items]
Number of units accrued in first tranche	2	2
Duration of first tranche	First 15 years	First 15 years
Number of units accrued in second tranche	1	1
Duration of second tranche	Thereafter 15 years	Thereafter 15 years
Maximum number of units accruable under the pension plan	45	45
Benefit measurement period	6 months	6 months
Employer contribution percentage	2.00%	2.00%
Defined contribution pension plan [member]
Disclosure of defined benefit plans [Line Items]
Employer contribution percentage	6.00%	6.00%	6.00%
Pension costs under defined contribution pension plans	$ 193,047	$ 6,307	$ 190,106

Retirement Benefit Plans - Defined Benefit Plans Amounts Recognized in Statements of Financial Position (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 TWD ($)
Surplus (deficit) in plan [abstract]
Present value of defined benefit obligations	$ (910,081)	$ (29,731)	$ (838,543)
Fair value of plan assets	389,316	12,718	360,017
Net defined benefit liability	$ (520,765)	$ (17,013)	$ (478,526)	$ (15,633)	$ (546,968)

Retirement Benefit Plans - Movements in Net Defined Benefit Liability (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)
Disclosure of net defined benefit liability (asset) [Line Items]
Beginning balance	$ (478,526)	$ (15,633)	$ (546,968)
Current service cost	(382)	(12)	(386)
Interest (expense) income	(8,138)	(266)	(8,010)
Total	(487,046)	(15,911)	(555,364)
Return of plan assets (excluding the amount included in interest income or expense)	8,145	266	(1,842)
Financial assumption movement effect	(56,934)	(1,860)	28,506
Experience adjustments	(11,172)	(365)	24,174
Gain (loss) on remeasurement, net defined benefit liability (asset)	(59,961)	(1,959)	50,838
Pension fund contribution	26,242	857	26,000
Ending balance	(520,765)	$ (17,013)	(478,526)
Present Value of Defined Benefit Obligation [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Beginning balance	(838,543)		(894,163)
Current service cost	(382)		(386)
Interest (expense) income	(14,429)		(13,236)
Total	(853,354)		(907,785)
Financial assumption movement effect	(56,934)		28,506
Experience adjustments	(11,172)		24,174
Gain (loss) on remeasurement, net defined benefit liability (asset)	(68,106)		52,680
Paid pension	11,379		16,562
Ending balance	(910,081)		(838,543)
Fair Value of Plan Assets [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Beginning balance	360,017		347,195
Interest (expense) income	6,291		5,226
Total	366,308		352,421
Return of plan assets (excluding the amount included in interest income or expense)	8,145		(1,842)
Gain (loss) on remeasurement, net defined benefit liability (asset)	8,145		(1,842)
Pension fund contribution	26,242		26,000
Paid pension	(11,379)		(16,562)
Ending balance	$ 389,316		$ 360,017

Retirement Benefit Plans - Principal Actuarial Assumptions Used and Sensitivity Analysis of Present Value of Defined Benefit Obligation Effected by Changes of Principal Actuarial Assumptions (Detail)	Dec. 31, 2018	Dec. 31, 2017
Disclosure of sensitivity analysis for actuarial assumptions [abstract]
Discount rate	1.25%	1.75%
Future salary increases	3.50%	3.50%

Retirement Benefit Plans - Sensitivity Analysis of Present Value of Defined Benefit Obligations Effected by Changes of Significant Actuarial Assumptions (Detail) - TWD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Actuarial assumption of discount rates [member]
Disclosure of sensitivity analysis for actuarial assumptions [Line Items]
Percentage increase in assumption	0.25%	0.25%
Effect on present value of defined benefit obligations due to increase in assumption	$ (29,052)	$ (27,192)
Percentage decrease in assumption	0.25%	0.25%
Effect on present value of defined benefit obligations due to decrease in assumption	$ 30,430	$ 28,506
Actuarial assumption of expected rates of salary increases [member]
Disclosure of sensitivity analysis for actuarial assumptions [Line Items]
Percentage increase in assumption	0.25%	0.25%
Effect on present value of defined benefit obligations due to increase in assumption	$ 29,692	$ 27,955
Percentage decrease in assumption	0.25%	0.25%
Effect on present value of defined benefit obligations due to decrease in assumption	$ (28,513)	$ (26,816)

Retirement Benefit Plans - Analysis of Timing of the Future Pension Payment (Detail) - Dec. 31, 2018 $ in Thousands, $ in Thousands	TWD ($)	USD ($)
Disclosure of net defined benefit liability (asset) [Line Items]
Defined benefit plan expected future pension payments	$ 363,804	$ 11,885
Within 1 year [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Defined benefit plan expected future pension payments	32,904	1,075
1-2 years [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Defined benefit plan expected future pension payments	35,835	1,170
2-5 years [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Defined benefit plan expected future pension payments	105,665	3,452
5-10 years [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Defined benefit plan expected future pension payments	$ 189,400	$ 6,188

Other Payables - Summary of Other Payables (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)
Trade and other current payables [abstract]
Salaries and bonus payable	$ 595,575	$ 19,457	$ 601,239
Interest payable	963	31	2,854
Pension payable	32,038	1,047	32,402
Employees' compensation payable	212,391	6,939	371,912
Directors' remuneration payable	9,951	325	18,596
Other expense payable	827,564	27,036	953,179
Other payables	$ 1,678,482	$ 54,835	$ 1,980,182

Current Provisions - Movements in Provisions (Detail) - 12 months ended Dec. 31, 2018 $ in Thousands, $ in Thousands	TWD ($)	USD ($)
Disclosure of other provisions [Line Items]
Beginning balance	$ 127,311
Ending balance	29,352	$ 959
Provisions for deficiency compensation [member]
Disclosure of other provisions [Line Items]
Beginning balance	57,155	1,867
Provision	14,211	465
Reversal	(24,451)	(799)
Payment	(17,563)	(574)
Ending balance	$ 29,352	$ 959

Current Refund Liabilities - Summary of Movements in Refund Liabilities (Detail) - 12 months ended Dec. 31, 2018 $ in Thousands, $ in Thousands	TWD ($)	USD ($)
Disclosure of refund liability [abstract]
Beginning balance	$ 70,156	$ 2,292
Provision	44,950	1,468
Reversal	(7,413)	(242)
Payment	(75,066)	(2,452)
Ending balance	$ 32,627	$ 1,066

Short-term Bank Loans - Summary of Short-term Bank Loans (Detail) $ in Thousands	Dec. 31, 2017 TWD ($)
Disclosure of detailed information about borrowings [Line Items]
Unsecured bank loans	$ 969,353
Bottom of range [member]
Disclosure of detailed information about borrowings [Line Items]
Interest rate range	0.55%
Top of range [member]
Disclosure of detailed information about borrowings [Line Items]
Interest rate range	1.71%

