ASE Technology Holding (ASX) 20-F 6 Apr 21 2020 FY Annual report (foreign) Financial data

Cover Page

Cover Page	12 Months Ended
	Dec. 31, 2020shares
Cover [Abstract]
Document Type	20-F
Amendment Flag	false
Document Period End Date	Dec. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Trading Symbol	ASX
Entity Registrant Name	ASE Technology Holding Co., Ltd.
Entity Central Index Key	0001122411
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Shell Company	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding	4,350,675,482
Document Annual Report	true
Document Transition Report	false
Document Shell Company Report	false
Document Registration Statement	false
Title of 12(b) Security	Common Shares
Entity Interactive Data Current	Yes
Entity Voluntary Filers	No
Entity Address, Country	TW
ICFR Auditor Attestation Flag	true

Consolidated Balance Sheets

Consolidated Balance Sheets $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
CURRENT ASSETS
Cash and cash equivalents	$ 51,538,071	$ 1,835,401	$ 60,130,875
Financial assets at fair value through profit or loss - current	4,342,605	154,651	4,127,566
Contract assets - current	4,782,904	170,331	5,897,316
Trade receivables, net	91,833,989	3,270,441	78,948,473
Other receivables	3,693,936	131,551	1,293,819
Current tax assets	702,820	25,029	553,092
Inventories	48,516,459	1,727,794	33,883,750
Inventories related to real estate business	13,471,645	479,760	11,416,726
Other financial assets - current	551,655	19,646	765,834
Other current assets	4,578,783	163,062	4,983,667
Total current assets	224,012,867	7,977,666	202,001,118
NON-CURRENT ASSETS
Financial assets at fair value through profit or loss - non-current	1,793,188	63,860	1,161,430
Financial assets at fair value through other comprehensive income - non-current	1,741,134	62,006	1,770,775
Investments accounted for using the equity method	12,806,673	456,078	12,085,207
Property, plant and equipment	233,207,324	8,305,104	232,093,327
Right-of-use assets	8,620,612	307,002	9,792,221
Investment properties	12,538,083	446,513	12,854,071
Goodwill	54,777,439	1,950,764	50,198,436
Other intangible assets	26,808,668	954,725	29,024,392
Deferred tax assets	5,477,373	195,063	4,707,704
Other financial assets - non-current	530,345	18,887	559,493
Other non-current assets	1,263,188	44,985	975,532
Total non-current assets	359,564,027	12,804,987	355,222,588
Total assets	583,576,894	20,782,653	557,223,706
CURRENT LIABILITIES
Short-term borrowings	31,290,839	1,114,346	37,339,028
Financial liabilities at fair value through profit or loss - current	1,537,208	54,744	973,571
Financial liabilities for hedging - current	5,277,325	187,939	3,233,301
Trade payables	73,268,234	2,609,268	56,065,639
Other payables	39,415,623	1,403,690	39,181,690
Current tax liabilities	6,514,502	231,998	4,858,578
Lease liabilities - current	774,444	27,580	632,802
Current portion of bonds payable	6,999,951	249,286	250,000
Current portion of long-term borrowings	2,250,121	80,133	5,112,768
Other current liabilities	7,264,084	258,692	6,652,925
Total current liabilities	174,592,331	6,217,676	154,300,302
NON-CURRENT LIABILITIES
Financial liabilities for hedging - non-current	5,910,919	210,503
Bonds payable	49,253,603	1,754,046	36,272,155
Long-term borrowings	102,259,378	3,641,716	135,965,830
Deferred tax liabilities	6,551,233	233,306	5,772,237
Lease liabilities - non-current	5,101,386	181,673	5,176,123
Net defined benefit liabilities	6,466,794	230,299	5,254,401
Other non-current liabilities	1,710,090	60,900	1,680,346
Total non-current liabilities	177,253,403	6,312,443	190,121,092
Total liabilities	351,845,734	12,530,119	344,421,394
Share capital
Ordinary shares	43,385,311	1,545,061	43,254,026
Shares subscribed in advance	130,609	4,651	51,261
Total share capital	43,515,920	1,549,712	43,305,287
Capital surplus	139,767,550	4,977,477	138,910,363
Retained earnings
Legal reserve	3,901,384	138,938	2,203,895
Special reserve	10,847,697	386,314	6,902,782
Unappropriated earnings	30,084,965	1,071,402	21,029,962
Total retained earnings	44,834,046	1,596,654	30,136,639
Other equity	(10,043,302)	(357,667)	(10,965,782)
Treasury shares	(1,959,107)	(69,769)	(1,959,107)
Equity attributable to owners of the Company	216,115,107	7,696,407	199,427,400
NON-CONTROLLING INTERESTS	15,616,053	556,127	13,374,912
Total equity	231,731,160	8,252,534	212,802,312
TOTAL	$ 583,576,894	$ 20,782,653	$ 557,223,706

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)$ / shares	Dec. 31, 2020USD ($)$ / shares	Dec. 31, 2019TWD ($)$ / shares	Dec. 31, 2018TWD ($)$ / shares
Statement [LineItems]
OPERATING REVENUES	$ 476,978,710	$ 16,986,421	$ 413,182,184	$ 371,092,421
OPERATING COSTS	398,994,442	14,209,204	348,871,391	309,929,371
GROSS PROFIT	77,984,268	2,777,217	64,310,793	61,163,050
OPERATING EXPENSES
Selling and marketing expenses	5,605,464	199,625	5,751,168	4,933,602
General and administrative expenses	18,200,304	648,159	16,637,887	14,618,900
Research and development expenses	19,302,418	687,408	18,395,334	14,962,799
Total operating expenses	43,108,186	1,535,192	40,784,389	34,515,301
OTHER OPERATING INCOME AND EXPENSES, NET	502,492	17,895	(268,555)	371,583
PROFIT FROM OPERATIONS	35,378,574	1,259,920	23,257,849	27,019,332
NON-OPERATING INCOME AND EXPENSES
Other income	1,474,547	52,512	1,359,093	1,092,558
Other gains and losses	1,827,576	65,085	2,683,989	7,874,273
Finance costs	(3,459,511)	(123,202)	(4,203,395)	(3,568,241)
Share of the profit or loss of associates and joint ventures	547,612	19,502	182,275	(480,244)
Total non-operating income and expenses	390,224	13,897	21,962	4,918,346
PROFIT BEFORE INCOME TAX	35,768,798	1,273,817	23,279,811	31,937,678
INCOME TAX EXPENSE	7,116,898	253,451	5,011,246	4,513,369
PROFIT FOR THE YEAR	28,651,900	1,020,366	18,268,565	27,424,309
Items that will not be reclassified subsequently to profit or loss:
Remeasurement of defined benefit obligation	(594,778)	(21,181)	(365,262)	(308,180)
Unrealized loss on equity instruments at fair value through other comprehensive income	(166,239)	(5,920)	(216,121)	(422,441)
Share of other comprehensive income (loss) of associates and joint ventures	2,656,966	94,621	1,504,760	(558,217)
Income tax relating to items that will not be reclassified subsequently to profit or loss	(122,901)	(4,377)	(3,816)	134,853
Items that will not be reclassified subsequently to profit or loss	1,773,048	63,143	919,561	(1,153,985)
Items that may be reclassified subsequently to profit or loss:
Exchange differences on translating foreign operations	(831,784)	(29,622)	(5,202,145)	227,821
Unrealized loss on investments in debt instruments at fair value through other comprehensive income	(2,136)	(76)	(2,052)	(63,076)
Loss on hedging instruments	(574,824)	(20,471)
Share of other comprehensive income (loss) of associates and joint ventures	131,009	4,666	(85,975)	136,608
Items that may be reclassified subsequently to profit or loss	(1,277,735)	(45,503)	(5,290,172)	301,353
Other comprehensive income (loss) for the year, net of income tax	495,313	17,640	(4,370,611)	(852,632)
TOTAL COMPREHENSIVE INCOME FOR THE YEAR	29,147,213	1,038,006	13,897,954	26,571,677
PROFIT FOR THE YEAR ATTRIBUTABLE TO:
Owners of the Company	26,970,580	960,490	17,060,591	26,220,721
Non-controlling interests	1,681,320	59,876	1,207,974	1,203,588
PROFIT FOR THE YEAR	28,651,900	1,020,366	18,268,565	27,424,309
TOTAL COMPREHENSIVE INCOME FOR THE YEAR ATTRIBUTABLE TO:
Owners of the Company	27,440,726	977,234	13,122,185	25,620,461
Non-controlling interests	1,706,487	60,772	775,769	951,216
TOTAL COMPREHENSIVE INCOME FOR THE YEAR	$ 29,147,213	$ 1,038,006	$ 13,897,954	$ 26,571,677
EARNINGS PER SHARE
Basic | (per share)	$ 6.32	$ 0.23	$ 4.01	$ 6.18
Diluted | (per share)	6.17	0.22	3.91	6.07
American depositary shares [member]
EARNINGS PER SHARE
Basic | (per share)	12.65	0.45	8.02	12.35
Diluted | (per share)	$ 12.33	$ 0.44	$ 7.82	$ 12.14

Consolidated Statements of Chan

Consolidated Statements of Changes in Equity shares in Thousands, $ in Thousands, $ in Thousands	TWD ($)	USD ($)	Share capital [member]TWD ($)shares	Share capital [member]USD ($)shares	Capital surplus [member]TWD ($)	Capital surplus [member]USD ($)	Legal reserve [member]TWD ($)	Legal reserve [member]USD ($)	Special reserve [member]TWD ($)	Special reserve [member]USD ($)	Unappropriated earnings [member]TWD ($)	Unappropriated earnings [member]USD ($)	Retained earnings [member]TWD ($)	Retained earnings [member]USD ($)	Exchange differences on translating foreign operations [member]TWD ($)	Exchange differences on translating foreign operations [member]USD ($)	Unrealized gain (loss) on available-for-sale financial assets [member]TWD ($)	Unrealized gain (loss) on financial assets at fair value through other comprehensive income [member]TWD ($)	Unrealized gain (loss) on financial assets at fair value through other comprehensive income [member]USD ($)	Gain loss on hedging instrument [Member]TWD ($)	Gain loss on hedging instrument [Member]USD ($)	Other equity[member]TWD ($)	Other equity[member]USD ($)	Treasury shares [member]TWD ($)	Treasury shares [member]USD ($)	Equity Attributable to Owners of the Company [member]TWD ($)	Equity Attributable to Owners of the Company [member]USD ($)	Non-controlling interests [member]TWD ($)	Non-controlling interests [member]USD ($)
Balance at January 1 (Adjusted Balance [member]) at Dec. 31, 2017	$ 201,914,633		$ 87,380,787		$ 40,624,328		$ 16,765,066		$ 3,353,938		$ 54,485,857		$ 74,604,861		$ (6,733,659)		$ 135,517	$ 0				$ (6,598,142)		$ (7,292,513)		$ 188,719,321		$ 13,195,312
Balance at January 1 at Dec. 31, 2017															(6,733,659)													13,195,312
Beginning balance, shares at Dec. 31, 2017 | shares			8,738,079	8,738,079
Appropriation of earnings
Appropriated retained earnings	16,559,193						2,203,895		3,548,844
Change from investments in associates accounted for using the equity method	1,500,100				1,411,899						88,201		88,201													1,500,100
Cash dividends paid from the capital surplus	(10,795,980)				(10,795,980)																					(10,795,980)
Other changes in the capital surplus	872				872																					872
Net profit for the year	27,424,309										26,220,721		26,220,721													26,220,721		1,203,588
Other comprehensive income (loss) for the year, net of income tax	(852,632)										(146,194)		(146,194)		562,794		(1,016,860)					(454,066)				(600,260)		(252,372)
Total comprehensive income (loss)	26,571,677										26,074,527		26,074,527		562,794		(1,016,860)					(454,066)				25,620,461		951,216
Effect of the joint share exchange			$ (43,183,919)		117,693,658		(16,765,066)				(57,744,673)		(74,509,739)
Effect of the joint share exchange, shares | shares			(4,318,392)	(4,318,392)
Buy-back of ordinary shares	(71,302)																							(71,302)		(71,302)
Cancellation of treasury shares			$ (1,218,520)		(1,480,903)						(2,705,285)		(2,705,285)											5,404,708
Cash dividends received by subsidiaries from the Company	182,354				182,354																					182,354
Disposal of interest in associates and joint ventures accounted for using the equity method	(1,055,118)				(1,408,495)						204,450		204,450		282,291		(133,364)					148,927				(1,055,118)
Cancellation of treasury shares, shares | shares			(121,852)	(121,852)
Differences between consideration and carrying amount arising from acquisition or disposal of subsidiaries	1,640,159				(1,142,856)																					(1,142,856)		2,783,015
Changes in percentage of ownership interest in subsidiaries	(1,919,986)				(1,118,102)																					(1,118,102)		(801,884)
Issue of ordinary shares under employee share options	788,141	$ 23,879	$ 238,796		549,345																					788,141
Cash dividends distributed by subsidiaries	(424,815)																											(424,815)
Additional non-controlling interest arising on issue of employee share options by subsidiaries	697,187				(1,239,456)																					(1,239,456)		1,936,643
Disposal of investments in equity instruments at fair value through other comprehensive income											400		400				(400)					(400)
Balance at December 31 at Dec. 31, 2018	219,027,922		$ 43,217,144		143,276,664				3,353,938		20,403,477		23,757,415		(5,888,574)		(1,015,107)					(6,903,681)		(1,959,107)		201,388,435		17,639,487
Ending balance, shares at Dec. 31, 2018 | shares			4,321,714	4,321,714
Appropriation of earnings
Legal reserve							2,203,895				(2,203,895)
Special reserve									3,548,844		(3,548,844)
Cash dividends distributed by the Company	(10,806,454)										(10,806,454)		(10,806,454)													(10,806,454)
Appropriated retained earnings	14,310,735						1,697,489		3,944,915
Change from investments in associates accounted for using the equity method	3,604				3,604																					3,604
Other changes in the capital surplus	1,070				1,070																					1,070
Net profit for the year	18,268,565										17,060,591		17,060,591													17,060,591		1,207,974
Other comprehensive income (loss) for the year, net of income tax	(4,370,611)										(280,461)		(280,461)		(4,874,110)		1,216,165					(3,657,945)				(3,938,406)		(432,205)
Total comprehensive income (loss)	13,897,954										16,780,130		16,780,130		(4,874,110)		1,216,165					(3,657,945)				13,122,185		775,769
Issue of ordinary shares for capital increase by cash	(10,806,454)						2,203,895		3,548,844		(16,559,193)		(10,806,454)													(10,806,454)
Cash dividends received by subsidiaries from the Company	182,354				182,354																					182,354
Disposal of interest in investments accounted for using the equity method	(73,884)				(75,276)						1,392		1,392													(73,884)
Differences between consideration and carrying amount arising from acquisition or disposal of subsidiaries	(7,114,703)				(2,779,613)																					(2,779,613)		(4,335,090)
Changes in percentage of ownership interest in subsidiaries	(3,977,486)				(1,960,167)																					(1,960,167)		(2,017,319)
Issue of ordinary shares under employee share options	1,225,163		$ 88,143	$ 8,814	1,137,020																					1,225,163
Cash dividends distributed by subsidiaries	(360,245)																											(360,245)
Additional non-controlling interest arising on issue of employee share options by subsidiaries	797,017				(875,293)																					(875,293)		1,672,310
Disposal of investments in equity instruments at fair value through other comprehensive income											404,156		404,156					(404,156)				(404,156)
Balance at December 31 at Dec. 31, 2019	212,802,312		$ 43,305,287		138,910,363		2,203,895		6,902,782		21,029,962		30,136,639		(10,762,684)	$ (383,286)		(203,098)				(10,965,782)		(1,959,107)		199,427,400		13,374,912	$ 476,315
Ending balance, shares at Dec. 31, 2019 | shares			4,330,528	4,330,528
Appropriation of earnings
Legal reserve							1,697,489				(1,697,489)
Special reserve									3,944,915		(3,944,915)
Cash dividends distributed by the Company	(8,668,331)										(8,668,331)		(8,668,331)													(8,668,331)
Appropriated retained earnings	(8,668,331)						1,697,489		3,944,915		(14,310,735)		(8,668,331)													(8,668,331)
Change from investments in associates accounted for using the equity method	22,774				22,774																					22,774
Other changes in the capital surplus	1,608				1,608																					1,608		0
Net profit for the year	28,651,900	1,020,366									26,970,580		26,970,580													26,970,580		1,681,320
Other comprehensive income (loss) for the year, net of income tax	495,313	17,640									(469,748)		(469,748)		(879,255)			2,248,414		$ (429,265)		939,894				470,146		25,167
Total comprehensive income (loss)	29,147,213	1,038,006									26,500,832		26,500,832		(879,255)			2,248,414		(429,265)		939,894				27,440,726		1,706,487
Cash dividends received by subsidiaries from the Company					145,741																					145,741
Disposal of interest in investments accounted for using the equity method	2,313				2,199						(980)		(980)					1,094				1,094				2,313
Differences between consideration and carrying amount arising from acquisition or disposal of subsidiaries	(135,898)				(13,502)																					(13,502)		(122,396)
Changes in percentage of ownership interest in subsidiaries	(4,128,788)				(780,533)						(2,760,175)		(2,760,175)													(3,540,708)		(588,080)
Issue of ordinary shares under employee share options	1,799,425		$ 21,064	$ 210,633	1,588,792																					1,799,425
Cash dividends distributed by subsidiaries	(346,774)																											(346,774)
Additional non-controlling interest arising on issue of employee share options by subsidiaries	1,089,565				(109,892)						(392,447)		(392,447)													(502,339)		1,591,904
Disposal of investments in equity instruments at fair value through other comprehensive income											18,508		18,508					$ (18,508)				(18,508)
Balance at December 31 at Dec. 31, 2020	$ 231,731,160	$ 8,252,534	$ 43,515,920	$ 1,549,712	$ 139,767,550	$ 4,977,477	$ 3,901,384	$ 138,938	$ 10,847,697	$ 386,314	$ 30,084,965	$ 1,071,402	$ 44,834,046	$ 1,596,654	$ (11,641,939)	$ (414,599)	$ 2,027,902		$ 72,219	$ (429,265)	$ (15,287)	$ (10,043,302)	$ (357,667)	$ (1,959,107)	$ (69,769)	$ 216,115,107	$ 7,696,407	$ 15,616,053	$ 556,127
Ending balance, shares at Dec. 31, 2020 | shares			4,351,592	4,351,592

Consolidated Statements of Cash

Consolidated Statements of Cash Flows $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
CASH FLOWS FROM OPERATING ACTIVITIES
Profit before income tax	$ 35,768,798	$ 1,273,817	$ 23,279,811	$ 31,937,678
Adjustments for:
Depreciation expense	47,525,688	1,692,510	46,890,235	40,286,453
Amortization expense	3,733,377	132,955	3,576,606	2,402,450
Net loss (gain) on fair value change of financial assets and liabilities at fair value through profit or loss	71,848	2,559	(1,646,822)	(1,989,490)
Finance costs	3,459,511	123,202	4,203,395	3,568,241
Interest income	(520,783)	(18,546)	(549,681)	(466,211)
Dividend income	(150,715)	(5,367)	(185,061)	(190,397)
Share based compensations	955,575	34,030	871,699	215,648
Share of loss (profit) of associates and joint ventures	(547,612)	(19,502)	(182,275)	480,244
Loss (gain) on disposal of property, plant and equipment	(460,868)	(16,413)	164,467	56,902
Gain on disposal of investments accounted for using the equity method	(91,297)	(3,251)
Impairment loss recognized on financial assets			400,201	675,624
Reversal of impairment loss recognized on financial assets	(56,950)	(2,028)	(35,727)
Impairment loss recognized on non- financial assets	2,486,066	88,535	653,140	1,113,998
Gain on disposal of subsidiaries	(802,753)	(28,588)
Reversal of impairment loss recognized on non-financial assets				(100,000)
Gain on remeasurement of investments accounted for using the equity method			(319,712)	(7,421,408)
Net loss (gain) on foreign currency exchange	(2,543,821)	(90,592)	(1,498,107)	1,360,380
Others	(295,859)	(10,536)	8,687	1,142,735
Changes in operating assets and liabilities
Financial assets mandatorily at fair value through profit or loss	2,188,285	77,930	6,102,421	345,540
Contract assets	1,113,950	39,671	(1,408,816)	(508,166)
Trade receivables	(9,396,304)	(334,626)	995,839	(9,313,539)
Other receivables	(773,411)	(27,543)	(10,755)	443,517
Inventories	(13,559,192)	(482,877)	1,407,099	(9,249,714)
Other current assets	366,237	13,043	(1,206,456)	(385,172)
Other operating activities assets	(14,396)	(513)
Financial liabilities held for trading	(2,763,864)	(98,428)	(1,053,535)	(2,039,771)
Trade payables	14,032,779	499,743	(1,024,250)	6,989,198
Other payables	3,601,102	128,244	1,515,776	1,016,338
Other current liabilities	23,520	838	655,694	228,190
Other operating activities liabilities	(301,838)	(10,749)	267,965	(281,736)
Cash generated from operations	83,047,073	2,957,518	81,871,838	60,317,532
Interest received	479,900	17,090	549,846	523,679
Dividend received	512,287	18,244	518,115	297,882
Interest paid	(3,442,545)	(122,598)	(4,015,673)	(3,239,159)
Income tax paid	(5,536,077)	(197,154)	(6,620,876)	(6,825,243)
Net cash generated from operating activities	75,060,638	2,673,100	72,303,250	51,074,691
CASH FLOWS FROM INVESTING ACTIVITIES
Purchase of financial assets at fair value through other comprehensive income	(259,168)	(9,230)	(409,985)	(105,000)
Proceeds from sale of financial assets at fair value through other comprehensive income	20,686	737		94,217
Return of capital from financial assets at fair value through other comprehensive income	84,186	2,998	12,664	116,278
Purchase of financial assets at fair value through profit or loss			(26,852)
Acquisition of associates and joint ventures	(186,071)	(6,626)	(2,107,844)	(451,563)
Proceeds from disposal of investments accounted using the equity method	2,271,618	80,898
Net cash outflow on acquisition of subsidiaries	(8,745,638)	(311,454)	(81,646)	(95,241,855)
Proceeds from disposal of subsidiaries	3,717,039	132,373
Return of capital by investee accounted for using the equity method	125,005	4,452		262,941
Payments for property, plant and equipment	(62,077,446)	(2,210,735)	(56,810,153)	(41,386,443)
Proceeds from disposal of property, plant and equipment	4,449,113	158,444	448,939	1,127,644
Payments for intangible assets	(982,655)	(34,995)	(1,411,068)	(577,765)
Proceeds from disposal of intangible assets	8,353	297	6,929
Payments for right-of-use assets	(118,354)	(4,215)	(288,052)
Payments for investment properties	(6,352)	(226)	(2,532)	(125,764)
Proceeds from disposal of investment properties			5
Increase in other financial assets	(822,959)	(29,308)	(2,275,354)	(10,977,004)
Decrease in other financial assets	1,083,934	38,602	8,561,929	17,185,531
Increase in other non-current assets	(1,338,269)	(47,659)	(216,158)	(2,081,459)
Decrease in other non-current assets	1,244,650	44,325	20,032	110,687
Increase in financial liabilities for hedging				2,507,233
Proceeds from disposal of right-of-use assets	585,902	20,865
Other investing activities items	123	4	89
Net cash used in investing activities	(60,946,303)	(2,170,453)	(54,579,057)	(129,542,322)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from short-term borrowings				22,327,813
Repayment of short-term borrowings	(1,502,323)	(53,502)	(4,683,142)
Proceeds from bonds offering	19,967,149	711,081	19,279,033
Repayment of bonds payable	(250,000)	(8,903)		(6,185,600)
Proceeds from long-term borrowings	180,020,420	6,410,984	165,757,252	199,743,582
Repayment of long-term borrowings	(206,520,559)	(7,354,721)	(164,612,521)	(114,232,623)
Repayment of the principle portion of lease liabilities	(844,357)	(30,070)	(636,556)
Dividends paid	(8,520,982)	(303,454)	(10,623,030)	(10,613,626)
Proceeds from exercise of employee share options	1,934,530	68,894	1,149,227	1,269,680
Payments for buy-back of ordinary shares				(71,302)
Proceeds from disposal of interests in subsidiaries				2,807,568
Decrease in non-controlling interests	(6,291,089)	(224,042)	(12,117,251)	(11,820,227)
Other financing activities items	11,867	423	(11,820)	(113,859)
Net cash generated from (used in) financing activities	(21,995,344)	(783,310)	(6,498,808)	83,111,406
EFFECTS OF EXCHANGE RATE CHANGES ON THE BALANCE OF CASH AND CASH EQUIVALENTS HELD IN FOREIGN CURRENCY	(711,795)	(25,349)	(2,612,946)	796,595
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	(8,592,804)	(306,012)	8,612,439	5,440,370
CASH AND CASH EQUIVALENTS AT THE BEGINNING OF THE YEAR	60,130,875	2,141,413	51,518,436	46,078,066
CASH AND CASH EQUIVALENTS AT THE END OF THE YEAR	$ 51,538,071	$ 1,835,401	$ 60,130,875	$ 51,518,436

General Information

General Information	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
General Information	1. GENERAL INFORMATION ASE Technology Holding Co., Ltd. (the “Company”) is a corporation incorporated in Nanzih Technology Industrial Park (formerly known as Nantze Export Processing Zone) under the laws of Republic of China (“R.O.C.”) starting from April 30, 2018 (date of incorporation). The Company and its subsidiaries (collectively referred to as the “Group”) offer a comprehensive range of semiconductors packaging, testing, and electronic manufacturing services (“EMS”). The Company’s subsidiaries, Advanced Semiconductor Engineering, Inc. (symbol “2311”, “ASE”) and Siliconware Precision Industries Co., Ltd. (symbol “2325”, “SPIL”), entered into and executed a joint share exchange agreement to establish the Company and the Company acquired all issued and outstanding ordinary shares of ASE and SPIL on April 30, 2018. Both of ASE’s and SPIL’s ordinary shares have been delisted while the ordinary shares of the Company were listed starting from the same date under the symbol “3711”. In addition, ASE’s ordinary shares that have been traded on the New York Stock Exchange (the “NYSE”) under the symbol “ASX” in the form of American Depositary Shares (“ADS”) starting from September 2000 were exchanged as the Company’s ADSs under the same symbol “ASX” starting from April 30, 2018. The ordinary shares of the Company’s subsidiary, Universal Scientific Industrial (Shanghai) Co., Ltd. (“USISH”), have been listed on the Shanghai Stock Exchange under the symbol “601231” since February 2012. The consolidated financial statements are presented in the Company’s functional currency, New Taiwan dollar (NT$).

Approval of Financial Statement

Approval of Financial Statements	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Approval of Financial Statements	2. APPROVAL OF FINANCIAL STATEMENTS The consolidated financial statements were authorized for issue by the management on March 18, 2021.