Significant Commitments and Contingencies - Future Minimum Lease Obligation Payable under Operating Lease Contracts (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)
Disclosure of finance lease and operating lease by lessee [Line Items]
Minimum finance lease payments payable	$ 320,214	$ 10,461	$ 309,423
Within 1 year [member]
Disclosure of finance lease and operating lease by lessee [Line Items]
Minimum finance lease payments payable	68,631	2,242	39,342
1-5 years [member]
Disclosure of finance lease and operating lease by lessee [Line Items]
Minimum finance lease payments payable	140,137	4,578	130,182
Over 5 years [member]
Disclosure of finance lease and operating lease by lessee [Line Items]
Minimum finance lease payments payable	$ 111,446	$ 3,641	$ 139,899

Capital Reorganization - Additional Information (Detail) $ / shares in Units, $ in Thousands, $ in Thousands		12 Months Ended
	Oct. 31, 2016 TWD ($) $ / shares shares	Dec. 31, 2016 TWD ($) shares	Dec. 31, 2018 shares	Dec. 31, 2017 shares	Oct. 31, 2016 USD ($) shares	Oct. 30, 2016 TWD ($)	Dec. 31, 2015 shares
Disclosure of capital reorganization [Line Items]
Cash per share the former parent is entitles to receive under the Merger Agreement \| $ / shares	$ 3.71
Total consideration paid	$ 3,208,310	$ 3,208,310			$ 101,657
Directly attributable transaction cost \| $	133,311	133,311
Cash for capital reorganization \| $	$ 3,341,621	3,341,621
Number of shares cancelled	522,080,000
Reduction of unappropriated retained earnings through capital transfer \| $	$ (5,052,343)	$ (5,052,343)
Decrease in number of shares	(9,675,000)
Equity attributable to predecessors' interests \| $						$ 1,692,918
American depositary share (each representing 20 common shares) [member]
Disclosure of capital reorganization [Line Items]
Number of units of ADS the former parent is entitled to receive under the Merger Agreement \| $ / shares	$ 0.9355
Number of shares represented by each unit of ADS	20
Number of shares issued	21,775,257				21,775,257
Ordinary shares [member]
Disclosure of capital reorganization [Line Items]
Number of shares represented by each unit of ADS	20
Number of shares issued		886,966,000	752,858,000	886,297,000			896,206,000
Issuance of ordinary shares for capital reorganization	512,405,000	512,405,000
Number of shares cancelled		522,080,000
American depositary share before capital reduction adjustment (each representing 20 common shares) [member]
Disclosure of capital reorganization [Line Items]
Number of shares issued	25,620,267				25,620,267

Supplementary Cash Flow Information - Partial Cash Paid for Investing and Financing Activities (Detail) $ in Thousands, $ in Thousands		12 Months Ended
	Oct. 31, 2016 TWD ($)	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)	Dec. 31, 2016 TWD ($)	Oct. 31, 2016 USD ($)
Statement of cash flows [abstract]
Purchase in property, plant and equipment		$ 4,945,570	$ 161,567	$ 4,849,331	$ 4,690,995
Add: Beginning balance of payable to contractors and equipment suppliers		713,313	23,303	839,983	523,962
Add: Beginning balance of lease payable		29,842	975	94,952
Less: Ending balance of payable to contractors and equipment suppliers		(1,516,735)	(49,550)	(878,065)	(647,486)
Less: Ending balance of lease payable		(17,792)	(581)	(84,192)	(96,006)
Less: Transfer from prepaid equipment (shown as "Other non-current assets")				(139,304)
Cash paid for acquisition of property, plant and equipment		$ 4,154,198	$ 135,714	4,682,705	4,471,465
Net assets acquired from ChipMOS Bermuda					12,987,736
Less: Issuance of shares					(9,779,426)
Cash consideration	$ 3,208,310				3,208,310	$ 101,657
Directly attributable transaction cost	133,311				133,311
Cash paid for capital reorganization	$ 3,341,621				$ 3,341,621
Disposal of a subsidiary				2,166,151
Add: Ending balance of other payables				64,393
Less: Cash and cash equivalents of discontinued operations				(449,331)
Cash received from disposal of a subsidiary				$ 1,781,213

Supplementary Cash Flow Information - Reconciliation of Liabilities Arising from Financing Activities (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning balance	$ 10,612,745		$ 10,751,409
Cash flow	(859,382)		(155,379)
Non-Cash flow, Amortization of loans fee	37,247		16,715
Ending balance	9,790,610	$ 319,850	10,612,745
Long-term bank loans (include the current portion) [member]
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning balance	9,642,021		10,750,005
Cash flow	110,250		(1,124,699)
Non-Cash flow, Amortization of loans fee	37,247		16,715
Ending balance	9,789,518	319,815	9,642,021
Short-term bank loans [member]
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning balance	969,353
Cash flow	(969,353)		969,353
Ending balance			969,353
Guarantee deposits [member]
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning balance	1,371		1,404
Cash flow	(279)		(33)
Ending balance	$ 1,092	$ 35	$ 1,371

Related Party Transactions - Summary of Purchases of Materials (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)
Disclosure of transactions between related parties [Line Items]
Purchases of materials	$ 136,269	$ 4,452	$ 1,036
Unimos Shanghai [member]
Disclosure of transactions between related parties [Line Items]
Purchases of materials	3,775	123	906
JMC ELECTRONICS CO., LTD. [member]
Disclosure of transactions between related parties [Line Items]
Purchases of materials	$ 132,494	$ 4,329	$ 130

Related Party Transactions - Additional Information (Detail) ¥ in Thousands, $ in Thousands, $ in Thousands	1 Months Ended						12 Months Ended
	Jan. 31, 2018 TWD ($)	Jan. 31, 2018 USD ($)	Jun. 30, 2017 TWD ($)	Jan. 31, 2017 USD ($)	May 31, 2016 USD ($)	Oct. 31, 2011 CNY (¥) Installments	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)	Dec. 31, 2016 TWD ($)	Dec. 31, 2018 USD ($)
Disclosure of transactions between related parties [Line Items]
Payment terms of the purchases from associates							30 to 90 days	30 to 90 days
Acquisition of investment in associate							$ 794,694	$ 25,962	$ 1,373,486
Long-term deferred revenue									24,898
Royalty income							43,224	1,412	11,998
ChipMOS Bermuda and Unimos Shanghai [member]
Disclosure of transactions between related parties [Line Items]
Licensing fee \| ¥						¥ 27,400
License agreement term						10 years
Receipts in advance							1,013		1,039		$ 33
Royalty income							12,506	409	9,170
Number of quarterly installments \| Installments						40
Quarterly installment amount \| ¥						¥ 685
ChipMOS BVI and Unimos Shanghai [member]
Disclosure of transactions between related parties [Line Items]
Acquisition of investment in associate	$ 794,694	$ 25,962	$ 1,373,486						$ 0	$ 0
Unimos Shanghai, Patent Licensing Agreement [member]
Disclosure of transactions between related parties [Line Items]
Licensing fee				$ 1,000	$ 2,500
License agreement term									10 years
Percentage of licensed products revenue									0.50%
Receipts in advance							0		$ 3,018
Long-term deferred revenue							0		24,898
Royalty income							$ 30,683	$ 1,002	$ 2,828