Application of New and Revised

Application of New and Revised International Financial Reporting Standards as Issued by the International Accounting Standards Board ("IASB") ( Collectively, "IFRSs")	12 Months Ended
	Dec. 31, 2020
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Application of New and Revised International Financial Reporting Standards as Issued by the International Accounting Standards Board ("IASB") ( Collectively, "IFRSs")	3. APPLICATION OF NEW AND REVISED INTERNATIONAL FINANCIAL REPORTING STANDARDS AS ISSUED BY THE INTERNATIONAL ACCOUNTING STANDARDS BOARD (“IASB”) (collectively, “IFRSs”) a. Amendments to IFRSs that are mandatorily effective for the current year In the current year, the Group has applied the following new, revised or amended standards and interpretations that have been issued and effective: New, Revised or Amended Standards and Interpretations Effective Date Issued by IASB Amendments to IFRS 3 “Definition of a Business” January 1, 2020 Amendments to IFRS 9, IAS 39 and IFRS 7 “Interest Rate Benchmark Reform” January 1, 2020 Amendments to IAS 1 and IAS 8 “Definition of Material” January 1, 2020 New, Revised or Amended Standards and Interpretations Effective Date Issued by IASB Amendments to References to the Conceptual Framework in IFRS Standards January 1, 2020 Amendment to IFRS 16 “COVID-19-Related Rent Concessions” June 1, 2020 Except for the following, the initial application of the aforementioned new, revised or amended standards and interpretations did not have effect on the Group’s accounting policies: 1) Amendments to IFRS 3 “Definition of a Business” The Group applies the amendments to IFRS 3 to transactions that occur on or after January 1, 2020. The amendments clarify that to be considered a business, an acquired set of activities and assets must include, at a minimum, an input and a substantive process that together significantly contribute to the ability to create outputs. To determine whether an acquired process is substantive, different criteria apply, depending on whether there are outputs at the acquisition date. In addition, the amendments introduce an optional concentration test that permits a simplified assessment of whether or not an acquired set of activities and assets is a business. 2) Amendments to IFRS 9, IAS 39 and IFRS 7 “Interest Rate Benchmark Reform” Upon retrospective application of the amendments, the Group complied with the hedge accounting requirements under the assumption that the interest rate benchmark (such as the London Interbank Offered Rate or LIBOR) on which the hedged cash flows and cash flows from the hedging instrument are based will not be altered as a result of interest rate benchmark reform. 3) Amendments to IAS 1 and IAS 8 “Definition of Material” The Group adopted the amendments starting from January 1, 2020. The threshold of materiality that could influence users has been changed to “could reasonably be expected to influence”. Accordingly, disclosures in the consolidated financial statements do not include immaterial information that may obscure material information. 4) Amendment to IFRS 16 “COVID-19-Related Rent Concessions” The Group elected to apply the practical expedient provided in the amendment to IFRS 16 with respect to rent concessions negotiated with the lessor as a direct consequence of the COVID-19. The related accounting policies are stated in Note 4. Prior to the application of the amendment, the Group shall determine whether or not the abovementioned rent concessions need to be accounted for as lease modifications. The Group applied the amendment from January 1, 2020. Because the abovementioned rent concessions affected only in 2020, retrospective application of the amendment had no impact on the retained earnings as of January 1, 2020. b. New, revised or amended standards and interpretations in issue but not yet effective The Group has not applied the following new, revised or amended standards and interpretations that have been issued but are not yet effective: New, Revised or Amended Standards and Interpretations Effective Date Announced by IASB (Note 1) “Annual Improvements to IFRS Standards 2018–2020” January 1, 2022 (Note 2) Amendments to IFRS 3 “Reference to the Conceptual Framework” January 1, 2022 (Note 3) Amendments to IFRS 9, IAS 39, IFRS 7, IFRS 4 and IFRS 16 “Interest Rate Benchmark Reform - Phase 2” January 1, 2021 Amendments to IFRS 10 and IAS 28 “Sale or Contribution of Assets between an Investor and its Associate or Joint Venture” To be determined by IASB Amendments to IAS 1 “Classification of Liabilities as Current or Non-current” January 1, 2023 Amendments to IAS 1 “Disclosure of Accounting Policies” January 1, 2023 (Note 6) Amendments to IAS 8 “Definition of Accounting Estimates” January 1, 2023 (Note 7) Amendments to IAS 16 “Property, Plant and Equipment - Proceeds before Intended Use” January 1, 2022 (Note 4) Amendments to IAS 37 “Onerous Contracts–Cost of Fulfilling a Contract” January 1, 2022 (Note 5) Note 1: Unless stated otherwise, the above New IFRSs are effective for annual reporting periods beginning on or after their respective effective dates. Note 2: The amendments to IFRS 9 will be applied prospectively to modifications and exchanges of financial liabilities that occur on or after the annual reporting periods beginning on or after January 1, 2022. The amendments to IFRS 1 “First-time Adoptions of IFRSs” will be applied retrospectively for annual reporting periods beginning on or after January 1, 2022. Note 3: The amendments are applicable to business combinations for which the acquisition date is on or after the beginning of the annual reporting period beginning on or after January 1, 2022. Note 4: The amendments are applicable to property, plant and equipment that are brought to the location and condition necessary for them to be capable of operating in the manner intended by management on or after January 1, 2021. Note 5: The amendments are applicable to contracts for which the entity has not yet fulfilled all its obligations on January 1, 2022. Note 6: The amendments will be applied prospectively for annual reporting periods beginning on or after January 1, 2023. Note 7: The amendments are applicable to changes in accounting estimates and changes in accounting policies that occur on or after the beginning of the annual reporting period beginning on or after January 1, 2023. c. Significant changes in accounting policy resulted from new, revised and amended standards and interpretations in issue but not yet effective Except for the following, as of the date that the accompanying consolidated financial statements were authorized for issue, the Group continues evaluating the impact on its financial position and financial performance as a result of the initial application of the aforementioned new, revised or amended standards and interpretations. The related impact will be disclosed when the Group completes the evaluation. 1) Amendments to IAS 1 “Classification of Liabilities as Current or Non-current” The amendments clarify that for a liability to be classified as non-current, the Group shall assess whether it has the right at the end of the reporting period to defer settlement of the liability for at least twelve months after the reporting period. If such rights are in existence at the end of the reporting period, the liability is classified as non-current regardless of whether the Group will exercise that right. The amendments also clarify that, if the right to defer settlement is subject to compliance with specified conditions, the Group must comply with those conditions at the end of the reporting period even if the lender does not test compliance until a later date. The amendments stipulate that, for the purpose of liability classification, the aforementioned settlement refers to a transfer of cash, other economic resources or the Group’s own equity instruments to the counterparty that results in the extinguishment of the liability. However, if the terms of a liability that could, at the option of the counterparty, result in its settlement by a transfer of the Group’s own equity instruments, and if such option is recognized separately as equity in accordance with IAS 32 “Financial Instruments: Presentation”, the aforementioned terms would not affect the classification of the liability. 2) Amendments to IAS 16 “Property, Plant and Equipment: Proceeds before Intended Use” The amendments prohibit an entity from deducting from the cost of an item of property, plant and equipment any proceeds from selling items produced while bringing that asset to the location and condition necessary for it to be capable of operating in the manner intended by management. The cost of those items is measured in accordance with IAS 2 “Inventories”. Any proceeds from selling those items and the cost of those items are recognized in profit or loss in accordance with applicable standards. The amendments are applicable only to items of property, plant and equipment that are brought to the location and condition necessary for them to be capable of operating in the manner intended by management on or after January 1, 2021. 3) Amendments to IAS 37 “Onerous Contracts - Cost of Fulfilling a Contract” The amendments specify that when assessing whether a contract is onerous, the “cost of fulfilling a contract” includes both the incremental costs of fulfilling that contract (for example, direct labor and materials) and an allocation of other costs that relate directly to fulfilling contracts (for example, an allocation of depreciation for an item of property, plant and equipment used in fulfilling the contract). The Group will recognize the cumulative effect of the initial application of the amendments in the retained earnings at the date of the initial application. 4) Amendments to IAS 1 “Disclosure of Accounting Policies” The amendments specify that the Group should refer to the definition of material to determine its material accounting policy information to be disclosed. Accounting policy information is material if it can reasonably be expected to influence decisions that the primary users of general purpose financial statements make on the basis of those financial statements. The amendments also clarify that: • accounting policy information that relates to immaterial transactions, other events or conditions is immaterial and need not be disclosed; • the Group may consider the accounting policy information as material because of the nature of the related transactions, other events or conditions, even if the amounts are immaterial; and • not all accounting policy information relating to material transactions, other events or conditions is itself material. The amendments also illustrate that accounting policy information is likely to be considered as material to the financial statements if that information relates to material transactions, other events or conditions and: (1) the Group changed its accounting policy during the reporting period and this change resulted in a material change to the information in the financial statements; (2) the Group chose the accounting policy from options permitted by the standards; (3) the accounting policy was developed in accordance with IAS 8 “Accounting Policies, Changes in Accounting Estimates and Errors” in the absence of an IFRS that specifically applies; (4) the accounting policy relates to an area for which the Group is required to make significant judgments or assumptions in applying an accounting policy, and the Group discloses those judgments or assumptions; or (5) the accounting is complex and users of the financial statements would otherwise not understand those material transactions, other events or conditions. 5) Amendments to IAS 8 “Definition of Accounting Estimates” The amendments define that accounting estimates are monetary amounts in financial statements that are subject to measurement uncertainty. In applying accounting policies, the Group may be required to measure items at monetary amounts that cannot be observed directly and must instead be estimated. In such a case, the Group uses measurement techniques and inputs to develop accounting estimates to achieve the objective. The effects on an accounting estimate of a change in a measurement technique or a change in an input are changes in accounting estimates unless they result from the correction of prior period errors.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2020
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Summary of Significant Accounting Policies	4. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES a. Statement of compliance The consolidated financial statements have been prepared in accordance with IFRSs as issued by the IASB. b. Basis of preparation The consolidated financial statements have been prepared on the historical cost basis except for financial instruments measured at fair value and net defined benefit liabilities which are measured at the present value of the defined benefit obligation less the fair value of plan assets. The fair value measurements, which are grouped into Levels 1 to 3 based on the degree to which the fair value measurement inputs are observable and based on the significance of the inputs to the fair value measurement in its entirety, are described as follows: 1) Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities; 2) Level 2 inputs are inputs other than quoted prices included within Level 1 that are observable for an asset or a liability, either directly (i.e. as prices) or indirectly (i.e. derived from prices); and 3) Level 3 inputs are unobservable inputs for an asset or a liability. c. Classification of current and non-current assets and liabilities Current assets include cash and cash equivalents and those assets held primarily for trading purposes or expected to be realized within twelve months after the balance sheet date, unless the asset is to be used for an exchange or to settle a liability, or otherwise remains restricted, at more than twelve months after the balance sheet date. Current liabilities are obligations incurred for trading purposes or to be settled within twelve months after the balance sheet date (even if an agreement to refinance, or to reschedule payments, on a long-term basis is completed after the balance sheet date and before the consolidated financial statements are authorized for issue) and liabilities that do not have an unconditional right to defer settlement for at least 12 months after the balance sheet date (terms of a liability that could, at the option of the counterparty, result in its settlement by the issue of equity instruments do not affect its classification). Assets and liabilities that are not classified as current are classified as non-current. The Group engages in the construction business which has an operating cycle of over one year. The normal operating cycle applies when considering the classification of the Group’s construction-related assets and liabilities. d. Basis of consolidation 1) Principles for preparing consolidated financial statements The consolidated financial statements incorporate the financial statements of the Company and the entities controlled by the Company (i.e. its subsidiaries). Income and expenses of subsidiaries acquired or disposed of during the period are included in the consolidated statement of profit or loss and other comprehensive income from the effective dates of acquisitions up to the effective dates of disposals, as appropriate. When necessary, adjustments are made to the financial statements of subsidiaries to bring their accounting policies into line with those used by the Company. All intra-group transactions, balances, income and expenses are eliminated in full upon consolidation. Total comprehensive income of subsidiaries is attributed to the owners of the Company and to the non-controlling interests even if this results in the non-controlling interests having a deficit balance. 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 interests of the Group 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 the owners of the Company. When the Group loses control of a subsidiary, a gain or loss is recognized in profit or loss and is calculated as the difference between (i) the aggregate of the fair value of the consideration received and any investment retained in the former subsidiary at its fair value at the date when control is lost and (ii) the assets (including any goodwill) and liabilities and any non-controlling interests of the former subsidiary at their carrying amounts at the date when control is lost. The Group accounts for all amounts recognized in other comprehensive income in relation to that subsidiary on the same basis as would be required had the Group directly disposed of the related assets or liabilities. 2) Subsidiaries included in consolidated financial statements were as follows: Establishment Percentage of Ownership (%) and Operating December December Name of Investor Name of Investee Main Businesses Location 31, 2019 31, 2020 The Company ASE Engaged in the packaging and testing of semiconductors R.O.C. 100.0 100.0 USI Inc. (“USIINC”) Holding company R.O.C. 100.0 100.0 SPIL Engaged in the assembly, testing and turnkey services of integrated circuit R.O.C. 100.0 100.0 ASE A.S.E. Holding Limited Holding company Bermuda 100.0 100.0 J & R Holding Limited (“J&R Holding”) Holding company Bermuda 100.0 100.0 Innosource Limited Holding company British Virgin Islands 100.0 100.0 Omniquest Industrial Limited Holding company British Virgin Islands 71.0 71.0 ASE Marketing & Service Japan Co., Ltd. Engaged in marketing and sales services Japan 100.0 100.0 ASE Test, Inc. Engaged in the testing of semiconductors R.O.C. 100.0 100.0 Luchu Development Corporation Engaged in the development of real estate properties R.O.C. 67.1 67.1 ASE Embedded Electronics Inc. (“ASEEE”) Merged into ASE in February 2020 R.O.C. 100.0 - Advanced Microelectronic Products Inc. (“AMPI”) Engaged in the manufacturing of integrated circuit R.O.C. 7.6 7.6 ASE Test, Inc. Alto Enterprises Limited Holding company British Virgin Islands 100.0 100.0 Super Zone Holdings Limited Holding company Hong Kong 100.0 100.0 Luchu Development Corporation Engaged in the development of real estate properties R.O.C. 19.0 19.0 TLJ Intertech Inc. Engaged in information software services R.O.C. 60.0 60.0 MingFeng Information Service Corp., Ltd. Engaged in information software services R.O.C. 100.0 100.0 AMPI Engaged in the manufacturing of integrated circuit R.O.C. 43.4 43.4 A.S.E. Holding Limited ASE Investment (Labuan) Inc. Holding company Malaysia 70.1 70.1 ASE Test Limited (“ASE Test”) Holding company Singapore 10.2 10.2 J&R Holding ASE Test Holding company Singapore 89.8 89.8 Omniquest Industrial Limited Holding company British Virgin Islands 8.4 8.4 J&R Industrial Inc. Engaged in leasing equipment and investing activity R.O.C. 100.0 100.0 ASE Japan Co., Ltd. (“ASE Japan”) Engaged in the packaging and testing of semiconductors Japan 100.0 100.0 ASE (U.S.) Inc. After-sales service and sales support U.S.A. 100.0 100.0 Global Advanced Packaging Technology Limited Holding company British Cayman Islands 100.0 100.0 Anstock Limited Engaged in financing activity British Cayman Islands 100.0 100.0 Anstock II Limited Engaged in financing activity British Cayman Islands 100.0 100.0 Suzhou ASEN Semiconductors Co., Ltd. (“ASEN”) Engaged in the packaging and testing of semiconductors Suzhou, China 100.0 100.0 Innosource Limited Omniquest Industrial Limited Holding company British Virgin Islands 20.6 20.6 ASE (Shanghai) Inc. Engaged in the production of substrates Shanghai, China 8.5 8.5 Omniquest Industrial Limited ASE Corporation Holding company British Cayman Islands 100.0 100.0 Alto Enterprises Limited ASE (Kunshan) Inc. Engaged in the packaging and testing of semiconductors Kun Shan, China 22.9 22.9 ASE Investment (Kun Shan) Limited Holding company Kun Shan, China 85.9 85.9 Super Zone Holdings Limited Advanced Semiconductor Engineering (China) Ltd. Engaged in the packaging and testing of semiconductors Shanghai, China 100.0 100.0 ASE Investment (Labuan) Inc. ASE (Korea) Inc. (“ASE Korea”) Engaged in the packaging and testing of semiconductors Korea 100.0 100.0 ASE Korea ASE WeiHai Inc. Engaged in the packaging and testing of semiconductors Shandong, China 100.0 100.0 ASE Test ASE Test Holdings, Ltd. Holding company British Cayman Islands 100.0 100.0 ASE Holdings (Singapore) Pte Ltd Holding company Singapore 100.0 100.0 ASE Investment (Labuan) Inc. Holding company Malaysia 29.9 29.9 ASE Singapore Pte. Ltd. Engaged in the packaging and testing of semiconductors Singapore 100.0 100.0 ASE Test Holdings, Ltd. ISE Labs, Inc. Engaged in the testing of semiconductors U.S.A. 100.0 100.0 Establishment Percentage of Ownership (%) and Operating December December Name of Investor Name of Investee Main Businesses Location 31, 2019 31, 2020 ISE Labs, Inc. ISE Services, Inc. Engaged in wafer procurement and customer product management services and commenced operations in February 2020 U.S.A. - 100.0 ASE Holdings (Singapore) Pte Ltd ASE Electronics (M) Sdn. Bhd. Engaged in the packaging and testing of semiconductors Malaysia 100.0 100.0 Global Advanced Packaging Technology Limited ASE Assembly & Test (Shanghai) Limited (“ASESH”) Engaged in the packaging and testing of semiconductors Shanghai, China 100.0 100.0 ASE Advanced Semiconductor (Shanghai) Limited Engaged in the packaging and testing of semiconductors and was established and spun off from ASESH in November 2020 Shanghai, China - 100.0 ASESH ASE Investment (Kun Shan) Limited Holding company Kun Shan, China 14.1 14.1 Wuxi Tongzhi Microelectronics Co., Ltd. Engaged in the packaging and testing of semiconductors Wuxi, China 100.0 100.0 ISE Labs, China, Ltd. Engaged in the testing of semiconductor Shanghai, China 100.0 100.0 Shanghai Ding Hui Real Estate Development Co., Ltd. (“DH”) Engaged in the development, construction and sale of real estate properties Shanghai, China 60.0 60.0 DH Shanghai Ding Qi Property Management Co., Ltd. Engaged in the management of real estate properties Shanghai, China 100.0 100.0 Shanghai Ding Wei Real Estate Development Co., Ltd. (“DW”) Engaged in the development, construction and leasing of real estate properties Shanghai, China 100.0 100.0 Shanghai Ding Yu Real Estate Development Co., Ltd. Engaged in the development, construction and leasing of real estate properties Shanghai, China 100.0 100.0 Kun Shan Ding Hong Real Estate Development Co., Ltd Engaged in the development, construction and leasing of real estate properties Kun Shan, China 100.0 100.0 Shanghai Ding Xu Property Management Co., Ltd. Engaged in the management of real estate properties Shanghai, China 100.0 100.0 Shanghai Dingyao Estate Development Co., Ltd. Engaged in property management and was invested in April 2020 Shanghai, China - 100.0 Shanghai Ding Fan Business Management Co., Ltd. (The name was changed on June 2020 and the former name was Shanghai Ding Fan Department Store Co., Ltd.) Engaged in the management of real estate properties (acquired from DW in November 2020) Shanghai, China - 100.0 DW Shanghai Ding Fan Business Management Co., Ltd. (The name was changed on June 2020 and the former name was Shanghai Ding Fan Department Store Co., Ltd.) Engaged in leasing and management of real estate properties (disposed to DH in November 2020) Shanghai, China 100.0 - ASE Investment (Kun Shan) Limited ASE (Kunshan) Inc. Engaged in the packaging and testing of semiconductors Kun Shan, China 49.3 49.3 ASE Corporation ASE Mauritius Inc. Holding company Mauritius 100.0 100.0 ASE Labuan Inc. Holding company Malaysia 100.0 100.0 ASE Mauritius Inc. ASE (Kunshan) Inc. Engaged in the packaging and testing of semiconductors Kun Shan, China 27.8 27.8 ASE (Shanghai) Inc. Engaged in the production of substrates Shanghai, China 91.5 91.5 ASE Labuan Inc. ASE Electronics Inc. Engaged in the production of substrates R.O.C. 100.0 100.0 ASE (Shanghai) Inc. Advanced Semiconductor Engineering (HK) Limited Engaged in the trading of substrates Hong Kong 100.0 100.0 Shanghai Ding Hui Real Estate Development Co., Ltd. Engaged in the development, construction and sale of real estate properties Shanghai, China 40.0 40.0 Universal Scientific Industrial (Shanghai) Co., Ltd. (“USISH”) Engaged in the designing, manufacturing and sales of electronic components Shanghai, China 0.8 0.8 USIINC Huntington Holdings International Co., Ltd. Holding company British Virgin Islands 100.0 100.0 Huntington Holdings International Co., Ltd. Unitech Holdings International Co., Ltd. Holding company British Virgin Islands 100.0 100.0 Real Tech Holdings Limited Holding company British Virgin Islands 100.0 100.0 Universal ABIT Holding Co., Ltd. In the process of liquidation British Cayman Islands 100.0 100.0 Real Tech Holdings Limited Universal Scientific Industrial (Kunshan) Co., Ltd. Liquidated in June 2020 Kun Shan, China 100.0 - USI Enterprise Limited (“USIE”) Engaged in the service of investment advisory and warehousing management Hong Kong 95.8 95.9 USIE USISH Engaged in the designing, manufacturing and sales of electronic components Shanghai, China 77.7 76.6 USISH Universal Global Technology Co., Limited Holding company Hong Kong 100.0 100.0 Establishment Percentage of Ownership (%) and Operating December December Name of Investor Name of Investee Main Businesses Location 31, 2019 31, 2020 Universal Global Technology (Kunshan) Co., Ltd. (“UGKS”) Engaged in the designing and manufacturing of electronic components Kun Shan, China 100.0 100.0 Universal Global Technology (Shanghai) Co., Ltd. Engaged in the processing and sales of computer and communication peripherals as well as business in import and export of goods and technology Shanghai, China 100.0 100.0 Universal Global Electronics (Shanghai) Co., Ltd. Engaged in the sales of electronic components and telecommunications equipment Shanghai, China 100.0 100.0 USI Electronics (Shenzhen) Co., Ltd. Engaged in the design, manufacturing and sales of motherboards and computer peripherals Shenzhen, China 50.0 50.0 Huanrong Electronics (Huizhou) Co., Ltd. Engaged in the research and manufacturing of new electronic applications, communications, computers and other electronics products and also provided auxiliary technical services as well as import and export services (acquired from Universal Global Electronics (Shanghai) Co., Ltd. in November 2020) Huizhou, China - 100.0 FINANCIERE AFG (“ ） Holding company France - 10.4 Universal Global Technology Co., Limited Universal Global Industrial Co., Limited Engaged in manufacturing, trading and investing activity Hong Kong 100.0 100.0 Universal Global Scientific Industrial Co., Ltd. (“UGTW”) Engaged in the manufacturing of components of telecomm and cars and provision of related R&D services R.O.C. 100.0 100.0 USI America Inc. Engaged in the manufacturing and processing of motherboards and wireless network communication and provision of related technical service U.S.A. 100.0 100.0 Universal Scientific Industrial De Mexico S.A. De C.V. Engaged in the assembling of motherboards and computer components Mexico 100.0 100.0 USI Japan Co., Ltd. Engaged in the manufacturing and sales of computer peripherals, integrated chip and other related accessories Japan 100.0 100.0 USI Electronics (Shenzhen) Co., Ltd. Engaged in the design, manufacturing and sales of motherboards and computer peripherals Shenzhen, China 50.0 50.0 Universal Global Electronics Co., Ltd. Engaged in accepting and outsourcing orders as well as sales of electronic components and service of technical advisory Hong Kong 100.0 100.0 Universal Scientific Industrial (France) (“USIFR”) Engaged in investing activities and was established in August 2019 France 100.0 100.0 Universal Scientific Industrial Vietnam Company Limited Engaged in IC assembly for wearable devices and was established in July 2020. Vietnam - 100.0 Universal Global Industrial Co., Limited Universal Scientific Industrial De Mexico S.A. De C.V. Engaged in the assembling of motherboards and computer components Mexico (Note) (Note) UGTW Universal Scientific Industrial Co., Ltd. (“USI”) Engaged in the manufacturing, processing and sales of computers, computer peripherals and related accessories R.O.C. 100.0 100.0 USI Electronics (Shenzhen) Co., Ltd. Huanrong Electronics (Huizhou) Co., Ltd. Engaged in the research and manufacturing of new electronic applications, communications, computers and other electronics products and also provided auxiliary technical services as well as import and export services (disposed to USISH in November 2020) Huizhou, China 100.0 - Universal Global Electronics Co., Ltd. Semicondutores Avancados do Brasil S.A. Liquidated in December 2020 Brasil 75.0 - Universal Scientific Industrial Poland Sp. z o.o. (“USIPL”) (The name was changed on June 2020 and the former name was Chung Hong Electronics Poland Sp. z o.o.) Engaged in the design and manufacturing of electronic components and new electronic applications Poland 60.0 100.0 Universal Global Electronics (Shanghai) Co., Ltd. USI Science and Technology (Shenzhen) Co., Ltd. Engaged in the design of electronic components, service of technical advisory; wholesale of electronic components and communication peripherals as well as business in import and export of goods and management of properties and was established in November 2020. Shenzhen, China - 100.0 USIFR FAFG Holding company France - 89.6 ASTEELFLASH GROUP Holding company France - (Note) Establishment Percentage of Ownership (%) and Operating December December Name of Investor Name of Investee Main Businesses Location 31, 2019 31, 2020 FAFG ASTEELFLASH GROUP Holding company France - 100.0 MANUFACTURING POWER TUNISIA Engaged in the design and manufacturing of electronic components Tunisia 0.1 ASTEELFLASH MEXICO S.A. de C.V. Engaged in the design and manufacturing of electronic components Mexico 0.1 ASTEELFLASH GROUP ASTEELFLASH (BEDFORD) LIMITED Engaged in the design and manufacturing of electronic components United Kingdom - 100.0 ASTEELFLASH FRANCE Engaged in the design and manufacturing of electronic components France - 99.9 ASTEELFLASH TUNISIE S.A. Engaged in the design and manufacturing of electronic components Tunisia - 100.0 ASTEELFLASH HONG KONG LIMITED Holding company Hong Kong - 100.0 ASTEELFLASH MEXICO S.A. de C.V. Engaged in the design and manufacturing of electronic components Mexico - 99.9 ASTEELFLASH GERMANY GmbH Engaged in the design and manufacturing of electronic components Germany - 100.0 MANUFACTURING POWER TUNISIA Engaged in the design and manufacturing of electronic components Tunisia - 99.9 ASTEELFLASH US HOLDING CORP. Holding company U.S.A. - 100.0 ASTEEL ELECTRONIQUE FOUCHANA Engaged in the design and manufacturing of electronic components Tunisia - (Note) AFERH TUNISIE Engaged in the management, training and consulting of human resources Tunisia - 0.5 ASTEEL ELECTRONICS MANUFACTURING SERVICES Engaged in the design and manufacturing of electronic components Tunisia 0.1 ASTEELFLASH (BEDFORD) LIMITED ASTEELFLASH TUNISIE S.A. Engaged in the design and manufacturing of electronic components Tunisia - (Note) ASTEELFLASH TECHNOLOGIE ASTEELFLASH FRANCE Engaged in the design and manufacturing of electronic components France - (Note) ASTEELFLASH FRANCE SCI CHASSET Engaged in the management and operation of real estate properties and holding the ownership of real estate properties France - 100.0 AFERH Engaged in the management, training and consulting of human resources France - 100.0 ASTEEL ELECTRONICS MANUFACTURING SERVICES Engaged in the design and manufacturing of electronic components Tunisia - 99.9 ASTEEL ELECTRONIQUE FOUCHANA Engaged in the design and manufacturing of electronic components Tunisia - 94.2 ASTEELFLASH TECHNOLOGIE Engaged in projection of plastic and the design and manufacturing of industrial components France - 100.0 ASTEELFLASH BRETAGNE Engaged in the design and manufacturing of electronic components France - 100.0 ASTEELFLASH TUNISIE S.A. Engaged in the design and manufacturing of electronic components Tunisia - (Note) ASTEELFLASH TUNISIE S.A. ASTEEL ELECTRONIQUE TUNISIE Engaged in the design and manufacturing of electronic components Tunisia - 100.0 ASTEEL ELECTRONIQUE FOUCHANA Engaged in the design and manufacturing of electronic components Tunisia (Note) AFERH AFERH TUNISIE Engaged in the management, training and consulting of human resources Tunisia - 99.5 ASTEELFLASH HONG KONG LIMITED ASTEELFLASH SUZHOU CO., LTD. Engaged in the design and manufacturing of electronic components Suzhou, China - 100.0 ASTEELFLASH SUZHOU CO., LTD. ASTEEL ELECTRONIQUE FOUCHANA Engaged in the design and manufacturing of electronic components Tunisia - (Note) ASTEELFLASH TUNISIE S.A. Engaged in the design and manufacturing of electronic components Tunisia - (Note) ASTEELFLASH GERMANY GmbH ASTEELFLASH HERSFELD GmbH Engaged in the design and manufacturing of electronic components Germany - 100.0 ASTEELFLASH EBERBACH GmbH Engaged in the design and manufacturing of electronic components Germany - 100.0 ASTEELFLASH BONN GmbH Engaged in the design and manufacturing of electronic components Germany - 100.0 ASTEELFLASH SCHWANDORF GmbH Engaged in the design and manufacturing of electronic components Germany - 100.0 ASTEELFLASH PLZEN S.R.O. Engaged in the design and manufacturing of electronic components Czech Republic - 100.0 ASTEELFLASH DESIGN SOLUTIONS HAMBOURG GmbH Engaged in the design and manufacturing of electronic components Germany - 100.0 EN ELECTRONICNETWORK SRL Engaged in the design and manufacturing of electronic components Romania - 100.0 Establishment Percentage of Ownership (%) and Operating December December Name of Investor Name of Investee Main Businesses Location 31, 2019 31, 2020 ASTEELFLASH TUNISIE S.A. Engaged in the design and manufacturing of electronic components Tunisia - (Note) ASTEELFLASH MEXICO S.A. de C.V. ASTEELFLASH TUNISIE S.A. Engaged in the design and manufacturing of electronic components Tunisia - (Note) ASTEELFLASH US HOLDING CORP. ASTEELFLASH USA CORP. Engaged in the design and manufacturing of electronic components U.S.A. - 100.0 ASTEELFLASH USA CORP. ASTEEL ELECTRONIQUE FOUCHANA Engaged in the design and manufacturing of electronic components Tunisia - (Note) ASTEELFLASH TUNISIE S.A. Engaged in the design and manufacturing of electronic components Tunisia - (Note) SPIL SPIL (B.V.I.) Holding Limited Engaged in investing activities British Virgin Islands 100.0 100.0 Siliconware Investment Co., Ltd. Engaged in investing activities R.O.C. 100.0 100.0 SPIL (B.V.I.) Holding Limited Siliconware USA, Inc. Engaged in marketing activities U.S.A. 100.0 100.0 SPIL (Cayman) Holding Limited Engaged in investing activities British Cayman Islands 100.0 100.0 SPIL (Cayman) Holding Limited Siliconware Technology (Suzhou) Limited (“SZ”) Engaged in the packaging and testing of semiconductors Suzhou, China 100.0 100.0 Siliconware Electronics (Fujian) Co., Limited (“SF”) Engaged in the packaging and testing of semiconductors and was disposed in October 2020 (Note 30) Fujian, China 100.0 - Note: The number of shares held is 1 share or 3 shares and representing less than 0.1% of total shares. e. Business combination s Acquisitions of businesses are accounted for using the acquisition method. Acquisition-related costs are generally recognized in profit or loss as they are incurred. Goodwill is measured as the excess of the sum of the consideration transferred, the amount of any non-controlling interests in the acquiree, and the fair value of the acquirer’s previously held equity interest in the acquiree (if any) over the net of the acquisition-date amounts of the identifiable assets acquired and the liabilities assumed. If, after re-assessment, the net of the acquisition-date amounts of the identifiable assets acquired and liabilities assumed exceeds the sum of the consideration transferred, the amount of any non-controlling interests in the acquiree and the fair value of the acquirer’s previously held interest in the acquiree (if any), the excess is recognized immediately in profit or loss as a bargain purchase gain. Non-controlling interests that are present ownership interests and entitle their holders to a proportionate share of the entity’s net assets in the event of liquidation may be initially measured either at fair value or at the non-controlling interests’ proportionate share of the recognized amounts of the acquiree’s identifiable net assets. The choice of measurement is made on a transaction-by-transaction basis. Other types of non-controlling interests are measured at fair value. Where the consideration the Group transfers in a business combination includes assets or liabilities resulting from a contingent consideration arrangement, the contingent consideration is measured at its acquisition-date fair value and considered as part of the consideration transferred in a business combination. Changes in the fair value of the contingent consideration that qualify as measurement period adjustments are adjusted retrospectively, with the corresponding adjustments being made against goodwill or gains on bargain purchases. Measurement period adjustments are adjustments that arise from additional information obtained during the measurement period about facts and circumstances that existed as of the acquisition date. The measurement period does not exceed 1 year from the acquisition date. The subsequent accounting for changes in the fair value of the contingent consideration that do not qualify as measurement period adjustments depends on how the contingent consideration is classified. Contingent consideration not classified as equity is remeasured at fair value at the end of subsequent reporting period with any gain or loss recognized in profit or loss. When a business combination is achieved in stages, the Group’s previously held equity interest in an acquiree is remeasured to fair value at acquisition date, and the resulting gain or loss, if any, is recognized in profit or loss or other comprehensive income. Amounts arising from interests in the acquiree prior to the acquisition date that have previously been recognized in other comprehensive income are recognized on the same basis as would be required had those interest been directly disposed of by the Group. If the initial accounting for a business combination is incomplete by the end of the reporting period in which the combination occurs, the Group reports provisional amounts for the items for which the accounting is incomplete. Those provisional amounts are adjusted retrospectively during the measurement period, or additional assets or liabilities are recognized, to reflect new information obtained about facts and circumstances that existed at the acquisition date that, if known, would have affected the amounts recognized at that date. Business combination involving entities under common control is not accounted for using the acquisition method but is accounted for at the carrying amounts of the entities. The Group elected not to restate comparative information of the prior period in the financial statements as the business combination was an organization restructure under common control. f. Foreign currencies In preparing the financial statements of each individual entity, transactions in currencies other than the entity’s functional currency (i.e. foreign currencies) are recognized at the rates of exchange prevailing at the dates of the transactions. At each balance sheet date, monetary items denominated in foreign currencies are retranslated at the rates prevailing at that date. Exchange differences on monetary items arising from settlement or translation are recognized in profit or loss in the period in which they arise except for exchange differences on transactions entered into in order to hedge certain foreign currency risks. Non-monetary items denominated in foreign currencies that are measured at fair value are retranslated at the rates prevailing at the date when the fair value was determined. Exchange differences arising from the retranslation of non-monetary items are included in profit or loss for the period except for exchange differences arising from the retranslation of non-monetary items in respect of which gains and losses are recognized directly in other comprehensive income, in which cases, the exchange differences are also recognized directly in other comprehensive income. Non-monetary items denominated in a foreign currency and measured at historical cost are translated using the exchange rate at the date of the transaction, and are not retranslated. For the purposes of presenting the consolidated financial statements, the assets and liabilities of the Group’s foreign operations (including subsidiaries, associates and joint ventures in other countries that use currencies which are different from the currency of the Company) are translated into the New Taiwan dollars using exchange rates prevailing at each balance sheet date. Income and expense items are translated at the average exchange rates for the period. The resulting currency translation differences are recognized in other comprehensive income and accumulated in equity attributed to the owners of the Company and non-controlling interests as appropriate. On the disposal of the Group’s entire interest in a foreign operation, or a disposal involving the loss of control over a subsidiary that includes a foreign operation, or a partial disposal of an interest in a joint arrangement or an associate that includes a foreign operation of which the retained interest becomes a financial asset, all of the exchange differences accumulated in equity in respect of that operation attributable to the owners of the Company are reclassified to profit or loss. In relation to a partial disposal of a subsidiary that does not result in the Group losing control over the subsidiary, the proportionate share of accumulated exchange differences is re-attributed to the non-controlling interests of the subsidiary and is not recognized in profit or loss. For all other partial disposals, the proportionate share of the accumulated exchange differences recognized in other comprehensive income is reclassified to profit or loss. Goodwill and fair value adjustments recognized on identifiable assets and liabilities of acquired foreign operation are treated as assets and liabilities of the foreign operation and translated at the rates of exchange prevailing at the end of each reporting period. Exchange differences are recognized in other comprehensive income. g. Inventories and inventories related to real estate business Inventories, including raw materials (materials received from customers for processing, mainly semiconductor wafers, are excluded from inventories as title and risk of loss remain with the customers), supplies, work in process, finished goods, and materials and supplies in transit are stated at the lower of cost or net realizable value. Inventory write-downs are made by item, except for those that may be appropriate to group items of similar or related inventories. Net realizable value is the estimated selling prices of inventories less all estimated costs of completion and estimated costs necessary to make the sale. Raw materials and supplies are recorded at moving average cost while work in process and finished goods are recorded at standard cost. Inventories related to real estate business include land and buildings held for sale, land held for construction and construction in progress. Land held for development is recorded as land held for construction upon obtaining the title of ownership. Prior to the completion, the borrowing costs directly attributable to construction in progress are capitalized as part of the cost of the asset. Construction in progress is transferred to land and buildings held for sale upon completion. Land and buildings held for sale, construction in progress and land held for construction are stated at the lower of cost or net realizable value and related write-downs are made by item. The amounts received in advance for real estate properties are first recorded as advance receipts and then recognized as revenue when the construction is completed and the title and significant risk of the real estate properties are transferred to customers. Cost of sales of land and buildings held for sale are recognized based on the ratio of property sold to the total property developed. h. Investments in associates and joint ventures An associate is an entity over which the Group has significant influence and that is neither a subsidiary nor an interest in a joint venture. Joint venture is a j

Critical Accounting Judgments a

Critical Accounting Judgments and Key Sources of Estimation Uncertainty	12 Months Ended
	Dec. 31, 2020
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Critical Accounting Judgments and Key Sources of Estimation Uncertainty	5. CRITICAL ACCOUNTING JUDGMENTS AND KEY SOURCES OF ESTIMATION UNCERTAINTY In the application of the Group’s accounting policies, management is required to make judgments, estimates and assumptions about the carrying amounts of assets and liabilities that are not readily apparent from other sources. The estimates and underlying assumptions are based on historical experience and other factors that are considered to be relevant. Actual results may differ from these estimates. 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 period, or in the period of the revision and future periods if the revision affects both current and future periods. Impairment of goodwill Determining whether goodwill is impaired requires an estimation of the value in use of the cash-generating units to which goodwill has been allocated. The calculation of the value in use requires management to estimate the future cash flows expected to be generated from the cash-generating units and a suitable discount rate in order to calculate the present value. Where the actual future cash flows are less than expected, a material impairment loss may arise.

Cash and Cash Equivalents

Cash and Cash Equivalents	12 Months Ended
	Dec. 31, 2020
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Cash and Cash Equivalents	6. CASH AND CASH EQUIVALENTS December 31 2019 2020 NT$ NT$ US$ (Note 4) Cash on hand $ 6,567 $ 6,073 $ 216 Checking accounts and demand deposits 44,565,936 48,734,866 1,735,572 Cash equivalents Cash equivalents (time deposits with original maturity of less than three months) 15,558,372 2,797,132 99,613 $ 60,130,875 $ 51,538,071 $ 1,835,401

Financial Instruments at Fair V

Financial Instruments at Fair Value Through Profit or Loss	12 Months Ended
	Dec. 31, 2020
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Financial Instruments at Fair Value Through Profit or Loss	7. FINANCIAL INSTRUMENTS AT FAIR VALUE THROUGH PROFIT OR LOSS December 31 2019 2020 NT$ NT$ US$ (Note 4) Financial assets mandatorily classified as at FVTPL Derivative instruments (non-designated hedges) Forward exchange contracts $ 104,308 $ 122,511 $ 4,363 Swap contracts 56,561 99,312 3,537 Call option (Note 29) 24,556 - - Non-derivative financial assets Quoted ordinary shares $ 3,460,123 $ 4,064,438 $ 144,745 Private-placement funds 603,718 1,124,754 40,055 Unquoted preferred shares 377,440 385,440 13,726 Open-end mutual funds 662,290 339,338 12,085 5,288,996 6,135,793 218,511 Current 4,127,566 4,342,605 154,651 Non-current $ 1,161,430 $ 1,793,188 $ 63,860 Financial liabilities held for trading - current Derivative instruments (non-designated hedging) Swap contracts $ 862,581 $ 1,448,972 $ 51,602 Target redemption forward contracts - 79,216 2,821 Forward exchange contracts 110,990 9,020 321 $ 973,571 $ 1,537,208 $ 54,744 At each balance sheet date, outstanding s Notional Amount Currency Maturity Period (In Thousands) December 31, 2019 Sell NT$/Buy US$ 2020.01-2020.12 NT$50,241,799/US$1,660,000 Sell US$/Buy RMB 2020.02 US$49,666/RMB349,800 Sell US$/Buy JPY 2020.02-2020.03 US$45,878/JPY5,000,000 Sell US$/Buy KRW 2020.01 US$28,000/KRW32,454,800 Sell US$/Buy MYR 2020.01 US$11,000/MYR45,507 Sell US$/Buy NT$ 2020.01 US$189,960/NT$5,719,478 December 31, 2020 Sell NT$/Buy US$ 2021.01-2021.12 NT$51,140,082/US$1,755,000 Sell US$/Buy RMB 2021.01-2021.02 US$59,793/RMB395,742 Sell US$/Buy HKD 2021.02 US$13,804/HKD107,000 Sell US$/Buy JPY 2021.01 US$41,630/JPY4,300,000 Sell US$/Buy KRW 2021.01 US$30,000/KRW33,066,000 Sell US$/Buy NT$ 2021.01-2021.02 US$675,240/NT$19,073,846 At each balance sheet date, outstanding forward exchange contracts not accounted for hedge accounting were as follow: Notional Amount Currency Maturity Period (In Thousands) December 31, 2019 Sell RMB/Buy US$ 2020.01-2020.02 RMB2,224,491/US$316,896 Sell HKD/Buy US$ 2020.01 HKD1,705,281/US$218,297 Sell NT$/Buy US$ 2020.01 NT$2,275,860/US$75,000 Sell US$/Buy RMB 2020.01-2020.03 US$109,000/RMB767,277 Sell US$/Buy JPY 2020.01-2020.04 US$87,398/JPY9,509,491 Sell US$/Buy MYR 2020.01-2020.05 US$26,000/MYR108,330 Sell US$/Buy NT$ 2020.01-2020.02 US$170,000/NT$5,142,441 Sell US$/Buy SGD 2020.01-2020.02 US$8,600/SGD11,691 December 31, 2020 Sell RMB/Buy US$ 2021.01 RMB756,946/US$116,093 Sell HKD/Buy US$ 2021.01 HKD4,100/US$529 Sell NT$/Buy US$ 2021.01-2021.02 NT$2,667,230/US$95,000 Sell US$/Buy RMB 2021.01-2021.04 US$363,000/RMB2,385,500 Sell US$/Buy EUR 2021.01 US$1,607/EUR1,320 Sell US$/Buy JPY 2021.01-2021.04 US$100,076/JPY10,405,845 Sell US$/Buy KRW 2021.01 US$16,000/KRW17,575,300 Sell US$/Buy MYR 2021.01-2021.04 US$24,000/MYR98,737 Sell US$/Buy NT$ 2021.01-2021.02 US$27,470/NT$776,867 Sell US$/Buy SGD 2021.01-2021.04 US$18,500/SGD24,868 As of December 31, 2020, outstanding target redemption forward contracts not accounted for hedge accounting were as follows: Notional Amount Currency Maturity Period (In Thousands) Sell EUR/Buy US$ 2022.04-2022.06 EUR23,279/US$27,475 The target redeemable forward contracts held by subsidiaries are settled weekly. If the market exchange rate is lower than the execution rate at the time of settlement, the contract will be settled on the nominal amount, whereas if the market exchange rate is higher than the execution rate, th e

Financial Assets at Fair Value

Financial Assets at Fair Value Through Other Comprehensive Income (FVTOCI)	12 Months Ended
	Dec. 31, 2020
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Financial Assets at Fair Value Through Other Comprehensive Income (FVTOCI)	8. FINANCIAL ASSETS AT FAIR VALUE THROUGH OTHER COMPREHENSIVE INCOME (FVTOCI) December 31 2019 2020 NT$ NT$ US$ (Note 4) Investments in equity instruments at FVTOCI $ 755,903 $ 728,398 $ 25,940 Investments in debt instruments at FVTOCI 1,014,872 1,012,736 36,066 $ 1,770,775 $ 1,741,134 $ 62,006 a. Investments in equity instruments at FVTOCI December 31 2019 2020 NT$ NT$ US$ (Note 4) Unquoted ordinary shares $ 565,028 $ 567,377 $ 20,206 Unquoted preferred shares 158,718 151,329 5,389 Limited partnership 32,157 9,692 345 $ 755,903 $ 728,398 $ 25,940 b. Investments in debt instruments at FVTOCI December 31 2019 2020 NT$ NT$ US$ (Note 4) Unsecured subordinate corporate bonds $ 1,014,872 $ 1,012,736 $ 36,066 The Group purchased 1,000 units of perpetual unsecured subordinate corporate bonds in the amount of NT$1,000,000 thousand. The corporate bonds are in denomination of NT$1,000 thousand (US$36 thousand) with annual interest rate at 3.5% as well as effective interest rate at 3.2% both as of December 31, 2019 and 2020.

Credit Risk Management for Inve

Credit Risk Management for Investments in Debt Instruments	12 Months Ended
	Dec. 31, 2020
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Credit Risk Management for Investments in Debt Instruments	9. CREDIT RISK MANAGEMENT FOR INVESTMENTS IN DEBT INSTRUMENTS The Group’s investment in unsecured subordinate corporate bonds is rated the equivalent of investment grade or higher and has low credit risk for impairment assessment. There was no significant increase in credit risk of such debt instrument since initial recognition leading to changes in interest rates and terms, and there was also no significant change in bond issuer’s operation affecting the ability performing debt obligation. Therefore, no expected credit losses existed. The Group reviews changes in bond yields and other public information periodically and makes an assessment whether there has been a significant increase in lifetime Expected Credit Loss (“ECL”) since initial recognition.

Trade Receivables, Net

Trade Receivables, Net	12 Months Ended
	Dec. 31, 2020
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Trade Receivables, Net	10. TRADE RECEIVABLES, NET December 31 2019 2020 NT$ NT$ US$ (Note 4) At amortized cost Gross carrying amount $ 77,055,280 $ 91,304,934 $ 3,251,600 Less: Allowance for impairment loss 136,497 97,358 3,467 76,918,783 91,207,576 3,248,133 At FVTOCI 2,029,690 626,413 22,308 $ 78,948,473 $ 91,833,989 $ 3,270,441 a. Trade receivables 1) At amortized cost The Group’s average credit terms granted to the customers were 30 to 90 days. The Group evaluates the risk and probability of credit loss of trade receivables by reference to the Group’s past experiences, financial condition of each customer, impact of COVID-19, as well as competitive advantage and future development of the industry in which the customer operates. The Group then reviews the recoverable amount of each individual trade receivable at each balance sheet date to ensure that adequate allowance is made for possible irrecoverable amounts. In this regard, management believes the Group’s credit risk was significantly reduced. The Group measures the loss allowance for trade receivables at an amount equal to lifetime ECLs. The expected credit losses on trade receivables are estimated using a provision matrix by reference to past default experience of the debtor and an analysis of the debtor’s current financial position, adjusted for general economic conditions of the industry in which the debtors operate and an assessment of both the current as well as the forecast direction of economic conditions at each balance sheet date. As the Group’s historical credit loss experience shows significantly different loss patterns for different customer segments, the provision matrix for expected credit loss allowance based on trade receivables due status is further distinguished according to the Group’s different customer base. The Group writes off a trade receivable when there is information indicating that the debtor is in severe financial difficulty and there is no realistic prospect of recovery. For trade receivables that have been written off, the Group continues to engage in enforcement activity to attempt to recover the receivables due. Where recoveries are made, these are recognized in profit or loss. The following table details the loss allowance of trade receivables based on the Group’s provision matrix. December 31, 2019 Not Past Due Overdue 1 to 30 days Overdue 31 to 90 Days Overdue Over 91 Days Individually Impaired Total NT$ NT$ NT$ NT$ NT$ NT$ Expected credit loss rate 0% 0%-10% 0%-70% 1%-100% 50%-100% Gross carrying amount $ 70,042,018 $ 6,111,309 $ 695,384 $ 153,458 $ 53,111 $ 77,055,280 Loss allowance (Lifetime ECLs) (12,379 ) (841 ) (26,587 ) (53,629 ) (43,061 ) (136,497 ) $ 70,029,639 $ 6,110,468 $ 668,797 $ 99,829 $ 10,050 $ 76,918,783 December 31, 2020 Not Past Due Overdue 1 to 30 days Overdue 31 to 90 Days Overdue Over 91 Days Individually Impaired Total NT$ NT$ NT$ NT$ NT$ NT$ Expected credit loss rate 0% 0%-10% 0%-70% 1%-100% 50%-100% Gross carrying amount $ 86,820,792 $ 3,823,249 $ 557,487 $ 92,873 $ 10,533 $ 91,304,934 Loss allowance (Lifetime ECLs) (18,911 ) (2,053 ) (20,629 ) (45,232 ) (10,533 ) (97,358 ) $ 86,801,881 $ 3,821,196 $ 536,858 $ 47,641 $ - $ 91,207,576 Not Past Due Overdue 1 to 30 days Overdue 31 to 90 Days Overdue Over 91 Days Individually Impaired Total US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) Expected credit loss rate 0% 0%-10% 0%-70% 1%-100% 50%-100% Gross carrying amount $ 3,091,908 $ 136,156 $ 19,854 $ 3,307 $ 375 $ 3,251,600 Loss allowance (Lifetime ECLs) (673 ) (73 ) (735 ) (1,611 ) (375 ) (3,467 ) $ 3,091,235 $ 136,083 $ 19,119 $ 1,696 $ - $ 3,248,133 The movements of the loss allowance of trade receivables for the years ended were as follows: December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Balance at January 1 $ 64,901 $ 155,389 $ 136,497 $ 4,861 Net remeasurement of loss allowance 150,128 (38,277 ) (55,742 ) (1,985 ) Reclassification - (5,877 ) (6,970 ) (248 ) Acquisition through business combinations 3,482 25,553 32,460 1,156 Amounts written off (60,109 ) - (3,944 ) (141 ) Effects of foreign currency exchange differences (3,013 ) (291 ) (4,943 ) (176 ) Balance at December 31 $ 155,389 $ 136,497 $ 97,358 $ 3,467 2) At FVTOCI For the trade receivables due from certain customers, the Group decides whether or not to factor these trade receivables to banks without recourse based on the Group’s demand of working capital. These trade receivables are classified as at FVTOCI because they are held within a business model whose objective is achieved by both the collecting of contractual cash flows and the selling of financial assets. The following table details the loss allowance of trade receivables at FVTOCI based on the Group’s provision matrix. December 31, 2019 Not Past Due Overdue 1 to 30 days Overdue 31 to 90 Days Overdue Over 91 Days Individually Impaired Total NT$ NT$ NT$ NT$ NT$ NT$ Expected credit loss rate 0% - 0% 1% - Gross carrying amount $ 2,029,324 $ - $ 207 $ 160 $ - $ 2,029,691 Loss allowance (Lifetime ECLs) - - - (1 ) - (1 ) $ 2,029,324 $ - $ 207 $ 159 $ - $ 2,029,690 December 31, 2020 Not Past Due Overdue 1 to 30 days Overdue 31 to 90 Days Overdue Over 91 Days Individually Impaired Total NT$ NT$ NT$ NT$ NT$ NT$ Expected credit loss rate 0% 0% 0% - - Gross carrying amount $ 613,968 $ 9,874 $ 2,571 $ - $ - $ 626,413 Loss allowance (Lifetime ECLs) - - - - - - $ 613,968 $ 9,874 $ 2,571 $ - $ - $ 626,413 Not Past Due Overdue 1 to 30 days Overdue 31 to 90 Days Overdue Over 91 Days Individually Impaired Total US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) Expected credit loss rate 0% 0% 0% - - Gross carrying amount $ 21,864 $ 352 $ 92 $ - $ - $ 22,308 Loss allowance (Lifetime ECLs) - - - - - - $ 21,864 $ 352 $ 92 $ - $ - $ 22,308 3) At FVTPL Some of the Group’s subsidiaries sell all of their trade receivables to banks without recourse. The sale will result in the derecognition of these trade receivables because the Group’s subsidiaries will transfer substantially all risks and rewards to banks. These trade receivables are measured at FVTPL because the objective of the subsidiary’ business model is neither the collecting of contractual cash flows nor the collecting of contractual cash flows and the selling of financial assets. As of December 31, 2020, the trade receivables at FVTPL were all factored to banks without recourse. b. Transfers of financial assets The followings were the Group’s outstanding trade receivables transferred but not yet due were as follows: Counterparties Receivables Factoring Proceeds Reclassified to Other Receivables Advances Received- Unused Advances Received- Used Interest Rates on Advances Received December 31, 2019 First Commercial Bank NT$ 7,567 NT$ - NT$ - NT$ 7,567 2.2% December 31, 2020 BNP Paribas EUR 16,691 EUR 15,315 EUR 14,481 EUR 1,376 0.80% HSBC EUR 6,773 EUR 6,456 EUR 5,779 EUR 317 1.45% Citibank Taiwan Ltd. US$ 94,471 US$ - US$ - US$ 94,471 0.84%-0.95 Standard Chartered Bank US$ 53,800 US$ - US$ - US$ 53,800 0.91% First Commercial Bank NT$ 6,879 NT$ - NT$ - NT$ 6,879 1.95% Pursuant to the factoring agreements, losses from commercial disputes (such as sales returns and discounts) are borne by the Group, while losses from credit risk are borne by banks. As of December 31, 2020, the Group issued promissory notes with aggregate amounts of US$2,000 thousand to Citibank Taiwan Ltd. to compensate losses from commercial disputes. In 2020, the Group did not have material commercial dispute in the past and expected to have no material commercial dispute in the foreseeable future.