Related Party Transactions - Summary of Disposal of Property, Plant and Equipment (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)	Dec. 31, 2016 TWD ($)
Disclosure of transactions between related parties [Line Items]
Selling price	$ 18,160	$ 593	$ 306,634	$ 59,134
Gain on disposal	$ 14,274	$ 466	132,777	$ 2,575
Unimos Shanghai [member]
Disclosure of transactions between related parties [Line Items]
Selling price			21,982
Gain on disposal			$ 20,240

Related Party Transactions - Key Management Personnel Compensation (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)	Dec. 31, 2016 TWD ($)
Disclosure of transactions between related parties [abstract]
Salaries and short-term employee benefits	$ 151,095	$ 4,936	$ 188,105	$ 152,319
Post-employment compensation	2,067	68	5,622	3,335
Share-based payments	6,763	221	18,736	109,255
Total key management personnel compensation	$ 159,925	$ 5,225	$ 212,463	$ 264,909

Pledged or Mortgaged Assets - Certain Assets Provided as Collateral Mainly for Long-term Bank Loans and Leases (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)
Disclosure assets pledged as collateral [abstract]
Non-current financial assets at amortized cost	$ 68,388	$ 2,234
Property, plant and equipment, net	9,672,238	315,983	$ 7,164,089
Other non-current financial assets			70,241
Assets pledged as collateral for liabilities	$ 9,740,626	$ 318,217	$ 7,234,330

Financial Risk Management and Fair Values of Financial Instruments - Summary of Financial Instruments by Category (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)
Financial assets at fair value through profit or loss
Financial assets mandatorily measured at fair value through profit or loss	$ 11,471	$ 375
Financial assets at fair value through other comprehensive income
Designation of equity instruments	174,357	5,696
Available-for-sale financial assets	0	0	$ 0
Non-current financial assets carried at cost			20,890
Financial assets at amortized cost/loans and receivables
Cash and cash equivalents	4,642,522	151,667	8,035,714
Financial assets at amortized cost	268,271	8,763
Accounts and notes receivable	4,747,288	155,090	4,015,734
Accounts receivable - related parties	140	5	11
Other receivables	63,037	2,059	56,716
Other receivables - related parties	3,131	102	4,534
Refundable deposits	22,006	719	21,342
Other financial assets			70,241
Financial assets	9,932,223	324,476	12,225,182
Financial liabilities at amortized cost
Short-term bank loans			969,353
Accounts payable	637,271	20,819	687,960
Accounts payable - related parties	347	11	226
Payables to contractors and equipment suppliers	1,516,735	49,550	713,313
Other payables	1,678,482	54,835	1,980,182
Other payables - related parties	218	7	36
Long-term bank loans (including current portion)	9,789,518	319,815	9,642,021
Guarantee deposits	1,092	35	1,371
Financial liabilities	$ 13,623,663	$ 445,072	$ 13,994,462

Financial Risk Management and Fair Values of Financial Instruments - Information on Assets and Liabilities Denominated in Foreign Currencies whose Values would be Materially Affected by Exchange Rate Fluctuations (Detail) ¥ in Thousands, ¥ in Thousands, $ in Thousands, $ in Thousands	Dec. 31, 2018 TWD ($) $ / CNY $ / JPY $ / $	Dec. 31, 2018 USD ($) $ / CNY $ / JPY $ / $	Dec. 31, 2018 CNY (¥) $ / CNY $ / JPY $ / $	Dec. 31, 2018 JPY (¥) $ / CNY $ / JPY $ / $	Dec. 31, 2017 TWD ($) $ / CNY $ / JPY $ / $	Dec. 31, 2017 USD ($) $ / CNY $ / JPY $ / $	Dec. 31, 2017 CNY (¥) $ / CNY $ / JPY $ / $	Dec. 31, 2017 JPY (¥) $ / CNY $ / JPY $ / $
Disclosure of detailed information about financial instruments [Line Items]
Assets denominated in foreign currencies	$ 9,932,223	$ 324,476			$ 12,225,182
Exchange rate	30.61	30.61	30.61	30.61
Currency Risk [member] \| US$ [member]
Disclosure of detailed information about financial instruments [Line Items]
Assets denominated in foreign currencies	$ 5,229,843	$ 170,270			6,192,044	$ 208,066
Liabilities denominated in foreign currencies	$ 559,934	$ 18,230			$ 477,231	$ 16,036
Currency Risk [member] \| US$ [member] \| Financial Liability [member]
Disclosure of detailed information about financial instruments [Line Items]
Exchange rate	30.7150	30.7150	30.7150	30.7150	29.7600	29.7600	29.7600	29.7600
Currency Risk [member] \| US$ [member] \| Financial Asset [member]
Disclosure of detailed information about financial instruments [Line Items]
Exchange rate	30.7150	30.7150	30.7150	30.7150	29.7600	29.7600	29.7600	29.7600
Currency Risk [member] \| JPY [member]
Disclosure of detailed information about financial instruments [Line Items]
Assets denominated in foreign currencies	$ 49,396			¥ 177,557	$ 210,899			¥ 798,254
Liabilities denominated in foreign currencies	$ 677,734			¥ 2,436,140	$ 283,072			¥ 1,071,432
Currency Risk [member] \| JPY [member] \| Financial Liability [member]
Disclosure of detailed information about financial instruments [Line Items]
Exchange rate \| $ / JPY	0.2782	0.2782	0.2782	0.2782	0.2642	0.2642	0.2642	0.2642
Currency Risk [member] \| JPY [member] \| Financial Asset [member]
Disclosure of detailed information about financial instruments [Line Items]
Exchange rate \| $ / JPY	0.2782	0.2782	0.2782	0.2782	0.2642	0.2642	0.2642	0.2642
Currency Risk [member] \| RMB [member]
Disclosure of detailed information about financial instruments [Line Items]
Assets denominated in foreign currencies	$ 39,577		¥ 8,850		$ 764,564		¥ 167,484
Currency Risk [member] \| RMB [member] \| Financial Asset [member]
Disclosure of detailed information about financial instruments [Line Items]
Exchange rate \| $ / CNY	4.4720	4.4720	4.4720	4.4720	4.5650	4.5650	4.5650	4.5650