Inventories

Inventories	12 Months Ended
	Dec. 31, 2020
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Inventories	11. INVENTORIES December 31 2019 2020 NT$ NT$ US$ (Note 4) Finished goods $ 7,174,716 $ 8,788,460 $ 312,979 Work in process 2,952,182 6,816,602 242,757 Raw materials 20,996,346 29,428,008 1,048,006 Supplies 2,229,576 2,691,779 95,861 Raw materials and supplies in transit 530,930 791,610 28,191 $ 33,883,750 $ 48,516,459 $ 1,727,794 The cost of inventories recognized as operating costs for the years ended December 31, 2018, 2019 and 2020 were NT$309,020,850 thousand, NT$347,877,603 thousand and NT$398,068,260 thousand (US$14,176,220 thousand), respectively, which included write-downs of inventories at NT$980,927 thousand, NT$452,134 thousand and NT$1,493,793 thousand (US$53,198 thousand), respectively.

Inventories Related to Real Est

Inventories Related to Real Estate Business	12 Months Ended
	Dec. 31, 2020
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Inventories Related to Real Estate Business	12. INVENTORIES RELATED TO REAL ESTATE BUSINESS December 31 2019 2020 NT$ NT$ US$ (Note 4) Land and buildings held for sale $ 9,983 $ 625,791 $ 22,286 Construction in progress 9,619,217 11,058,328 393,815 Land held for construction 1,787,526 1,787,526 63,659 $ 11,416,726 $ 13,471,645 $ 479,760 Construction in progress is mainly located on Hutai Road in Shanghai, China and Lidu Road in Kun Shan, China. The capitalized borrowing costs for the years ended December 31, 2018, 2019 and 2020 are disclosed in Note 25. As of December 31, 2019 and 2020, inventories related to real estate business of NT$11,416,726 thousand and NT$13,471,645 thousand (US$479,759 thousand), respectively, are expected to be recovered longer than twelve months. Refer to Note 36 for the carrying amount of inventories related to real estate business that had been pledged by the Group to secure bank borrowings.

Other Financial Assets

Other Financial Assets	12 Months Ended
	Dec. 31, 2020
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Other Financial Assets	13. OTHER FINANCIAL ASSETS December 31 2019 2020 NT$ NT$ US$ (Note 4) Guarantee deposits $ 661,667 $ 516,505 $ 18,394 Pledged time deposits (Note 36) 620,817 367,550 13,089 Time deposits with original maturity of over three months 25,885 35,988 1,282 December 31 2019 2020 NT$ NT$ US$ (Note 4) Others (Note 36) $ 16,958 $ 161,957 $ 5,768 1,325,327 1,082,000 38,533 Current 765,834 551,655 19,646 Non-current $ 559,493 $ 530,345 $ 18,887

Investments Accounted for Using

Investments Accounted for Using the Equity Method	12 Months Ended
	Dec. 31, 2020
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Investments Accounted for Using the Equity Method	14. INVESTMENTS ACCOUNTED FOR USING THE EQUITY METHOD December 31 2019 2020 NT$ NT$ US$ (Note 4) Investments in associates $ 11,805,505 $ 12,335,239 $ 439,289 Investments in joint ventures 279,702 471,434 16,789 $ 12,085,207 $ 12,806,673 $ 456,078 a. Investments in associates 1) Investments in associates accounted for using the equity method that was not individually material consisted of the following: Carrying Amount as of December 31 Operating 2019 2020 Name of Associate Main Business Location NT$ NT$ US$ (Note 4) Yann Yuan Investment Co., Ltd. (“Yann Yuan”) Engaged in investing activities R.O.C. $ 3,934,190 $ 6,670,035 $ 237,537 ChipMOS Technologies Inc. (“ChipMOS”) Engaged in the packaging and testing of semiconductors R.O.C. 4,370,075 2,406,843 85,714 M-Universe Investments Pte. Ltd. (“MU”) Investment company Singapore 1,814,699 1,848,588 65,833 Hung Ching Development & Construction Co. (“HC”) Engaged in the development, construction and leasing of real estate properties R.O.C. 1,380,162 1,352,760 48,175 Hung Ching Kwan Co. (“HCK”) Engaged in the leasing of real estate properties R.O.C. 283,105 270,087 9,618 Deca Technologies Inc. (”DECA” ） Holding company and the group engaged in manufacturing, development and marketing of wafer level packaging and interconnect technology British Cayman 323,423 87,075 3,101 12,105,654 12,635,388 449,978 Less: Deferred gain on transfer of land 300,149 300,149 10,689 $ 11,805,505 $ 12,335,239 $ 439,289 2) At each balance sheet date, the percentages of ownership held by the Group’s subsidiary were as follows: December 31 2019 2020 Yann Yuan 32.21 % 32.21 % ChipMOS 20.48 % 10.85 % MU 42.23 % 42.23 % HC 26.22 % 26.22 % HCK 27.31 % 27.31 % DECA 22.02 % 17.85 % 3) The Group evaluated the recoverable amount of its investment in DECA’s preferred shares using the fair value less costs of disposal in 2019. The recoverable amount was lower than the carrying amount and, therefore, the Group recognized an impairment loss of NT$400,201 thousand under the line item of other gains and losses (Note 25). The fair value was the estimated transaction price of DECA’s preferred shares, of which the fair value hierarchy was Level 3. In the first quarter of 2020, the Group’s percentage of ownership in DECA decreased to 17.85% due to the partial disposal of ownership in DECA and the issuance of preferred shares by DECA, and a gain on disposal of NT$17,180 thousand (US$612 thousand) was recognized under the line item of other gains and losses (Note 25). The Group considered it still has significant influence over DECA since the Group continuously involves in making significant decisions by participating in DECA’s board meeting. 4) In June 2020, the Group’s subsidiary, SPIL, disposed 70,000 thousand ordinary shares of ChipMOS at NT$32 per share, which resulted the Group’s percentage of ownership in ChipMOS decreased to 10.85% and a gain on disposal of NT$74,117 thousand (US$2,639 thousand) was recognized under the line item of other gains and losses (Note 25). The Group considered it still has significant influence over ChipMOS since the Group continuously involves in making significant decisions by participating in ChipMOS’s board meeting. 5) Fair values (Level 1) of investments in associates with available published price quotation are summarized as follows: December 31 2019 2020 NT$ NT$ US$ (Note 4) ChipMOS $ 5,100,181 $ 2,710,572 $ 96,530 HC $ 1,551,033 $ 1,317,692 $ 46,926 6) Aggregate information of associates that are not individually material For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) The Group’s share of: Net profit $ 147,535 $ 321,413 $ 545,833 $ 19,438 Other comprehensive income (loss) (613,471 ) 1,401,453 2,784,094 99,149 Total comprehensive income (loss) $ (465,936 ) $ 1,722,866 $ 3,329,927 $ 118,587 b. Investments in joint ventures 1) Investments in joint ventures that were not individually material and accounted for using the equity method consisted of the following: Carrying Amount as of December 31 2019 2020 Operating NT$ NT$ US$ (Note 4) Name of Joint Venture Main Business Location SUMA-USI Electronics Co., Ltd. (“SUMA-USI”) Engaged in the design and production of electronic products China $ 279,702 $ 471,434 $ 16,789 2) At each balance sheet date, the percentages of ownership held by the Group’s subsidiary were as follows: December 31 2019 2020 SUMA-USI 49.00 % 49.00 % 3) In March 2019, UGKS entered into a joint venture agreement with Cancon Information Industry Co., Ltd. to establish SUMA-USI and obtained 49.00% ownership of SUMA-USI. As of December 31, 2020, the Group has invested RMB107,800 thousand (equivalent to NT$469,307 thousand (US$16,713 thousand)) in SUMA-USI. Based on the joint venture agreement, both investors jointly lead the relevant operation activities of SUMA-USI, which resulted the Group’s investment in SUMA-USI was accounted for using the equity method. 4) As disclosed in Note 29, the Group obtained control over ASEEE in April 2019. 5) Aggregate information of joint ventures that were not individually material For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) The Group’s share of: Net profit (loss) $ (306,156 ) $ (139,137 ) $ 1,780 $ 63 Other comprehensive income (loss) - (3,169 ) 3,881 138 Total comprehensive income (loss) $ (306,156 ) $ (142,306 ) $ 5,661 $ 201

Property, Plant and Equipment

Property, Plant and Equipment	12 Months Ended
	Dec. 31, 2020
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Property, Plant and Equipment	15. PROPERTY, PLANT AND EQUIPMENT The carrying amounts of each class of property, plant and equipment were as follows: December 31 2019 2020 NT$ NT$ US$ (Note 4) Land $ 10,333,822 $ 10,336,568 $ 368,112 Buildings and improvements 85,409,580 82,273,186 2,929,957 December 31 2019 2020 NT$ NT$ US$ (Note 4) Machinery and equipment $ 112,996,670 $ 122,063,883 $ 4,347,004 Other equipment 6,715,694 4,680,222 166,674 Construction in progress and machinery in transit 16,637,561 13,853,465 493,357 $ 232,093,327 $ 233,207,324 $ 8,305,104 For the year ended December 31, 2018 Land Buildings and Improvements Machinery and Equipment Other Equipment Construction in Progress and Machinery in Transit Total NT$ NT$ NT$ NT$ NT$ NT$ Cost Balance at January 1, 2018 $ 3,258,518 $ 100,187,928 $ 253,198,003 $ 7,812,080 $ 5,863,713 $ 370,320,242 Additions - 144,898 192,673 84,860 38,669,807 39,092,238 Disposals - (677,206 ) (26,493,282 ) (2,251,060 ) (34,902 ) (29,456,450 ) Reclassification - 5,388,709 32,060,513 2,148,211 (39,612,324 ) (14,891 ) Acquisition through business combinations (Note 29) 6,880,400 37,127,957 95,810,062 11,122,171 5,781,189 156,721,779 Effect of foreign currency exchange differences 27,051 (464,275 ) (929,579 ) (78,095 ) 244,069 (1,200,829 ) Balance at December 31, 2018 $ 10,165,969 $ 141,708,011 $ 353,838,390 $ 18,838,167 $ 10,911,552 $ 535,462,089 Accumulated depreciation and impairment Balance at January 1, 2018 $ - $ 41,915,064 $ 187,012,805 $ 6,223,967 $ - $ 235,151,836 Depreciation expenses - 6,325,948 31,751,251 1,816,587 - 39,893,786 Impairment losses recognized - 29,531 97,680 5,860 - 133,071 Disposals - (491,033 ) (25,704,778 ) (2,070,302 ) - (28,266,113 ) Reclassification - (265 ) - - - (265 ) Acquisition through business combinations (Note 29) - 15,097,920 53,210,063 6,428,174 - 74,736,157 Effect of foreign currency exchange differences - (133,091 ) (616,601 ) (29,279 ) - (778,971 ) Balance at December 31, 2018 $ - $ 62,744,074 $ 245,750,420 $ 12,375,007 $ - $ 320,869,501 For the year ended December 31, 2019 Land Buildings and Improvements Machinery and Equipment Other Equipment Construction in Progress and Machinery in Transit Total NT$ NT$ NT$ NT$ NT$ NT$ Cost Balance at January 1, 2019 $ 10,165,969 $ 141,708,011 $ 353,838,390 $ 18,380,122 $ 10,911,552 $ 535,004,044 Additions - 806,844 413,008 76,671 61,777,364 63,073,887 Disposals - (983,690 ) (19,139,634 ) (2,507,440 ) - (22,630,764 ) Reclassification - 13,601,469 41,302,651 3,062,838 (57,221,627 ) 745,331 Acquisitions through business combinations (Note 29) 189,111 1,044,383 5,507,315 43,611 250,455 7,034,875 Effect of foreign currency exchange differences (21,258 ) (2,204,057 ) (5,176,282 ) (300,686 ) 919,817 (6,782,466 ) Balance at December 31, 2019 $ 10,333,822 $ 153,972,960 $ 376,745,448 $ 18,755,116 $ 16,637,561 $ 576,444,907 Accumulated depreciation and impairment Balance at January 1, 2019 $ - $ 62,744,074 $ 245,750,420 $ 12,194,041 $ - $ 320,688,535 Depreciation expense - 6,989,392 35,747,308 2,503,967 - 45,240,667 Impairment losses recognized - 78,562 102,056 20,388 - 201,006 Disposals - (881,149 ) (18,640,266 ) (2,503,438 ) - (22,024,853 ) Reclassification - 210,558 83,777 (103 ) - 294,232 Land Buildings and Improvements Machinery and Equipment Other Equipment Construction in Progress and Machinery in Transit Total NT$ NT$ NT$ NT$ NT$ NT$ Acquisitions through business combinations (Note 29) - 445,682 4,000,338 19,028 - 4,465,048 Effect of foreign currency exchange differences - (1,023,739 ) (3,294,855 ) (194,461 ) - (4,513,055 ) Balance at December 31, 2019 $ - $ 68,563,380 $ 263,748,778 $ 12,039,422 $ - $ 344,351,580 For the year ended December 31, 2020 Land Buildings and Improvements Machinery and Equipment Other Equipment Construction in Progress and Machinery in Transit Total NT$ NT$ NT$ NT$ NT$ NT$ Cost Balance at January 1, 2020 $ 10,333,822 $ 153,972,960 $ 376,745,448 $ 18,755,116 $ 16,637,561 $ 576,444,907 Additions - 86,409 695,561 47,137 58,195,094 59,024,201 Disposals - (365,758 ) (12,818,849 ) (2,419,423 ) (126,605 ) (15,730,635 ) Disposal of subsidiaries (Note 30) - (3,665,811 ) (3,223,448 ) (445,506 ) (792,543 ) (8,127,308 ) Reclassification - 7,367,875 52,980,977 222,066 (60,032,844 ) 538,074 Acquisitions through business combinations (Note 29) 46,388 1,142,690 3,972,397 702,500 53,828 5,917,803 Effect of foreign currency exchange differences (43,642 ) (266,536 ) (2,459,521 ) (11,008 ) (81,026 ) (2,861,733 ) Balance at December 31, 2020 $ 10,336,568 $ 158,271,829 $ 415,892,565 $ 16,850,882 $ 13,853,465 $ 615,205,309 Accumulated depreciation and impairment Balance at January 1, 2020 $ - $ 68,563,380 $ 263,748,778 $ 12,039,422 $ - $ 344,351,580 Depreciation expense - 7,401,223 36,373,712 2,241,613 - 46,016,548 Impairment losses recognized - - 981,535 10,738 - 992,273 Disposals - (300,832 ) (8,306,990 ) (2,398,756 ) - (11,006,578 ) Disposal of subsidiaries (Note 30) - (153,002 ) (345,834 ) (82,059 ) - (580,895 ) Reclassification - 3,462 497,230 (188,844 ) - 311,848 Acquisitions through business combinations (Note 29) - 548,190 3,049,895 588,935 - 4,187,020 Effect of foreign currency exchange differences - (63,778 ) (2,169,644 ) (40,389 ) - (2,273,811 ) Balance at December 31, 2020 $ - $ 75,998,643 $ 293,828,682 $ 12,170,660 $ - $ 381,997,985 Land Buildings and Improvements Machinery and Equipment Other Equipment Construction in Progress and Machinery in Transit Total US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) Cost Balance at January 1, 2020 $ 368,014 $ 5,483,368 $ 13,416,861 $ 667,917 $ 592,506 $ 20,528,666 Additions - 3,077 24,771 1,678 2,072,475 2,102,001 Disposals - (13,026 ) (456,512 ) (86,162 ) (4,509 ) (560,209 ) Disposal of subsidiaries (Note 30) - (130,549 ) (114,795 ) (15,866 ) (28,224 ) (289,434 ) Reclassification - 262,389 1,886,787 7,908 (2,137,922 ) 19,162 Acquisitions through business combinations (Note 29) 1,652 40,694 141,467 25,018 1,917 210,748 Effect of foreign currency exchange differences (1,554 ) (9,492 ) (87,590 ) (391 ) (2,886 ) (101,913 ) Balance at December 31, 2020 $ 368,112 $ 5,636,461 $ 14,810,989 $ 600,102 $ 493,357 $ 21,909,021 Accumulated depreciation and impairment Balance at January 1, 2020 $ - $ 2,441,716 $ 9,392,763 $ 428,754 $ - $ 12,263,233 Depreciation expense - 263,576 1,295,360 79,830 - 1,638,766 Impairment losses recognized - - 34,955 382 - 35,337 Disposals - (10,713 ) (295,833 ) (85,426 ) - (391,972 ) Disposal of subsidiaries (Note 30) - (5,449 ) (12,316 ) (2,922 ) - (20,687 ) Reclassification - 123 17,708 (6,725 ) - 11,106 Acquisitions through business combinations (Note 29) - 19,522 108,615 20,973 - 149,110 Effect of foreign currency exchange differences - (2,271 ) (77,267 ) (1,438 ) - (80,976 ) Balance at December 31, 2020 $ - $ 2,706,504 $ 10,463,985 $ 433,428 $ - $ 13,603,917 Based on the future operation plans and the capacity evaluation, the Group assessed that a portion of plant and equipment in the packaging segment and the testing segment were not qualified for the production needs and, therefore, recognized an impairment loss of NT$133,071 thousand, NT$201,006 thousand and NT$992,273 thousand (US$35,337 thousand) under the line item of other operating income and expenses (Note 25) for the years ended December 31, 2018, 2019 and 2020, respectively. The recoverable amounts of a portion of the impaired plant and equipment were determined by their fair value less cost of disposal, of which the fair value was based on the recent quoted prices of assets with similar age and obsolescence provided by vendors in secondary market or the disposal price, and both of which represented Level 3 inputs because the secondary market was not active and the disposal price was negotiated with counter-parties. The recoverable amounts of the remaining impaired plant and equipment were determined by their value in use and the Group expects only short-term or no economic benefits would be generated by these assets and the discount effect of was immaterial. Each class of property, plant and equipment was depreciated on a straight-line basis over the following useful lives: Buildings and improvements Main plant buildings 10-55 years Cleanrooms 10-20 years Others 3-20 years Machinery and equipment 2-10 years Other equipment 2-20 years The capitalized borrowing costs for the years ended December 31, 2018, 2019 and 2020 are disclosed in Note 25.