Financial Risk Management and Fair Values of Financial Instruments - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)	Dec. 31, 2016 TWD ($)	Dec. 31, 2018 USD ($)
Disclosure of detailed information about financial instruments [Line Items]
Realized and unrealized gain and loss arising from significant foreign exchange variation	$ 93,104,000	$ 3,041	$ (418,970,000)	$ (195,326,000)
Financial instruments measured at fair value			0
Non financial instruments measured at fair value			0
Movement of financial instruments			0
General increase or decrease of 100 basis points (1%) in interest rates [member]
Disclosure of detailed information about financial instruments [Line Items]
Estimated decrease or increase in the Group's profit and equity based on an increase or decrease in the interest rates	$ 98,220,000		$ 106,447,000		$ 3,209

Financial Risk Management and Fair Values of Financial Instruments - Details of Exposure to Currency Risk Arising from Recognized Monetary Assets or Liabilities Denominated in a Currency Other Than Functional Currency (Detail) - Currency Risk [member] - TWD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Financial assets, class [member] \| US$ [member]
Disclosure of nature and extent of risks arising from financial instruments [Line Items]
Change in exchange rate	5.00%	5.00%
Financial assets, class [member] \| JPY [member]
Disclosure of nature and extent of risks arising from financial instruments [Line Items]
Change in exchange rate	5.00%	5.00%
Financial assets, class [member] \| RMB [member]
Disclosure of nature and extent of risks arising from financial instruments [Line Items]
Change in exchange rate	5.00%	5.00%
Financial liabilities, class [member] \| US$ [member]
Disclosure of nature and extent of risks arising from financial instruments [Line Items]
Change in exchange rate	5.00%	5.00%
Financial liabilities, class [member] \| JPY [member]
Disclosure of nature and extent of risks arising from financial instruments [Line Items]
Change in exchange rate	5.00%	5.00%
Profit and Loss [member] \| Financial assets, class [member] \| US$ [member]
Disclosure of nature and extent of risks arising from financial instruments [Line Items]
Effect of change in exchange rate	$ 261,492	$ 309,602
Profit and Loss [member] \| Financial assets, class [member] \| JPY [member]
Disclosure of nature and extent of risks arising from financial instruments [Line Items]
Effect of change in exchange rate	2,470	10,545
Profit and Loss [member] \| Financial assets, class [member] \| RMB [member]
Disclosure of nature and extent of risks arising from financial instruments [Line Items]
Effect of change in exchange rate	1,979	38,228
Profit and Loss [member] \| Financial liabilities, class [member] \| US$ [member]
Disclosure of nature and extent of risks arising from financial instruments [Line Items]
Effect of change in exchange rate	27,997	23,862
Profit and Loss [member] \| Financial liabilities, class [member] \| JPY [member]
Disclosure of nature and extent of risks arising from financial instruments [Line Items]
Effect of change in exchange rate	$ 33,887	$ 14,154

Financial Risk Management and Fair Values of Financial Instruments - Summary of Loss Rate Methodology (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2018 TWD ($)
Contract assets [member]
Disclosure of detailed information about financial instruments [Line Items]
Expected loss rate	0.045%
Total carrying amount	$ 299,970
Loss allowance	$ (135)
Accounts receivable including related parties [member]
Disclosure of detailed information about financial instruments [Line Items]
Expected loss rate	0.045%
Total carrying amount	$ 4,747,974
Loss allowance	$ (2,141)
Other receivable including related parties [member]
Disclosure of detailed information about financial instruments [Line Items]
Expected loss rate	0.045%
Total carrying amount	$ 66,181
Loss allowance	$ (13)

Financial Risk Management and Fair Values of Financial Instruments - Summary of Movements in Relation to Loss Allowance for Contract Assets, Accounts Receivable and Other Receivables (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Jan. 01, 2018 TWD ($)
Disclosure of detailed information about financial instruments [Line Items]
Financial assets	$ 12,225,182	$ 324,476
Financial assets beginning balance	12,225,182
Financial assets ending balance	9,932,223	$ 324,476
IFRS 9 [member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets			$ 171,009
Contract assets [member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets	(135)
Adjustments for applying new standards	(115)
Provision for impairment loss	(20)
Financial assets ending balance	(135)
Contract assets [member] \| IFRS 9 [member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets	(115)
Financial assets beginning balance	(115)
Accounts receivable including related parties [member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets	(2,141)
Adjustments for applying new standards	(1,819)
Provision for impairment loss	(322)
Financial assets ending balance	(2,141)
Accounts receivable including related parties [member] \| IFRS 9 [member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets	(1,819)
Financial assets beginning balance	(1,819)
Other receivable including related parties [member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets	(13)
Adjustments for applying new standards	(7)
Provision for impairment loss	(7)
Reversal of impairment loss	1
Financial assets ending balance	(13)
Other receivable including related parties [member] \| IFRS 9 [member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets	(7)
Financial assets beginning balance	$ (7)

- Definition

The amount of assets that are: (a) cash; (b) an equity instrument of another entity; (c) a contractual right: (i) to receive cash or another financial asset from another entity; or (ii) to exchange financial assets or financial liabilities with another entity under conditions that are potentially favourable to the entity; or (d) a contract that will, or may be, settled in the entity’s own equity instruments and is: (i) a non-derivative for which the entity is, or may be, obliged to receive a variable number of the entity’s own equity instruments; or (ii) a derivative that will, or may be, settled other than by the exchange of a fixed amount of cash or another financial asset for a fixed number of the entity’s own equity instruments. For this purpose the entity’s own equity instruments do not include puttable financial instruments classified as equity instruments in accordance with paragraphs 16A-16B of IAS 32, instruments that impose on the entity an obligation to deliver to another party a pro rata share of the net assets of the entity only on liquidation and are classified as equity instruments in accordance with paragraphs 16C-16D of IAS 32, or instruments that are contracts for the future receipt or delivery of the entity’s own equity instruments. [Refer: Financial instruments, class [member]; Financial liabilities]

+ References + Details

Financial Risk Management and Fair Values of Financial Instruments - Maturity Profile of Non-derivative Financial Liabilities Based on Contracted Undiscounted Payments (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Short-term bank loans			$ 971,813
Long-term bank loans (including current portion)	$ 10,476,570	$ 342,260	10,061,726
Accounts payable and payables to contractors and equipment suppliers (including related parties)	2,154,353	70,380	1,401,499
Other payables (including related parties)	1,678,700	54,842	1,980,218
Lease obligations payable	18,000	588	30,532
Guarantee deposits	1,092	35	1,371
Total	14,328,715	$ 468,105	14,447,159
Within 1 year [member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Short-term bank loans			971,813
Long-term bank loans (including current portion)	927,243		2,321,459
Accounts payable and payables to contractors and equipment suppliers (including related parties)	2,154,353		1,401,499
Other payables (including related parties)	1,678,700		1,980,218
Lease obligations payable	18,000		12,266
Total	4,778,296		6,687,255
1-5 years [member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Long-term bank loans (including current portion)	9,549,327		7,740,267
Lease obligations payable			18,266
Total	9,549,327		7,758,533
Over 5 years [member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Guarantee deposits	1,092		1,371
Total	$ 1,092		$ 1,371