Lease Arrangements

Lease Arrangements	12 Months Ended
	Dec. 31, 2020
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Lease Arrangements	16. LEASE ARRANGEMENTS a. Right-of-use assets December 31 2019 2020 NT$ NT$ US$ (Note 4) Carrying amounts Land $ 7,036,887 $ 5,840,779 $ 208,005 Buildings and improvements 2,121,797 2,548,838 90,771 Machinery and equipment 588,443 181,065 6,448 Other equipment 45,094 49,930 1,778 $ 9,792,221 $ 8,620,612 $ 307,002 December 31 2019 2020 NT$ NT$ US$ (Note 4) Additions to right-of-use assets $ 824,268 $ 702,996 $ 25,035 Depreciation charge for right-of-use assets Land $ 215,301 $ 214,682 $ 7,645 Buildings and improvements 307,708 370,458 13,193 December 31 2019 2020 NT$ NT$ US$ (Note 4) Machinery and equipment $ 507,443 $ 335,039 $ 11,932 Other equipment 25,006 26,701 951 $ 1,055,458 $ 946,880 $ 33,721 The amounts disclosed above with respect to the right-of-use assets did not include the right-of-use assets that meet the definition of investment properties. b. Lease liabilities December 31 2019 2020 NT$ NT$ US$ (Note 4) Carrying amounts Current $ 632,802 $ 774,444 $ 27,580 Non-current $ 5,176,123 $ 5,101,386 $ 181,673 The Group’s lease liabilities were mainly from land and buildings and improvements. The range of discount rates for lease liabilities was as follows: December 31 2019 2020 Land (%) 0.54-4.90 0.54-8.00 Buildings and improvements (%) 0.30-8.62 0.54-8.84 c. Material lease-in activities and terms The Group leases land and buildings for the use of plants and offices with remaining lease terms of 1-54 years and 1-30 years, respectively. For the leasehold land located in the R.O.C., the Group has extension options at the expiry of the lease periods. However, the government has the right to adjust the lease payments on the basis of changes in announced land value prices and also has the right to terminate the lease contract under certain circumstances. The Group does not have bargain purchase options to acquire the leasehold land and buildings at the expiry of the lease periods. In addition, the Group is prohibited from subleasing or transferring all or any portion of the underlying assets without the lessor’s consent. d. Subleases In addition to the sublease transactions described in Note 17, the Group did not have other sublease transactions. e. Other lease information December 31 2019 2020 NT$ NT$ US$ (Note 4) Expenses relating to short-term leases $ 421,924 $ 682,142 $ 24,293 Expenses relating to low-value assets leases $ 4,473 $ 5,433 $ 193 Expenses relating to variable lease payments not included in the measurement of lease liabilities $ 53,403 $ 43,112 $ 1,535 Total cash outflow for leases $ (1,511,277 ) $ (1,854,456 ) $ (66,042 ) The Group elected to apply the recognition exemption for qualifying short-term leases and low-value asset leases and, thus, did not recognize right-of-use assets and lease liabilities for these leases.

Investment Properties

Investment Properties	12 Months Ended
	Dec. 31, 2020
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Investment Properties	17. INVESTMENT PROPERTIES For the year ended December 31, 2018 Land Buildings and Improvements Total NT$ NT$ NT$ Cost Balance at January 1, 2018 $ 35,965 $ 8,406,785 $ 8,442,750 Additions - 125,853 125,853 Reclassification - 14,891 14,891 Effects of foreign currency exchange differences - (137,739 ) (137,739 ) Balance at December 31, 2018 $ 35,965 $ 8,409,790 $ 8,445,755 Accumulated depreciation and impairment Balance at January 1, 2018 $ - $ 323,314 $ 323,314 Depreciation expenses - 392,667 392,667 Reclassification - 265 265 Effects of foreign currency exchange differences - (8,870 ) (8,870 ) Balance at December 31, 2018 $ - $ 707,376 $ 707,376 Carrying amount at December 31, 2018 $ 35,965 $ 7,702,414 $ 7,738,379 For the year ended December 31, 2019 Land Buildings and Improvements Right-of-use Assets Total NT$ NT$ NT$ NT$ Cost Balance at January 1, 2019 $ 35,965 $ 8,409,790 $ 6,891,947 $ 15,337,702 Additions - 2,532 - 2,532 Disposals - (1,843 ) - (1,843 ) Reclassification - (490,130 ) (21,069 ) (511,199 ) Effects of foreign currency exchange differences - (209,980 ) (303,086 ) (513,066 ) Balance at December 31, 2019 $ 35,965 $ 7,710,369 $ 6,567,792 $ 14,314,126 Accumulated depreciation and impairment Balance at January 1, 2019 $ - $ 707,376 $ 292,722 $ 1,000,098 Depreciation expenses - 377,536 216,574 594,110 Disposals - (1,240 ) - (1,240 ) Reclassification - (210,455 ) 543 (209,912 ) Effects of foreign currency exchange differences - 99,354 (22,355 ) 76,999 Balance at December 31, 2019 $ - $ 972,571 $ 487,484 $ 1,460,055 Carrying amount at December 31, 2019 $ 35,965 $ 6,737,798 $ 6,080,308 $ 12,854,071 For the year ended December 31, 2020 Land Buildings and Improvements Right-of-use Assets Total NT$ NT$ NT$ NT$ Cost Balance at January 1, 2020 $ 35,965 $ 7,710,369 $ 6,567,792 $ 14,314,126 Additions - 6,352 - 6,352 Disposals - (1,902 ) - (1,902 ) Reclassification - (3,884 ) 46,201 42,317 Effects of foreign currency exchange differences - 111,870 124,920 236,790 Balance at December 31, 2020 $ 35,965 $ 7,822,805 $ 6,738,913 $ 14,597,683 Land Buildings and Improvements Right-of-use Assets Total US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) Cost Balance at January 1, 2020 $ 1,281 $ 274,586 $ 233,896 $ 509,763 Additions - 226 - 226 Disposals - (68 ) - (68 ) Reclassification - (138 ) 1,645 1,507 Effects of foreign currency exchange differences - 3,984 4,449 8,433 Balance at December 31, 2020 $ 1,281 $ 278,590 $ 239,990 $ 519,861 Accumulated depreciation Balance at January 1, 2020 $ - $ 34,636 $ 17,360 $ 51,996 Depreciation expenses - 12,573 7,450 20,023 Disposals - (46 ) - (46 ) Reclassification - (53 ) 378 325 Effects of foreign currency exchange differences - 699 351 1,050 Balance at December 31, 2020 $ - $ 47,809 $ 25,539 $ 73,348 Carrying amount at December 31, 2020 $ 1,281 $ 230,781 $ 214,451 $ 446,513 Right-of-use assets included in investment properties were leasehold land located in Shanghai and were subleased under operating leases. The abovementioned investment properties were leased out for 1 to 15 years, with an option to extend for an additional lease term. The lease contracts contain market review clauses in the event that the lessees exercise their options to extend. The lessees do not have bargain purchase options to acquire the investment properties at the expiry of the lease term. In addition to fixed lease payments, some of the lease contracts also indicated that the lessees should make variable payments determined at a specific percentage of the excess of respective lessee’s monthly revenues over a specific amount. The maturity analysis of lease payments receivable under operating leases of investment properties was as follows: December 31 2019 2020 NT$ NT$ US$ (Note 4) Year 1 $ 921,649 $ 880,929 $ 31,372 Year 2 744,366 688,123 24,506 Year 3 623,326 471,966 16,808 Year 4 408,634 383,307 13,651 Year 5 320,611 335,706 11,955 Year 6 onwards 830,091 664,259 23,656 $ 3,848,677 $ 3,424,290 $ 121,948 The investment properties were depreciated on a straight-line basis over the following useful lives: Main buildings 10-40 years Right-of-use assets 15-50 years Because of the market conditions severely affected by COVID-19 in 2020, the Group agreed to provide unconditional rent reduction for some lease contracts. The rent concessions were accounted for as adjustments to related income over the remaining lease term. For the year ended December 31, 2020, total amount from the rent concessions was NT$54,139 thousand (US$1,928 thousand). The fair value of the investment properties was measured using the market approach and the income approach based on level 3 inputs by independent professional appraisers. The significant unobservable inputs were discount rates. The fair value of the investment properties was as follows: December 31 2019 2020 NT$ NT$ US$ (Note 4) Fair value $ 19,586,287 $ 19,799,714 $ 705,118 Refer to Note 36 for the carrying amount of the investment properties that had been pledged by the Group to secure borrowings.

Goodwill

Goodwill	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Goodwill	18. GOODWILL Cost Accumulated impairment Carrying amount NT$ NT$ NT$ For the year ended December 31, 2018 Balance at January 1, 2018 $ 12,348,607 $ 2,414,113 $ 9,934,494 Cost Accumulated impairment Carrying amount NT$ NT$ NT$ Acquisition through business combinations (Note 29) 39,990,231 - 39,990,231 Effect of foreign currency exchange differences 49,721 - 49,721 Balance at December 31, 2018 $ 52,388,559 $ 2,414,113 $ 49,974,446 For the year ended December 31, 2019 Balance at January 1, 2019 $ 52,388,559 $ 2,414,113 $ 49,974,446 Acquisition through business combinations (Note 29) 264,977 - 264,977 Effect of foreign currency exchange differences (40,987 ) - (40,987 ) Balance at December 31, 2019 $ 52,612,549 $ 2,414,113 $ 50,198,436 For the year ended December 31, 2020 Balance at January 1, 2020 $ 52,612,549 $ 2,414,113 $ 50,198,436 Acquisition through business combinations (Note 29) 4,625,269 - 4,625,269 Effect of foreign currency exchange differences (46,266 ) - (46,266 ) Balance at December 31, 2020 $ 57,191,552 $ 2,414,113 $ 54,777,439 Cost Accumulated Impairment Carrying Amount US$ (Note 4) US$ (Note 4) US$ (Note 4) For the year ended December 31, 2020 Balance at January 1, 2020 $ 1,873,666 $ 85,973 $ 1,787,693 Acquisition through business combinations (Note 29) 164,718 - 164,718 Effect of foreign currency exchange differences (1,647 ) - (1,647 ) Balance at December 31, 2020 $ 2,036,737 $ 85,973 $ 1,950,764 a. Allocating goodwill to cash-generating units The Group did not monitor goodwill for internal management purpose but for financial reporting purpose and, therefore, the goodwill was allocated to the following cash-generating units for evaluation of impairment: packaging segment, testing segment, EMS segment and other segment. The carrying amounts of goodwill allocated to cash-generating units were as follows: December 31 2019 2020 Cash-generating units NT$ NT$ US$ (Note 4) Packaging segment $ 35,717,828 $ 35,703,625 $ 1,271,496 Testing segment 13,421,321 13,365,068 475,964 EMS segment (Note 29) 903,346 5,560,645 198,029 Others 155,941 148,101 5,275 $ 50,198,436 $ 54,777,439 $ 1,950,764 b. Impairment assessment At the end of each year, the Group performs evaluation of goodwill for impairment by reviewing the recoverable amounts based on value in use which incorporates cash flow projections estimated by management covering a five-year period. The cash flows beyond that five-year period are extrapolated using a steady per annum growth rate. In assessing value in use, the estimated future cash flows are discounted to their present value using annual pre-tax discount rates which were 9.74%-10.22%, 9.59%-14.99% and 10.39%-14.71% as of December 31, 2018, 2019 and 2020, respectively. For the years ended December 31, 2018, 2019 and 2020, no impairment loss was recognized. The key assumption used in calculating each segment’s value in use also included the growth rates for operating revenues, which were based on the forecast for the Group and the industry as well as the Group’s historical performance. Management believes that any reasonably possible change in the key assumptions on which the recoverable amount was based would not cause the carrying amount of the cash-generating unit to exceed its recoverable amount.

Other Intangible Assets

Other Intangible Assets	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Other Intangible Assets	19. OTHER INTANGIBLE ASSETS The carrying amounts of each class of other intangible assets were as follows: December 31 2019 2020 NT$ NT$ US$ (Note 4) Customer relationships $ 9,333,333 $ 8,334,203 $ 296,802 Computer software 1,929,539 2,678,867 95,401 Patents and acquired specific technology 17,718,523 15,720,213 559,837 Others 42,997 75,385 2,685 $ 29,024,392 $ 26,808,668 $ 954,725 For the year ended December 31, 2018 Customer Relationships Computer Software Patents and Acquired Specific Technology Others Total NT$ NT$ NT$ NT$ NT$ Cost Balance at January 1, 2018 $ 915,636 $ 3,686,452 $ 389,486 $ 198,754 $ 5,190,328 Additions - 528,883 - 8,776 537,659 Disposals - (95,358 ) (231 ) (4,000 ) (99,589 ) Acquisition through business combinations (Note 29) 11,000,000 274,868 20,200,000 32,800 31,507,668 Effect of foreign currency exchange differences - 6,200 (899 ) (332 ) 4,969 Balance at December 31, 2018 $ 11,915,636 $ 4,401,045 $ 20,588,356 $ 235,998 $ 37,141,035 Accumulated amortization Balance at January 1, 2018 $ 801,860 $ 2,822,121 $ 70,084 $ 89,398 $ 3,783,463 Amortization expense 746,979 373,536 1,263,309 18,626 2,402,450 Disposals - (95,202 ) (231 ) (4,000 ) (99,433 ) Acquisition through business combinations (Note 29) - 137,799 - 15,483 153,282 Effect of foreign currency exchange differences - 3,109 (475 ) 939 3,573 Balance at December 31, 2018 $ 1,548,839 $ 3,241,363 $ 1,332,687 $ 120,446 $ 6,243,335 For the year ended December 31, 2019 Customer Relationships Computer Software Patents and Acquired Specific Technology Others Total NT$ NT$ NT$ NT$ NT$ Cost Balance at January 1, 2019 $ 11,915,636 $ 4,401,045 $ 20,588,356 $ 83,657 $ 36,988,694 Additions - 1,358,533 - (7,625 ) 1,350,908 Disposals or derecognization (915,635 ) (1,123,446 ) - (6,315 ) (2,045,396 ) Acquisition through business combinations (Note 29) - 19,944 732,604 - 752,548 Customer Relationships Computer Software Patents and Acquired Specific Technology Others Total NT$ NT$ NT$ NT$ NT$ Effect of foreign currency exchange differences $ - $ (49,198 ) $ (2,264 ) $ (1,417 ) $ (52,879 ) Balance at December 31, 2019 $ 11,000,001 $ 4,606,878 $ 21,318,696 $ 68,300 $ 36,993,875 Accumulated amortization Balance at January 1, 2019 $ 1,548,839 $ 3,241,363 $ 1,332,687 $ 27,772 $ 6,150,661 Amortization expense 1,033,464 583,300 1,955,703 4,139 3,576,606 Disposals or derecognization (915,635 ) (1,116,512 ) - (6,315 ) (2,038,462 ) Acquisition through business combinations (Note 29) - 7,765 313,422 - 321,187 Effect of foreign currency exchange differences - (38,577 ) (1,639 ) (293 ) (40,509 ) Balance at December 31, 2019 $ 1,666,668 $ 2,677,339 $ 3,600,173 $ 25,303 $ 7,969,483 For the year ended December 31, 2020 Customer Relationships Computer Software Patents and Acquired Specific Technology Others Total NT$ NT$ NT$ NT$ NT$ Cost Balance at January 1, 2020 $ 11,000,001 $ 4,606,878 $ 21,318,696 $ 68,300 $ 36,993,875 Additions - 951,439 171 31,045 982,655 Disposals or derecognization - (55,413 ) - (14,594 ) (70,007 ) Disposal of subsidiaries (Note 30) - (38,125 ) - - (38,125 ) Acquisition through business combinations (Note 29) 103,633 1,451,123 - 114,269 1,669,025 Effect of foreign currency exchange differences 552 (66,459 ) 312 (19,160 ) (84,755 ) Balance at December 31, 2020 $ 11,104,186 $ 6,849,443 $ 21,319,179 $ 179,860 $ 39,452,668 Customer Relationships Computer Software Patents and Acquired Specific Technology Others Total NT$ NT$ NT$ NT$ NT$ Accumulated amortization Balance at January 1, 2020 $ 1,666,668 $ 2,677,339 $ 3,600,173 $ 25,303 $ 7,969,483 Amortization expense 1,000,000 729,330 1,998,554 5,493 3,733,377 Disposals or derecognization - (47,345 ) - (5,044 ) (52,389 ) Disposal of subsidiaries (Note 30) - (10,688 ) - - (10,688 ) Acquisition through business combinations (Note 29) 102,768 843,746 - 79,673 1,026,187 Effect of foreign currency exchange differences 547 (21,806 ) 239 (950 ) (21,970 ) Balance at December 31, 2020 $ 2,769,983 $ 4,170,576 $ 5,598,966 $ 104,475 $ 12,644,000 Customer Relationships Computer Software Patents and Acquired Specific Technology Others Total US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) Cost Balance at January 1, 2020 $ 391,738 $ 164,063 $ 759,213 $ 2,432 $ 1,317,446 Additions - 33,883 6 1,106 34,995 Disposals or derecognization - (1,973 ) - (520 ) (2,493 ) Disposal of subsidiaries (Note 30) - (1,358 ) - - (1,358 ) Acquisition through business combinations (Note 29) 3,691 51,678 - 4,069 59,438 Effect of foreign currency exchange differences 20 (2,367 ) 11 (682 ) (3,018 ) Balance at December 31, 2020 $ 395,449 $ 243,926 $ 759,230 $ 6,405 $ 1,405,010 Customer Relationships Computer Software Patents and Acquired Specific Technology Others Total US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) Accumulated amortization Balance at January 1, 2020 $ 59,354 $ 95,347 $ 128,211 $ 901 $ 283,813 Amortization expense 35,613 25,973 71,173 196 132,955 Disposals or derecognization - (1,686 ) - (180 ) (1,866 ) Disposal of subsidiaries (Note 30) - (381 ) - - (381 ) Acquisition through business combinations (Note 29) 3,660 30,048 - 2,837 36,545 Effect of foreign currency exchange differences 19 (776 ) 9 (33 ) (781 ) Balance at December 31, 2020 $ 98,646 $ 148,525 $ 199,393 $ 3,721 $ 450,285 Each class of other intangible assets was amortized on the straight-line basis over the following useful lives: Customer relationships 11 years Computer software 2-10 years Patents and acquired specific technology 5-17 years Others 5-32 years

Borrowings

Borrowings	12 Months Ended
	Dec. 31, 2020
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Borrowings	20. BORROWINGS a. Short-term borrowings Bank loans mainly represented unsecured revolving loans and letters of credit. December 31 2019 2020 NT$ NT$ US$ (Note 4) Secured bank loans, annual interest rate was 0.90%-1.87% as of December 31, 2020 $ - $ 300,495 $ 10,701 Unsecured bank loans, annual interest rates were 0.70%-5.40% and 0.58%-3.83% as of December 31, 2019 and 2020, respectively 40,572,329 34,297,362 1,221,416 40,572,329 34,597,857 1,232,117 Less: financial liabilities for hedging - current (Note 34) 3,233,301 3,307,018 117,771 $ 37,339,028 $ 31,290,839 $ 1,114,346 b. Long-term borrowings 1) Bank loans December 31 2019 2020 NT$ NT$ US$ (Note 4) Revolving bank loans Syndicated bank loans - repayable through April 2021 to October 2022, annual interest rates were 1.80% and 1.15%-1.17% as of December 31, 2019 and 2020 (Note 36) $ 20,000,000 $ 12,536,424 $ 446,454 Others - repayable through January 2021 to July 2029, annual interest rates were 0.82%-4.13% and 0.56%-4.15% as of December 31, 2019 and 2020, respectively 105,214,824 84,146,125 2,996,657 Mortgage loans Repayable through January 2021 to December 2033, annual interest rates were 2.43%-4.90% and 1.90%-4.90% as of December 31, 2019 and 2020, respectively 4,880,822 10,813,997 385,114 130,095,646 107,496,546 3,828,225 Less: unamortized discounts 10,292 104,323 3,715 130,085,354 107,392,223 3,824,510 Less: current portion 5,017,970 2,250,121 80,133 financial liabilities for hedging - current (Note 34) - 1,970,307 70,168 financial liabilities for hedging - non-current (Note 34) - 5,910,919 210,503 $ 125,067,384 $ 97,260,876 $ 3,463,706 Pursuant to some of the above revolving bank loans agreements, the Company and its subsidiaries should meet certain financial covenants which are calculated based on each of their annual audited consolidated financial statements or semi-annual reviewed consolidated financial statements. The Company and its subsidiaries were in compliance with all of the financial covenants. 2) Long-term bills payable December 31 2019 2020 NT$ NT$ US$ (Note 4) Ta Ching Bills Finance Corporation, repayable in March 2022, annual interest rates were 1.01%-1.03% and 0.91% as of December 31, 2019 and 2020, respectively $ 3,100,000 $ 1,000,000 $ 35,613 3) Long-term notes payable - only as of December 31, 2019 December 31, 2019 NT$ Commercial papers $ 100,016 Less: unamortized discounts 2,137 97,879 Less: current portion 94,798 $ 3,081 Annual interest rate (%) 5.02-6.89 The Company’s subsidiary funded from leasing companies by after-sales repurchasing its inventories and machinery which was repaid in October 2020.

Bonds Payable

Bonds Payable	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Bonds Payable	21. BONDS P A December 31 2019 2020 NT$ NT$ US$ (Note 4) Unsecured domestic bonds Repayable at maturity in January 2021 and interest due annually with annual interest rate at 1.30% $ 7,000,000 $ 7,000,000 $ 249,288 December 31 2019 2020 NT$ NT$ US$ (Note 4) Repayable at maturity in January 2023 and interest due annually with annual interest rate at 1.50% $ 2,000,000 $ 2,000,000 $ 71,225 Repayable at maturity in January 2022 and interest due annually with annual interest rate at 1.25% 3,700,000 3,700,000 131,766 Repayable at maturity in January 2024 and interest due annually with annual interest rate at 1.45% 4,300,000 4,300,000 153,134 Repayable at maturity in April 2024 and interest due annually with annual interest rate at 0.90% 6,500,000 6,500,000 231,481 Repayable at maturity in April 2026 and interest due annually with annual interest rate at 1.03% 3,500,000 3,500,000 124,644 Repayable at maturity in April 2025 and interest due annually with annual interest rate at 0.90% - 10,000,000 356,125 Repayable at maturity in August 2023 and interest due annually with annual interest rate at 0.72% - 3,000,000 106,838 Repayable at maturity in August 2025 and interest due annually with annual interest rate at 0.85% - 5,000,000 178,063 Repayable at maturity in August 2027 and interest due annually with annual interest rate at 0.95% - 2,000,000 71,225 Unsecured international bonds US$200,000 thousand (linked to New Taiwan dollar), repayable at maturity in October 2022 and interest due quarterly with annual interest rate at 2.15% 6,204,800 6,204,800 220,969 US$100,000 thousand (linked to New Taiwan dollar), repayable at maturity in October 2024 and interest due quarterly with annual interest rate at 2.50% 3,102,400 3,102,400 110,484 Secured domestic bonds Repayable at maturity in December 2020 and interest due annually with nil annual interest rate 250,000 - - 36,557,200 56,307,200 2,005,242 Less: discounts on bonds payable 35,045 53,646 1,910 36,522,155 56,253,554 2,003,332 Less: current portion of bonds payable 250,000 6,999,951 249,286 $ 36,272,155 $ 49,253,603 $ 1,754,046 a. In December 2017, AMPI offered the fifth secured domestic convertible bonds in NT$250,000 thousand with nil coupon rate and a maturity of 3 years. Each holder of the bonds has the right to convert the bonds into ordinary shares of AMPI at the conversion price at any time from the 3 months after the offering date to the maturity date. The initial conversion price was NT$4.8 per share at offering date and the conversion price will be subject to adjustment in the event of the conversion provisions due to anti-dilution clause. As of December 31, 2019, the conversion prices was NT$4.8 per share. The bonds may be early redeemed at the option of AMPI, in whole or in part, at any time provided that (1) if the closing price of AMPI’s ordinary shares on the Taipei Exchange exceeds the conversion price by 30% or more for 30 consecutive business days in the period starting from 3 months after the offering to 40 days before the maturity or (2) the outstanding amount of the bonds falls below 10% of the originally offered in the period aforementioned. AMPI already redeemed these bonds in December 2020. b. In October 2019, the Company offered the second unsecured international bonds in the aggregate amount of US$300,000 thousand with par value of US$1,000 thousand. These unsecured international bonds were divided into tranche A, in the amount of US$200,000 thousand with maturity of 3 years, and tranche B, in the amount of US$100,000 thousand with maturity of 5 years. The annual interest rates of tranche A and tranche B were 2.15% and 2.50%, respectively. All the proceeds from bonds offering were used to support ASE’s green investments by subscribing for ASE’s newly issued ordinary shares from its private placement.

Other Payables

Other Payables	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Other Payables	22. OTHER PAYABLES December 31 2019 2020 NT$ NT$ US$ (Note 4) Accrued salary and bonus $ 10,384,089 $ 12,448,548 $ 443,324 Payables for property, plant and equipment 14,282,564 10,013,971 356,623 Accrued employees’ compensation and remuneration to directors 3,206,036 4,405,981 156,908 Accrued employee insurance 900,367 1,105,122 39,356 Accrued utilities 504,866 536,491 19,106 Others 9,903,768 10,905,510 388,373 $ 39,181,690 $ 39,415,623 $ 1,403,690

Retirement Benefit Plans

Retirement Benefit Plans	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Retirement Benefit Plans	23. RETIREMENT BENEFIT PLANS a. Defined contribution plan s 1) The pension plan under the R.O.C. Labor Pension Act (“LPA”) for the Group’s R.O.C. resident employees is a government-managed defined contribution plan. Based on the LPA, the Company and its subsidiaries in Taiwan makes monthly contributions to employees’ individual pension accounts at 6% of their monthly salaries. 2) The subsidiaries located in China, U.S.A., Malaysia, Korea, Singapore and Mexico also make contributions at various ranges according to relevant local regulations. b. Defined benefit plans 1) The Company and its subsidiaries in Taiwan joined the defined benefit pension plan under the R.O.C. Labor Standards Law operated by the government. Pension benefits are calculated on the basis of the length of service and average monthly salaries of the last six months before retirement. The Company and its subsidiaries in Taiwan make contributions based on a certain percentage of their domestic employees’ monthly salaries to a pension fund administered by the pension fund monitoring committee. Before the end of each year, the Company and its subsidiaries in Taiwan assess the balance in the pension fund. If the amount of the balance in the pension fund is inadequate to pay retirement benefits for employees who conform to retirement requirements in the next year, the Company and its subsidiaries in Taiwan are required to fund the difference in one appropriation that should be made by the end of March in the next year. Pension contributions are deposited in the Bank of Taiwan in the committee’s name and are managed by the Bureau of Labor Funds, Ministry of Labor (“the Bureau”); the Company and its subsidiaries in Taiwan have no right to influence the investment policy and strategy. 2) ASE Japan has a pension plan under which eligible employees with more than a year of service are entitled to receive pension benefits based on their length of service and salaries at the time of termination of employment. ASE Korea has a pension plan under which eligible employees and directors with more than one year of service are entitled to receive a lump-sum payment upon termination of their service with ASE Korea, based on their length of service and salaries at the time of termination. ASE Korea makes contributions based on a certain percentage of employees’ salaries to an external financial institution in the names of employees and were administered by the management. USIPL’s pension plan stipulates that employees, who meet retirement criteria and terminate their employments due to retirement, are entitled to receive a pension of a month salary at the time of retirement; ASTEELFLASH GERMANY GmbH’s, ASTEELFLASH HERSFELD GmbH’s and ASTEELFLASH BONN GmbH ’s pension plans stipulate that employees with more than ten years of service are entitled to receive a lump-sum payment based on their length of service and the salaries of the most recent ten years at the time of termination of employment. FINANCIERE AFG’s, ASTEELFLASH GROUP’s, ASTEELFLASH TECHNOLOGIE’s and ASTEELFLASH FRANCE’s pension plans stipulate that employees with more than two years of service are entitled to receive a lump-sum payment based on their length of service and the salaries of the most recent twelve months at the time of termination of employment. 3) ASE, SPIL, ASE Test, Inc. and ASE Electronics Inc. maintain pension plans for executive managers. Pension costs under the plans were NT$11,137 thousand, NT$11,567 thousand and NT$11,184 thousand (US$398 thousand) for the years ended December 31, 2018, 2019 and 2020, respectively. As of December 31, 2019 and 2020, accrued pension liabilities for executive managers were NT$335,109 thousand and NT346,015 thousand (US$12,322 thousand), respectively. 4) The amounts included in the consolidated balance sheets arising from the Group’s obligation in respect of its defined benefit plans excluding those for executive managers were as follows: December 31 2019 2020 NT$ NT$ US$ (Note 4) Present value of the defined benefit obligation $ 10,668,574 $ 12,159,145 $ 433,018 Fair value of the plan assets (5,742,178 ) (5,962,305 ) (212,333 ) Present value of unfunded defined benefit obligation 4,926,396 6,196,840 220,685 Recorded under other payables (19,014 ) (102,367 ) (3,646 ) Recorded under other non-current assets 11,910 26,306 937 Net defined benefit liability $ 4,919,292 $ 6,120,779 $ 217,976 Movements in net defined benefit liability (asset) were as follows: Present Value of the Defined Benefit Obligation Fair Value of the Plan Assets Net Defined Benefit Liability (Asset) NT$ NT$ NT$ Balance at January 1, 2018 $ 7,910,638 $ (4,341,373 ) $ 3,569,265 Service cost Current service cost 224,126 - 224,126 Net interest expense (income) 178,779 (122,709 ) 56,070 Recognized in profit or loss 402,905 (122,709 ) 280,196 Remeasurement Return on plan assets (excluding amounts included in net interest) - (16,589 ) (16,589 ) Actuarial (gain) loss Changes in financial assumptions (8,643 ) - (8,643 ) Experience adjustments 302,499 - 302,499 Changes in demographic assumptions 8,190 - 8,190 Changes in other assumptions 22,723 - 22,723 Recognized in other comprehensive income 324,769 (16,589 ) 308,180 Contributions from the employer - (364,237 ) (364,237 ) Benefits paid from the pension fund (541,989 ) 541,989 - the Group (295,953 ) - (295,953 ) Business combinations 2,522,805 (1,210,524 ) 1,312,281 Exchange differences on foreign plans (26,036 ) 21,320 (4,716 ) Balance at December 31, 2018 10,297,139 (5,492,123 ) 4,805,016 Service cost Current service cost 211,226 - 211,226 Net interest expense (income) 151,635 (97,387 ) 54,248 Recognized in profit or loss 362,861 (97,387 ) 265,474 Remeasurement Return on plan assets (excluding amounts included in net interest) - (104,516 ) (104,516 ) Actuarial (gain) loss Changes in financial assumptions 398,732 - 398,732 Experience adjustments 70,374 - 70,374 Changes in demographic assumptions (2,329 ) - (2,329 ) Recognized in other comprehensive income 466,777 (104,516 ) 362,261 Present Value of the Defined Benefit Obligation Fair Value of the Plan Assets Net Defined Benefit Liability (Asset) NT$ NT$ NT$ Contributions from the employer $ - $ (514,617 ) $ (514,617 ) Benefits paid from the pension fund (393,897 ) 393,897 - the Group (21,439 ) - (21,439 ) Business combinations 62,857 (28,380 ) 34,477 Exchange differences on foreign plans (105,724 ) 100,948 (4,776 ) Balance at December 31, 2019 $ 10,668,574 $ (5,742,178 ) $ 4,926,396 Service cost Current service cost 193,693 - 193,693 Past service cost and gain on settlements (25,891 ) - (25,891 ) Net interest expense (income) 119,314 (81,114 ) 38,200 Recognized in profit or loss 287,116 (81,114 ) 206,002 Remeasurement Return on plan assets (excluding amounts included in net interest) - (109,616 ) (109,616 ) Actuarial (gain) loss Changes in financial assumptions 465,433 - 465,433 Experience adjustments 281,661 - 281,661 Changes in demographic assumptions (36,627 ) - (36,627 ) Recognized in other comprehensive income 710,467 (109,616 ) 600,851 Contributions from the employer - (620,433 ) (620,433 ) Benefits paid from the pension fund (552,430 ) 603,137 50,707 the Group (14,520 ) - (14,520 ) Assets extinguished on settlement - 11,910 11,910 Business combinations 1,018,480 - 1,018,480 Exchange differences on foreign plans 41,458 (24,011 ) 17,447 Balance at December 31, 2020 $ 12,159,145 $ (5,962,305 ) $ 6,196,840 Present Value of the Defined Benefit Obligation Fair Value of the Plan Assets Net Defined Benefit Liability (Asset) US$ (Note 4) US$ (Note 4) US$ (Note 4) Balance at January 1, 2020 $ 379,935 $ (204,493 ) $ 175,442 Service cost Current service cost 6,898 - 6,898 Present Value of the Defined Benefit Obligation Fair Value of the Plan Assets Net Defined Benefit Liability (Asset) US$ (Note 4) US$ (Note 4) US$ (Note 4) Past service cost and gain on settlements $ (922 ) $ - $ (922 ) Net interest expense (income) 4,249 (2,889 ) 1,360 Recognized in profit or loss 10,225 (2,889 ) 7,336 Remeasurement Return on plan assets (excluding amounts included in net interest) - (3,904 ) (3,904 ) Actuarial (gain) loss Changes in financial assumptions 16,575 - 16,575 Experience adjustments 10,031 - 10,031 Changes in demographic assumptions (1,304 ) - (1,304 ) Recognized in other comprehensive income 25,302 (3,904 ) 21,398 Contributions from the employer - (22,095 ) (22,095 ) Benefits paid from the pension fund (19,673 ) 21,479 1,806 the Group (517 ) - (517 ) Assets extinguished on settlement - 424 424 Business combinations 36,270 - 36,270 Exchange differences on foreign plans 1,476 (855 ) 621 Balance at December 31, 2020 $ 433,018 $ (212,333 ) $ 220,685 5) The fair value of the plan assets by major categories at each balance sheet date was as follows: December 31 2019 2020 NT$ NT$ US$ (Note 4) Cash $ 2,396,657 $ 2,236,340 $ 79,642 Equity instruments 2,315,637 2,459,708 87,596 Debt instruments 1,029,884 1,092,115 38,893 Others - 174,142 6,202 Total $ 5,742,178 $ 5,962,305 $ 212,333 6) Through the defined benefit plans under the Labor Standards Law of the R.O.C., the Group in Taiwan are exposed to the following risks: a) Investment risk The plan assets are invested in equity and debt securities, bank deposits, etc. The investment is conducted at the discretion of the Bureau or under the mandated management. However, in accordance with relevant regulations, the return generated by plan assets should not be below the interest rate for a 2-year time deposit with local banks. b) Interest risk A decrease in the government bond interest rate will increase the present value of the defined benefit obligation; however, this will be partially offset by an increase in the return on the plan’s debt investments. c) Salary risk The present value of the defined benefit obligation is calculated by reference to the future salaries of plan participants. As such, an increase in the salary of the plan participants will increase the present value of the defined benefit obligation. 7) The management of ASE Korea is responsible for the administration of the fund and determination of the investment strategies according to related local regulations. ASE Korea is responsible for the shortfall between the fund and the defined benefit obligation. The plan assets are invested in the certificates of deposits. 8) The present value of the defined benefit obligation and the related current service cost and past service cost were measured using the Projected Unit Credit Method. Except the pension plans for executive managers, the key assumptions used for the actuarial valuations were as follow: December 31 2019 2020 Discount rates (%) 0.08-2.85 0.00-2.77 Expected rates of salary increase (%) 1.00-4.01 1.00-4.06 The sensitivity analysis below has been determined based on reasonably possible changes of the respective assumptions occurring at each balance sheet date, while holding all other assumptions constant. December 31 2019 2020 NT$ NT$ US$ (Note 4) Discount Rate 0.5% higher $ (555,266 ) $ (617,803 ) $ (22,002 ) 0.5% lower $ 601,616 $ 600,451 $ 21,384 Expected rates of salary increase 0.5% higher $ 591,915 $ 611,217 $ 21,767 0.5% lower $ (545,528 ) $ (565,555 ) $ (20,141 ) The sensitivity analysis presented above may not be representative of the actual change in the defined benefit obligation as it is unlikely that the change in assumptions would occur in isolation of one another as some of the assumptions may be correlated. 9) Maturit y December 31 2019 2020 NT$ NT$ US$ (Note 4) No later than 1 year $ 422,067 $ 498,092 $ 17,738 Later than 1 year but not later than 5 years 2,081,540 2,553,522 90,937 Later than 5 years 12,216,422 12,325,576 438,945 $ 14,720,029 $ 15,377,190 $ 547,620 The Group expected to make contributions of NT$533,777 thousand and NT$513,781 thousand (US$18,297 thousand) to the defined benefit plans in the next year starting from January 1, 2020 and 2021, respectively. As of December 31, 2019 and 2020, the average duration of the defined benefit obligation excluding those for executive managers of the Group was 10 to 14 years and 9 to 16 years, respectively.