Financial Risk Management and Fair Values of Financial Instruments - Summary of Natures of Assets and Liabilities (Detail) - 12 months ended Dec. 31, 2018 $ in Thousands, $ in Thousands	TWD ($)	USD ($)	USD ($)
Disclosure of detailed information about financial instruments [Line Items]
Financial assets at fair value	$ 185,828	$ 6,071
Foreign partnership interest [member] \| Recurring fair value measurement [member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets at fair value through profit or loss	11,471		$ 375
Foreign unlisted stocks [member] \| Recurring fair value measurement [member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets at fair value through other comprehensive income	174,357		$ 5,696
Level 3 [member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets at fair value	185,828
Level 3 [member] \| Foreign partnership interest [member] \| Recurring fair value measurement [member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets at fair value through profit or loss	11,471
Level 3 [member] \| Foreign unlisted stocks [member] \| Recurring fair value measurement [member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets at fair value through other comprehensive income	$ 174,357

Financial Risk Management and Fair Values of Financial Instruments - Summary of Movements of Level 3 (Detail) - 12 months ended Dec. 31, 2018 $ in Thousands, $ in Thousands	TWD ($)	USD ($)
Disclosure of detailed information about financial instruments [Line Items]
Movement of financial instruments beginning balance	$ 0
Debt instruments [member]
Disclosure of detailed information about financial instruments [Line Items]
Effects on initial application of IFRS 9	11,433	$ 374
Gains or losses recognized in profit or loss Recorded as non-operating income (expenses)	38	1
Gains or losses recognized in other comprehensive income	0	0
Movement of financial instruments ending balance	11,471	375
Equity instruments [member]
Disclosure of detailed information about financial instruments [Line Items]
Effects on initial application of IFRS 9	89,335	2,918
Gains or losses recognized in other comprehensive income	0	0
Recorded as unrealized gains on valuation of financial assets at fair value through other comprehensive income	85,022	2,778
Movement of financial instruments ending balance	$ 174,357	$ 5,696

Financial Risk Management and Fair Values of Financial Instruments - Summary of Qualitative Information and Sensitivity Analysis of Changes in Significant Unobservable Inputs Under Valuation Model Used in Level Fair Value Measurement (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2018 TWD ($)
Non derivative equity instruments [member] \| Foreign unlisted stocks [member]
Disclosure of significant unobservable inputs used in fair value measurement of equity [line items]
Fair value	$ 174,357
Valuation technique	Comparable companies
Non derivative equity instruments [member] \| Foreign unlisted stocks [member] \| Price book value multiple [member]
Disclosure of significant unobservable inputs used in fair value measurement of equity [line items]
Range (weighted average method)	1.19%
Relationship of inputs to fair value	The higher the multiple, the higher the fair value
Non derivative equity instruments [member] \| Foreign unlisted stocks [member] \| Enter prise value EBITDA multiple [member]
Disclosure of significant unobservable inputs used in fair value measurement of equity [line items]
Range (weighted average method)	7.69%
Relationship of inputs to fair value	The higher the multiple, the higher the fair value
Non derivative equity instruments [member] \| Foreign unlisted stocks [member] \| Discount for lack of marketability [member]
Disclosure of significant unobservable inputs used in fair value measurement of equity [line items]
Range (weighted average method)	15.80%
Relationship of inputs to fair value	The higher the discount for lack of marketability, the lower the fair value
Non derivative debt instruments [member] \| Foreign partnership interest [member]
Disclosure of significant unobservable inputs used in fair value measurement of equity [line items]
Fair value	$ 11,471
Valuation technique	Discounted cash flow
Non derivative debt instruments [member] \| Foreign partnership interest [member] \| Discount rate [member]
Disclosure of significant unobservable inputs used in fair value measurement of equity [line items]
Range (weighted average method)	0.35%
Relationship of inputs to fair value	The lower the discount rate, the higher the fair value

Financial Risk Management And Fair Values Of Financial Instruments - Summary of Effect of Profit or Loss or of Other Comprehensive Income from Financial Assets Categorized (Detail) - Financial instruments at fair value through other comprehensive income [member] $ in Thousands	12 Months Ended
	Dec. 31, 2018 TWD ($)
Disclosure of significant unobservable inputs used in fair value measurement of equity [line items]
Favorable Changes	$ 3,725
Unfavorable Changes In Fair Value	3,630
Enter prise value EBITDA multiple [member]
Disclosure of significant unobservable inputs used in fair value measurement of equity [line items]
Favorable Changes	1,563
Unfavorable Changes In Fair Value	1,512
Discount for lack of marketability [member]
Disclosure of significant unobservable inputs used in fair value measurement of equity [line items]
Favorable Changes	2,093
Unfavorable Changes In Fair Value	2,050
Foreign unlisted stocks [member] \| Price book value multiple [member]
Disclosure of significant unobservable inputs used in fair value measurement of equity [line items]
Favorable Changes	69
Unfavorable Changes In Fair Value	$ 68

Share-based Payments - Additional Information (Detail) $ / shares in Units, pure in Thousands, $ in Thousands, $ in Thousands				12 Months Ended
	May 10, 2016	Jul. 21, 2015	Nov. 12, 2014 $ / shares shares	Dec. 31, 2018 TWD ($) $ / shares	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)	Dec. 31, 2016 TWD ($)
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Par value				$ 10
Compensation expenses				$ 41,043	$ 1,341	$ 123,021	$ 356,463
Restricted Shares [member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Shares available for issuance \| shares			17,300,000
Par value			$ 10
Granting price			$ 0
Number of shares issued	1,548	15,752

Share-based Payments - Years of Service and Performance Conditions of Restricted Shares (Detail)	12 Months Ended
	Dec. 31, 2017
Within 1 year [member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Years of service following the receipt of restricted shares	Continuous service for one year
Grade of performance appraisal	>=B+
Compliance of terms agreed by the staff and the Company	No violation
Vesting ratio of numbers of restricted shares received	30.00%
1-2 years [member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Years of service following the receipt of restricted shares	Continuous service for two years
Grade of performance appraisal	>=B+
Compliance of terms agreed by the staff and the Company	No violation
Vesting ratio of numbers of restricted shares received	30.00%
2-3 years [member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Years of service following the receipt of restricted shares	Continuous service for three years
Grade of performance appraisal	>=B+
Compliance of terms agreed by the staff and the Company	No violation
Vesting ratio of numbers of restricted shares received	40.00%

Capital Management - Percentages of Liabilities to Assets Ratio Used for Monitoring Capital (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)
Disclosure of objectives, policies and processes for managing capital [abstract]
Total liabilities	$ 15,112,545	$ 493,713	$ 15,138,993
Total assets	$ 33,133,718	$ 1,082,448	$ 33,259,942
Liabilities to assets ratio	45.61%	45.61%	45.52%

Significant Events After the Reporting Periods - Additional Information (Detail) - Apr. 08, 2019 - Disposal of major subsidiary [member] - JMC ELECTRONICS CO., LTD. [member] $ in Thousands, $ in Thousands	TWD ($) shares	USD ($) shares
Disclosure of events after reporting period [Line Items]
Number of common shares disposed	9,100,000	9,100,000
Percentage of disposal of equity investment in associate	9.10%	9.10%
Gain on disposal of investment in associates	$ 973,609	$ 31,807

Financial Statements Schedule: Valuation and Qualifying Accounts (Detail) - TWD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Allowance for Impairment of property, plant and equipment [member]
Disclosure of details of valuation and qualifying accounts [Line Items]
January 1	$ 320,455	$ 359,270	$ 1,994,715
Additions charged to expense		956	8,198
Deduction/Write-offs	(2,862)	(39,771)	(45,319)
Exchange difference on translations of foreign financial statement			(118,046)
Non-current assets held for sale			(1,480,278)
December 31	317,593	320,455	359,270
Allowance for Impairment of Obsolescence and Decline in Market Value of Inventories [Member]
Disclosure of details of valuation and qualifying accounts [Line Items]
January 1	53,714	154,841	95,036
Additions charged to expense			66,894
Deduction/Write-offs	(17,557)	(101,127)
Exchange difference on translations of foreign financial statement			(557)
Non-current assets held for sale			(6,532)
December 31	36,157	53,714	154,841
Allowance for impairment of accounts receivable [member]
Disclosure of details of valuation and qualifying accounts [Line Items]
January 1		87
Additions charged to expense			87
Deduction/Write-offs		(87)
December 31			$ 87
Loss allowance for accounts receivable [member]
Disclosure of details of valuation and qualifying accounts [Line Items]
January 1	1,819
Additions charged to expense	322
December 31	$ 2,141	$ 1,819

Effects on Initial Application of IFRS 9 and Information for the Years Ended December 31, 2016 and 2017 in Conformity With IAS 39 - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017 TWD ($)	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Jan. 01, 2018 TWD ($)	Jan. 01, 2018 USD ($)
Disclosure of initial application of standards or interpretations [line items]
Contract assets		$ 299,835	$ 9,795,000
Retained earnings	$ 2,815,966	3,602,663	117,696,000
Deferred tax assets	212,372	$ 226,716	$ 7,407,000
VIGOUR TECHNOLOGY Corporation [member]
Disclosure of initial application of standards or interpretations [line items]
Impairment loss of investments	$ 41,336
Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of initial application of standards or interpretations [line items]
Contract assets				$ (115)	$ (4,000)
Accounts receivable				(1,819)	(59,000)
Other receivables				(5)	(163)
Other receivables-related parties				(2)	(65)
Retained earnings				(1,940)	(63,000)
Deferred tax assets				$ 1	$ 33

Effects on Initial Application of IFRS 9 and Information for the Years Ended December 31, 2016 and 2017 in Conformity With IAS 39 - Summary of Carrying Amount of Financial Assets Transferred (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Jan. 01, 2018 TWD ($)	Jan. 01, 2018 USD ($)	Dec. 31, 2017 TWD ($)
Disclosure of financial assets [Line Items]
Measured at fair value through other comprehensive income	$ 174,357	$ 5,696
Measured at amortized cost	268,271	8,763
Financial assets	9,932,223	324,476			$ 12,225,182
Retained earnings	$ 3,602,663	$ 117,696			$ 2,815,966
Financial assets at fair value, class [member]
Disclosure of financial assets [Line Items]
Measured at fair value through profit or loss			$ 493
Measured at fair value through other comprehensive income			50,801
Financial assets			51,294
Impairment loss adjustment [member]
Disclosure of financial assets [Line Items]
Measured at fair value through other comprehensive income			28,584
Financial assets			28,584
IAS 39 [member]
Disclosure of financial assets [Line Items]
Measured at cost			20,890
Other financial assets			70,241	$ 2,295
Financial assets			91,131
IFRS 9 [member]
Disclosure of financial assets [Line Items]
Measured at fair value through profit or loss			11,433
Measured at fair value through other comprehensive income			89,335
Measured at amortized cost			70,241	2,295
Financial assets			171,009
Transferred into and measured at fair value through profit or loss [member]
Disclosure of financial assets [Line Items]
Measured at cost			(10,940)
Measured at fair value through profit or loss			10,940
Transferred into and measured at fair value through other comprehensive income [member]
Disclosure of financial assets [Line Items]
Measured at cost			(9,950)
Measured at fair value through other comprehensive income			9,950
Transfer into and measured at amortized cost [member]
Disclosure of financial assets [Line Items]
Other financial assets			(70,241)
Measured at amortized cost			70,241
Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of financial assets [Line Items]
Retained earnings			(1,940)	$ (63)
Increase (decrease) due to changes in accounting policy required by IFRSs [member] \| Financial assets at fair value, class [member]
Disclosure of financial assets [Line Items]
Retained earnings			493
Other equity interest			79,385
Increase (decrease) due to changes in accounting policy required by IFRSs [member] \| Impairment loss adjustment [member]
Disclosure of financial assets [Line Items]
Retained earnings			28,584
Other equity interest			(28,584)
Increase (decrease) due to changes in accounting policy required by IFRSs [member] \| Income tax adjustment [member]
Disclosure of financial assets [Line Items]
Other equity interest			(8,636)
Increase (decrease) due to changes in accounting policy required by IFRSs [member] \| IFRS 9 [member]
Disclosure of financial assets [Line Items]
Retained earnings			29,077
Other equity interest			$ 42,165

Effects on Initial Application of IFRS 9 and Information for the Years Ended December 31, 2016 and 2017 in Conformity With IAS 39 - Summary of Carrying Amount of Financial Assets Transferred (Parenthetical) (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Jan. 01, 2018 TWD ($)	Jan. 01, 2018 USD ($)	Dec. 31, 2017 TWD ($)
Disclosure of financial assets [Line Items]
Financial assets at amortized cost	$ 268,271	$ 8,763
Retained earnings	3,602,663	117,696			$ 2,815,966
Deferred tax liabilities	$ 308,759	$ 10,087			$ 174,293
Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of financial assets [Line Items]
Retained earnings			$ (1,940)	$ (63)
IAS 39 [member]
Disclosure of financial assets [Line Items]
Other financial assets			70,241	2,295
IFRS 9 [member]
Disclosure of financial assets [Line Items]
Financial assets at amortized cost			70,241	2,295
IFRS 9 [member] \| Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of financial assets [Line Items]
Retained earnings			29,077
Other equity interest			42,165
Financial assets at fair value through other comprehensive income, category [member] \| Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of financial assets [Line Items]
Retained earnings			28,584	934
Other equity interest			42,165	1,377
Deferred tax liabilities			8,636	282
Financial assets at fair value through other comprehensive income, category [member] \| IAS 39 [member]
Disclosure of financial assets [Line Items]
Available-for-sale financial assets			9,950	325
Financial assets at fair value through other comprehensive income, category [member] \| IFRS 9 [member]
Disclosure of financial assets [Line Items]
Available-for-sale financial assets			89,335	2,918
Financial assets at fair value through profit or loss, category [member] \| Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of financial assets [Line Items]
Retained earnings			493	16
Financial assets at fair value through profit or loss, category [member] \| IAS 39 [member]
Disclosure of financial assets [Line Items]
Available-for-sale financial assets			10,940	357
Financial assets at fair value through profit or loss, category [member] \| IFRS 9 [member]
Disclosure of financial assets [Line Items]
Available-for-sale financial assets			$ 11,433	$ 374

Effects on Initial Application of IFRS 9 and Information for the Years Ended December 31, 2016 and 2017 in Conformity With IAS 39 - Summary of Significant Accounts (Detail) $ in Thousands	Dec. 31, 2017 TWD ($)
Disclosure of financial assets [Line Items]
Available-for-sale financial assets	$ 20,890
Gross carrying amount [member]
Disclosure of financial assets [Line Items]
Available-for-sale financial assets	49,474
Allowance for impairment losses [member]
Disclosure of financial assets [Line Items]
Available-for-sale financial assets	$ (28,584)

Effects on Initial Application of IFRS 9 and Information for the Years Ended December 31, 2016 and 2017 in Conformity With IAS 39 - Aging of Accounts Receivable which are Past Due But Not Impaired (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)
Disclosure of financial assets that are either past due or impaired [line items]
Accounts and notes receivable	$ 4,747,288	$ 155,090	$ 4,015,734
Accounts receivable [member]
Disclosure of financial assets that are either past due or impaired [line items]
Accounts and notes receivable	4,747,834	155,108	4,013,705
Financial assets past due but not impaired [member] \| Accounts receivable [member]
Disclosure of financial assets that are either past due or impaired [line items]
Accounts and notes receivable			15,872
Within 1 month [member] \| Accounts receivable [member]
Disclosure of financial assets that are either past due or impaired [line items]
Accounts and notes receivable	18,807	615	10,482
Within 1 month [member] \| Financial assets past due but not impaired [member] \| Accounts receivable [member]
Disclosure of financial assets that are either past due or impaired [line items]
Accounts and notes receivable			10,482
1 - 2 months [member] \| Accounts receivable [member]
Disclosure of financial assets that are either past due or impaired [line items]
Accounts and notes receivable	131,787	4,305	477
1 - 2 months [member] \| Financial assets past due but not impaired [member] \| Accounts receivable [member]
Disclosure of financial assets that are either past due or impaired [line items]
Accounts and notes receivable			477
2 - 3 months [member] \| Accounts receivable [member]
Disclosure of financial assets that are either past due or impaired [line items]
Accounts and notes receivable	1,436	47	426
2 - 3 months [member] \| Financial assets past due but not impaired [member] \| Accounts receivable [member]
Disclosure of financial assets that are either past due or impaired [line items]
Accounts and notes receivable			426
3 - 4 months [member] \| Accounts receivable [member]
Disclosure of financial assets that are either past due or impaired [line items]
Accounts and notes receivable	180	6	1,431
3 - 4 months [member] \| Financial assets past due but not impaired [member] \| Accounts receivable [member]
Disclosure of financial assets that are either past due or impaired [line items]
Accounts and notes receivable			1,431
Over 4 months [member] \| Accounts receivable [member]
Disclosure of financial assets that are either past due or impaired [line items]
Accounts and notes receivable	$ 324	$ 11	3,056
Over 4 months [member] \| Financial assets past due but not impaired [member] \| Accounts receivable [member]
Disclosure of financial assets that are either past due or impaired [line items]
Accounts and notes receivable			$ 3,056

Effects on Initial Application of IFRS 9 and Information for the Years Ended December 31, 2016 and 2017 in Conformity With IAS 39 - Movements in Allowance for Impairment of Accounts and Other Receivables (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017 TWD ($)
Other receivables [member]
Disclosure of financial assets [Line Items]
Beginning balance	$ 0
Ending balance	0
Accounts receivable [member]
Disclosure of financial assets [Line Items]
Beginning balance	87
Reversal of allowance for impairment losses	$ (87)

Effects on Initial Application of IFRS 15 and Information for the Years Ended December 31, 2016 and 2017 in Conformity With IAS 18 - Impact and Description on Consolidated Statement of Financial Position and Statement of Comprehensive Income (Detail) $ / shares in Units, $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018 TWD ($) $ / shares	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)	Dec. 31, 2016 TWD ($)	Dec. 31, 2018 USD ($)
Disclosure of financial assets [Line Items]
Contract assets	$ 299,835				$ 9,795
Inventories	1,778,835		$ 1,929,239		58,113
Deferred tax assets	226,716		212,372		7,407
Contract liabilities	1,432				47
Receipts in advance	1,013		5,209		33
Current provisions	29,352		127,311		959
Retained earnings	3,602,663		2,815,966		$ 117,696
Revenue	18,480,027	$ 603,725	17,940,855	$ 18,387,593
Cost of revenue	(15,050,032)	(491,670)	(14,703,729)	(14,745,472)
Operating expenses	147,514	4,819	692,834	90,306
Other non-operating income (expenses), net	173,070	5,654	(310,691)	(147,948)
Income tax expense	456,618	14,918	550,487	177,120
Profit for the year	1,325,824	$ 43,313	$ 2,796,882	$ 1,401,210
IFRS 15 [member]
Disclosure of financial assets [Line Items]
Contract assets	299,835
Inventories	1,778,835
Deferred tax assets	226,716
Contract liabilities	1,432
Receipts in advance	1,013
Current provisions	29,352
Current refund liabilities	32,627
Retained earnings	3,602,663
Revenue	18,480,027
Cost of revenue	(15,050,032)
Operating expenses	(1,477,788)
Other non-operating income (expenses), net	173,070
Income tax expense	(456,618)
Profit for the year	$ 1,325,824
Earnings per share (in dollars)
Basic \| $ / shares	$ 1.65
Diluted \| $ / shares	$ 1.63
Previously stated [member]
Disclosure of financial assets [Line Items]
Inventories	$ 2,016,106
Deferred tax assets	226,635
Receipts in advance	2,445
Current provisions	61,979
Retained earnings	3,540,018
Revenue	18,434,763
Cost of revenue	(15,021,266)
Operating expenses	(1,477,653)
Other non-operating income (expenses), net	173,476
Income tax expense	(465,392)
Profit for the year	$ 1,301,093
Earnings per share (in dollars)
Basic \| $ / shares	$ 1.62
Diluted \| $ / shares	$ 1.60
Increase (decrease) due to changes in accounting policy [member]
Disclosure of financial assets [Line Items]
Contract assets	$ 299,835
Inventories	(237,271)
Deferred tax assets	81
Contract liabilities	1,432
Receipts in advance	(1,432)
Current provisions	(32,627)
Current refund liabilities	32,627
Retained earnings	62,645
Revenue	45,264
Cost of revenue	(28,766)
Operating expenses	(135)
Other non-operating income (expenses), net	(406)
Income tax expense	8,774
Profit for the year	$ 24,731
Earnings per share (in dollars)
Basic \| $ / shares	$ 0.03
Diluted \| $ / shares	$ 0.03

Effects on Initial Application of IFRS 15 and Information for the Years Ended December 31, 2016 and 2017 in Conformity With IAS 18 - Additional Information (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)	Dec. 31, 2016 TWD ($)	Dec. 31, 2018 USD ($)	Jan. 01, 2018 TWD ($)	Jan. 01, 2018 USD ($)
Disclosure of initial application of standards or interpretations [line items]
Retained earnings	$ 3,602,663		$ 2,815,966		$ 117,696
Inventories	1,778,835		1,929,239		58,113
Contract assets	299,835				9,795
Provision for sales allowance	29,352		127,311		959
Deferred tax assets	226,716		212,372		7,407
Deferred tax liabilities	308,759		174,293		10,087
Revenue	18,480,027	$ 603,725	17,940,855	$ 18,387,593
Cost of revenue	15,050,032	491,670	14,703,729	14,745,472
Income tax expense	456,618	14,918	$ 550,487	$ 177,120
Contract liabilities	1,432				47
Increase (decrease) due to application of IFRS 15 [member]
Disclosure of initial application of standards or interpretations [line items]
Retained earnings						$ (8,693)	$ (284)
Inventories	(237,271)				(7,751)
Contract assets	300,376				9,813
Provision for sales allowance	32,627				1,066	70,156	2,292
Deferred tax assets	81				3	(626)	(20)
Deferred tax liabilities						8,067	264
Revenue	300,376	9,813
Cost of revenue	237,271	7,751
Expected credit loss	135	4
Foreign exchange loss	406	13
Income tax expense	(81)	$ (3)
Contract liabilities	$ 1,432				$ 47
Increase (decrease) due to application of IFRS 15 [member] \| Customized products [member]
Disclosure of initial application of standards or interpretations [line items]
Retained earnings						46,607	1,523
Inventories						(208,505)	(6,812)
Contract assets						$ 255,112	$ 8,334

Translation into U.S. Dollar Amounts - Additional Information (Detail)	Dec. 31, 2018 $ / $
Foreign exchange rates [abstract]
Foreign exchange rate from New Taiwan dollars to U.S. dollars at the noon buying rate in the City of New York for cable transfers as certified for customs purposes by the Federal Reserve Bank of New York	30.61

Dividend - Additional Information (Detail) $ / shares in Units, $ in Thousands, $ in Thousands	Oct. 31, 2018 TWD ($)	Oct. 31, 2018 USD ($)	Jun. 26, 2018 $ / shares	Jul. 12, 2017 TWD ($)	May 26, 2017 $ / shares
Disclosure of dividends [Line Items]
Dividend paid			$ 0.30		$ 1.00
Dividend paid	$ 256,806	$ 8,390		$ 856,754
Capital surplus [member]
Disclosure of dividends [Line Items]
Dividend paid					$ 0.70

Segment Information - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2018 TWD ($)
Disclosure of major customers [abstract]
Revenue recognized in current reporting period related to carried-forward contract liabilities	$ 1,013

Non-current Financial Assets at Fair Value Through Other Comprehensive Income - Summary Amounts recognized in other comprehensive income in relation to the financial assets at fair value through other comprehensive income (Detail) - 12 months ended Dec. 31, 2018 $ in Thousands, $ in Thousands	TWD ($)	USD ($)
Financial assets at fair value through other comprehensive income [abstract]
Foreign unlisted stocks	$ 85,022	$ 2,778

Cash and Cash Equivalents - Additional Information (Detail) - TWD ($)	Dec. 31, 2018	Dec. 31, 2017
Cash and cash equivalents [abstract]
Cash and cash equivalents pledge	$ 0	$ 0

Capital Surplus and Retained Earnings - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2018
Disclosure of reserves within equity [abstract]
Maximum percentage of capital surplus to paid-in-capital required by the ROC Securities and Exchange Act	10.00%
Percentage of income transferred to legal reserve	10.00%
Threshold percentage over capital stock to be distributed out of legal reserve	25.00%

Significant Commitments and Contingencies - Capital Expenditures that are Contracted for, but not Provided for (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)
Disclosure of detailed information about property, plant and equipment [abstract]
Property plant and equipment, Contracted capital expenditures	$ 2,508,797	$ 81,960	$ 2,178,262

Supplementary Cash Flow Information - Partial Cash Paid for Investing and Financing Activities (Parenthetical) (Detail) - TWD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Disclosure Of Supplementary Cash Flow Information [line items]
Ending balance of other payables will be payable in 2018		$ (64,393)
Unimos Shanghai [member]
Disclosure Of Supplementary Cash Flow Information [line items]
Ending balance of other payables will be payable in 2018	$ 64,393

Financial Risk Management and Fair Values of Financial Instruments - Summary of Investments Financial Assets At Amortized Cost (Detail) - Dec. 31, 2018 $ in Thousands, $ in Thousands	TWD ($)	USD ($)
Disclosure of fair value financial assets amortised cost [line items]
Financial assets at amortized cost Bank deposits	$ 268,271	$ 8,763
Twelve months [member]
Disclosure of fair value financial assets amortised cost [line items]
Financial assets at amortized cost Bank deposits	$ 268,271

Financial Statements Schedule: Valuation and Qualifying Accounts (Parenthetical) (Detail) - Loss allowance for accounts receivable [member] - TWD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Disclosure of details of valuation and qualifying accounts [Line Items]
Loss allowance for accounts receivable	$ 2,141	$ 1,819
Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of details of valuation and qualifying accounts [Line Items]
Loss allowance for accounts receivable	$ 1,819