Equity

Equity	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Equity	24. EQUITY a. Share capita l Ordinary shares December 31 2019 2020 Numbers of shares authorized (in thousands) 5,000,000 5,500,000 Numbers of shares reserved (in thousands) Employee share options 400,000 400,000 Number of shares issued and fully paid (in thousands) 4,330,528 4,351,592 December 31 2019 2020 NT$ NT$ US$ (Note 4) Share capital authorized $ 50,000,000 $ 55,000,000 $ 1,958,689 Share capital reserved Employee share options $ 4,000,000 $ 4,000,000 $ 142,450 Share capital issued and fully paid $ 43,305,287 $ 43,515,920 $ 1,549,712 American Depositary Receipts The Company’s ADS represents 2 ordinary shares of the Company. As of December 31, 2019 and 2020, 125,542 thousand and 107,964 thousand ADSs were outstanding and represented approximately 251,084 thousand and 215,927 thousand ordinary shares of the Company, respectively. b. Capital surplus December 31 2019 2020 NT$ NT$ US$ (Note 4) May be used to offset a deficit, distributed as cash dividends, or transferred to share capital (1) Issuance of ordinary shares $ 13,070,330 $ 13,548,426 $ 482,494 Merger by share exchange 117,693,658 117,693,658 4,191,369 (Continued) December 31 2019 2020 NT$ NT$ US$ (Note 4) Difference between consideration and the carrying amount of the subsidiaries’ net assets during actual disposal or acquisition $ 3,254,489 $ 3,240,987 $ 115,420 134,018,477 134,483,071 4,789,283 May be used to offset a deficit only Changes in percentage of ownership interest in subsidiaries (2) 891,876 1,451 52 Treasury share transactions 364,708 510,449 18,178 Exercised employee share options 1,443,995 1,617,254 57,595 Expired share options (Note 28) 645,903 645,903 23,002 Share of changes in capital surplus of associates 16,266 41,239 1,469 Dividends that the claim period has elapsed and unclaimed by shareholders 1,942 3,550 126 3,364,690 2,819,846 100,422 May not be used for any purpose Employee share options 1,304,250 1,894,952 67,484 Others (3) 222,946 569,681 20,288 1,527,196 2,464,633 87,772 $ 138,910,363 $ 139,767,550 $ 4,977,477 (Concluded) 1) Such capital surplus may be used to offset a deficit; in addition, when the Company has no deficit, such capital surplus may be distributed as cash dividends or transferred to share capital (limited to a certain percentage of the Company’s capital surplus and once a year). 2) Such capital surplus arises from the effects of changes in ownership interests in subsidiaries resulting from equity transactions other than actual disposals or acquisitions, or from changes in capital surplus of subsidiaries accounted for using the equity method. 3) Such capital surplus represents the excess of the carrying amount of related accounts over the par value due to employee share options exercised and the Company has not completed registration formalities. c. Retained earnings and dividend policy The Articles of Incorporation of the Company (the “Articles”) provides that annual net income shall be distributed in the following order: 1) Replenishment of deficits; 2) 10.0% as legal reserve; 3) Special reserve appropriated or reversed in accordance with laws or regulations set forth by the authorities concerned; 4) If annual net income remains, a proposal for the distribution of such amount together with a part or all of the accumulated undistributed profits in previous years shall be prepared by the board of directors and submit to the shareholders’ meeting for resolution. For the policies on the distribution of employees’ compensation and remuneration of directors, refer to employees’ compensation and remuneration of directors in Note 25(g). The Company is currently in the mature growth stage. To meet the capital needs for business development now and in the future and satisfy the shareholders’ demand for cash inflows, the Company shall use residual dividend policy to distribute dividends, of which the cash dividend is not lower than 30% of the total dividend distribution, with the remainder to be distributed in shares. A distribution plan is also to be made by the board of directors and passed for resolution in the shareholders’ meeting. Appropriation of earnings to legal reserve shall be made until the legal reserve equals the Company’s share capital. Legal reserve may be used to offset deficits. If the Company has no deficit and the legal reserve has exceeded 25% of the Company’s share capital, the excess may be transferred to capital or distributed in cash. Items referred to under Rule No. 1010012865 and Rule No. 1010047490 issued by the Financial Supervisory Commission R.O.C. and in the directive titled “Questions and Answers for Special Reserves Appropriated Following Adoption of IFRSs” should be appropriated to or reversed from a special reserve by the Company. The appropriation of earnings for 2018 and 2019 resolved at the Company’s annual shareholders’ meetings in June 2019 and June 2020, respectively were as follows: Appropriation of Earnings Dividends Per Share For Year 2018 For Year 2019 For Year 2018 For Year 2019 NT$ NT$ NT$ NT$ (in dollars) (in dollars) Legal reserve $ 2,203,895 $ 1,697,489 Special reserve 3,548,844 3,944,915 Cash dividends 10,806,454 8,668,331 $ 2.5 $ 2.0 $ 16,559,193 $ 14,310,735 d. Others equity items 1) Exchange differences on translating foreign operations For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Balance at January 1 $ (6,733,659 ) $ (5,888,574 ) $ (10,762,684 ) $ (383,286 ) Recognized for the year Exchange differences on translating foreign operations 426,186 (4,788,135 ) (1,173,204 ) (41,781 ) (Continued) For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Share from associates and joint venture accounted for using the equity method $ 136,608 $ (85,975 ) $ 101,038 $ 3,598 Reclassification adjustments Disposal of associates and joint venture accounted for using the equity method 282,291 - 29,971 1,067 Disposal of foreign operations - - 162,940 5,803 Balance at December 31 $ (5,888,574 ) $ (10,762,684 ) $ (11,641,939 ) $ (414,599 ) (Concluded) 2) Unrealized gain (loss) on financial assets at FVTOCI For the Year Ended December 31 2019 2020 NT$ NT$ US$ (Note 4) Balance at January 1 $ (1,015,107 ) $ (203,098 ) $ (7,233 ) Unrealized gain (loss) recognized during the year Debt instruments (2,052 ) (2,136 ) (76 ) Equity instruments (283,472 ) (405,020 ) (14,424 ) Share from associates and joint venture accounted for using the equity method 1,501,689 2,655,570 94,572 Realized gain (loss) recognized during the year Share from the disposal of associates and joint venture accounted for using the equity method - 1,094 39 Equity instruments - 16,383 583 Share from associates and joint venture accounted for using the equity method (404,156 ) (34,891 ) (1,242 ) Balance at December 31 $ (203,098 ) $ 2,027,902 $ 72,219 3) Gain (loss) on hedging instruments - hedges of net investments of foreign operations For the year ended December 31, 2020 NT$ US$ (Note 4) Balance at January 1 $ - $ - Recognized during the period Foreign currency risk – loans denominated in foreign currency (429,265 ) (15,287 ) Balance at December 31 $ (429,265 ) $ (15,287 ) e. Treasury shares (in thousand shares) The Company’s shares held by subsidiaries both were 72,941 thousand shares for the years ended December 31, 2019 and 2020. The Company’s shares held by its subsidiaries at each balance sheet date were as follows: Shares Held by Subsidiaries Carrying Amount Carrying Amount Fair Value Fair Value (in thousand shares) NT$ US$ (Note 4) NT$ US$ (Note 4) December 31, 2019 ASE Test 44,100 $ 1,380,721 $ 3,669,140 J&R Holding 23,352 381,709 1,942,876 ASE Test, Inc. 5,489 196,677 456,717 72,941 $ 1,959,107 $ 6,068,733 December 31, 2020 ASE Test 44,100 $ 1,380,721 $ 49,171 $ 3,585,349 $ 127,683 J&R Holding 23,352 381,709 13,594 1,898,508 67,611 ASE Test, Inc. 5,489 196,677 7,004 446,287 15,893 72,941 $ 1,959,107 $ 69,769 $ 5,930,144 $ 211,187 Fair value (Level 1) of the Company’s shares held by subsidiaries is based on the closing price from an available published price quotation. The subsidiaries holding the aforementioned treasury shares retain shareholders’ rights except the rights to participate in any capital increase by cash and voting. f. Non-controlling interests For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Balance at January 1 $ 13,195,312 $ 17,639,487 $ 13,374,912 $ 476,315 Share of profit for the year 1,203,588 1,207,974 1,681,320 59,876 Other comprehensive income (loss) Exchange difference on translating foreign operations (198,365 ) (414,010 ) 178,480 6,356 Unrealized (loss) gain on equity instruments at FVTOCI (23,928 ) (10,773 ) 1,321 47 Loss from hedging - - (145,559 ) (5,184 ) Remeasurement on defined benefit plans (30,079 ) (7,422 ) (9,075 ) (323 ) Non-controlling interests arising from acquisition or disposal of subsidiaries (Note 29) 3,582,866 666,651 (5,658 ) (202 ) Subscribing for ordinary shares from subsidiaries’ cash capital increase - 83,044 - - Acquisition of non-controlling interests in subsidiaries (Note 31) (2,492,915 ) (5,084,785 ) (116,738 ) (4,157 ) Issuance of new ordinary shares by subsidiaries (Note 29) - - 1,711,453 60,949 Partial disposal of subsidiaries 1,693,064 - - - Subsidiaries’ buy back of their own outstanding ordinary shares (Note 31) (801,884 ) (2,017,319 ) (2,299,533 ) (81,892 ) Non-controlling interest relating to outstanding vested employee share options granted by subsidiaries 1,936,643 1,672,310 1,591,904 56,692 Cash dividends to non-controlling interests (424,815 ) (360,245 ) (346,774 ) (12,350 ) Balance at December 31 $ 17,639,487 $ 13,374,912 $ 15,616,053 $ 556,127

Profit Before Income Tax

Profit Before Income Tax	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Profit Before Income Tax	25. PROFIT BEFORE INCOME TAX a. Other operating income and expenses, net For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Rental income $ 182,411 $ 136,301 $ 153,682 $ 5,473 Gains (losses) on disposal of property, plant and equipment and other assets (14,644 ) (164,187 ) 732,796 26,097 Impairment losses on property, plant and equipment (Note 15) (133,071 ) (201,006 ) (992,273 ) (35,337 ) Loss on damages and claims (24,114 ) (459,544 ) (176,888 ) (6,299 ) Others 361,001 419,881 785,175 27,961 $ 371,583 $ (268,555 ) $ 502,492 $ 17,895 b. Other income For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Government subsidy $ 435,950 $ 624,351 $ 803,049 $ 28,599 Interest income 466,211 549,681 520,783 18,546 Dividends income 190,397 185,061 150,715 5,367 $ 1,092,558 $ 1,359,093 $ 1,474,547 $ 52,512 c. Other gains, net For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Remeasurement gain on investments accounted for using the equity method due to step acquisition (Note 29) $ 7,421,408 $ 319,712 $ - $ - Net gains on financial assets mandatorily at FVTPL 3,388,485 3,631,763 3,211,125 114,356 Net losses arising on financial instruments held for trading (1,398,995 ) (1,984,941 ) (3,282,973 ) (116,915 ) Gain on disposal of subsidiaries (Note 30) - - 802,753 28,588 Foreign exchange gains (losses), net (1,015,615 ) 1,125,681 1,005,374 35,805 Gain on disposal of investments accounted for using the equity method (Note 14) - - 91,297 3,251 Impairment losses on financial assets (Note 14) (521,010 ) (400,201 ) - - Others - (8,025 ) - - $ 7,874,273 $ 2,683,989 $ 1,827,576 $ 65,085 d. Finance costs For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Interest on lease liabilities $ - $ 88,742 $ 88,026 $ 3,135 Interest on borrowings and bonds payable 3,597,932 4,211,541 3,498,999 124,608 Total interest expense for financial liabilities measured at amortized cost 3,597,932 4,300,283 3,587,025 127,743 Less: Amounts included in the cost of qualifying assets Inventories related to real estate business (11,648 ) (35,713 ) (95,589 ) (3,404 ) Property, plant and equipment (50,309 ) (77,715 ) (54,208 ) (1,930 ) Investment properties (89 ) - - - 3,535,886 4,186,855 3,437,228 122,409 Other finance costs 32,355 16,540 22,283 793 $ 3,568,241 $ 4,203,395 $ 3,459,511 $ 123,202 Information relating to the capitalized borrowing costs was as follows: For the Year Ended December 31 2018 2019 2020 Annual interest capitalization rates Inventories related to real estate business (%) 4.35 4.35-4.85 4.20-4.75 Property, plant and equipment (%) 1.84-4.52 0.96-4.03 0.49-3.47 Investment properties (%) 1.84-2.23 - - e. Depreciation and amortization For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Property, plant and equipment $ 39,893,786 $ 45,240,667 $ 46,016,548 $ 1,638,766 Right-of-use assets - 1,055,458 946,880 33,721 Investment properties 392,667 594,110 562,260 20,023 Other intangible assets 2,402,450 3,576,606 3,733,377 132,955 Total $ 42,688,903 $ 50,466,841 $ 51,259,065 $ 1,825,465 Summary of depreciation by function Operating costs $ 37,903,050 $ 43,749,333 $ 44,017,839 $ 1,567,587 Operating expenses 2,383,403 3,140,902 3,507,849 124,923 $ 40,286,453 $ 46,890,235 $ 47,525,688 $ 1,692,510 For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Summary of amortization by function Operating costs $ 1,394,664 $ 2,092,074 $ 2,231,060 $ 79,454 Operating expenses 1,007,786 1,484,532 1,502,317 53,501 $ 2,402,450 $ 3,576,606 $ 3,733,377 $ 132,955 Operating expenses directly related to investment properties For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Direct operating expenses of investment properties that generated rental income $ 1,276,751 $ 1,232,826 $ 1,121,854 $ 39,952 f. Employee benefits expense For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Post-employment benefits Defined contribution plans $ 2,965,054 $ 3,148,209 $ 2,979,167 $ 106,096 Defined benefit plans 291,333 277,041 217,186 7,735 3,256,387 3,425,250 3,196,353 113,831 Equity-settled share-based payments 215,648 871,699 955,575 34,030 Other employee benefits 63,940,430 70,279,752 76,648,412 2,729,644 $ 67,412,465 $ 74,576,701 $ 80,800,340 $ 2,877,505 Summary of employee benefits expense by function Operating costs $ 45,363,170 $ 49,173,778 $ 52,526,164 $ 1,870,590 Operating expenses 22,049,295 25,402,923 28,274,176 1,006,915 $ 67,412,465 $ 74,576,701 $ 80,800,340 $ 2,877,505 g. Employees’ compensation and the remuneration to directors The Articles stipulates to distribute employees’ compensation and remuneration to directors at the rates in 0.01%-1.00% and no higher than 0.75%, respectively, of net profit before income tax, employees’ compensation and remuneration to directors. For the Year Ended December 31 2019 2020 Accrual Rate (%) Accrual Amount Accrual Rate (%) Accrual Amount NT$ NT$ US$ (Note 4) Employees’ compensation 0.20 $ 34,400 0.20 $ 54,909 $ 1,955 Remuneration to directors 0.40 68,803 0.40 109,818 3,911 If there is a change in the proposed amounts after the consolidated financial statement authorized for issue, the differences are recorded as a change in accounting estimate and will be adjusted in the following year. In March 2019 and 2020, the board of directors resolved the appropriations of employees’ compensation and remuneration to directors in cash for 2018 and 2019, respectively. The differences between the resolved amounts and the accrued amounts reflected in the annual consolidated financial statements for the years ended December 31, 2018 and 2019 were deemed changes in estimates. The differences were both NT$3 thousand (US$0.1 thousand) and were adjusted in net profit for each of the year ended December 31, 2019 and 2020, respectively. For Year 2018 For Year 2019 Employees’ compensation Remuneration to directors Employees’ compensation Remuneration to directors NT$ NT$ NT$ NT$ Resolved by the board of directors $ 45,430 $ 34,070 $ 34,400 $ 68,800 Recognized in the consolidated financial statements $ 45,430 $ 34,073 $ 34,400 $ 68,803 Information on the employees’ compensation and the remuneration to directors resolved by the board of directors is available at the Market Observation Post System website of the Taiwan Stock Exchange (the “TWSE”).

Income Tax

Income Tax	12 Months Ended
	Dec. 31, 2020
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Income Tax	26. INCOME TAX The Company and its subsidiaries have filed a consolidated tax return for corporate income tax starting from 2019 and for unappropriated earnings starting from 2018. a. Income tax recognized in profit or loss The major components of income tax were as follows: For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Current income tax In respect of the current year $ 5,207,309 $ 5,002,954 $ 6,807,882 $ 242,446 Income tax on unappropriated earnings (1,022,560 ) 19,115 680,649 24,240 Changes in estimate for prior years (103,822 ) (352,579 ) (472,512 ) (16,827 ) 4,080,927 4,669,490 7,016,019 249,859 (Continued) For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Deferred income tax In respect of the current year $ (227,327 ) $ 563,512 $ 212,338 $ 7,562 Effect of tax rate changes 657,346 54,072 - - Changes in estimate for prior years 5,696 (213,758 ) (103,021 ) (3,669 ) Effect of foreign currency exchange differences (3,273 ) (62,070 ) (8,438 ) (301 ) 432,442 341,756 100,879 3,592 Income tax expense recognized in profit or loss $ 4,513,369 $ 5,011,246 $ 7,116,898 $ 253,451 (Concluded) A reconciliation of income tax expense calculated at the statutory rates and income tax expense recognized in profit or loss was as follows: For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Profit before income tax $ 31,937,678 $ 23,279,811 $ 35,768,798 $ 1,273,817 Income tax expense calculated at the statutory rates $ 13,540,599 $ 11,802,811 $ 16,907,904 $ 602,133 Nontaxable expense in determining taxable income 353,019 459,133 316,619 11,276 Tax-exempt income (2,515,453 ) (495,883 ) (387,212 ) (13,790 ) Additional income tax on unappropriated earnings (1,022,560 ) 19,115 680,649 24,240 Loss carry-forward and income tax credits currently used (971,124 ) (898,198 ) (1,191,387 ) (42,428 ) Remeasurement of deferred income tax assets, net (4,776,271 ) (5,588,335 ) (8,650,569 ) (308,069 ) Changes in estimate for prior periods (103,822 ) (352,579 ) (472,512 ) (16,827 ) Unrecognized deductible temporary differences - - (138,890 ) (4,946 ) Withholding tax 8,981 65,182 52,296 1,862 Income tax expense recognized in profit or loss $ 4,513,369 $ 5,011,246 $ 7,116,898 $ 253,451 In July 2019, the President of the R.O.C. announced the amendments to the Statute for Industrial Innovation, which stipulate that the amounts of unappropriated earnings in 2018 and thereafter that are reinvested in the construction or purchase of certain assets or technologies are allowed as deduction when computing the income tax on unappropriated earnings. When calculating the tax on unappropriated earnings, the Group only deducts the amount of the unappropriated earnings that has been reinvested in capital expenditure. In addition, in accordance with Rule No.10904558730 issued by the Ministry of Finance of Taiwan (MOF), the Group has deducted the amount of dividends distributed in 2020 attributable to the increase in the retained earnings as of January 1, 2018 as a result of initial adoption of IFRS 9 and IFRS 15 when calculating the tax on unappropriated earnings for 2018. b. Income tax recognized directly in equity For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Deferred income tax Related to employee share options $ (1,099 ) $ 1,404 $ (1,159 ) $ (41 ) c. Income tax recognized in other comprehensive income For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Deferred income tax Related to remeasurement of defined benefit plans $ 55,346 $ 74,308 $ 114,559 $ 4,080 Unrealized loss on equity instruments at fair value through other comprehensive income - (78,124 ) (237,460 ) (8,457 ) Effect of tax rate changes 70,755 - - - Income tax recognized in other comprehensive income $ 126,101 $ (3,816 ) $ (122,901 ) $ (4,377 ) d. Current tax assets and liabilities December 31 2019 2020 NT$ NT$ US$ (Note 4) Current tax assets Tax refund receivable $ 90,569 $ 303,265 $ 10,800 Prepaid income tax 462,523 399,555 14,229 $ 553,092 $ 702,820 $ 25,029 Current tax liabilities Income tax payable $ 4,858,578 $ 6,514,502 $ 231,998 e. Deferred tax assets and liabilities The Group offset certain deferred tax assets and deferred tax liabilities which met the offset criteria. The movements of deferred tax assets and deferred tax liabilities were as follows: For the year ended December 31, 2018 Balance at January 1 Adjustment on initial Application of IFRS 15 Recognized in Profit or Loss Recognized in Other Comprehensive Income Recognized in Equity Exchange Differences Acquisitions Through Business Combinations Balance at December 31 NT$ NT$ NT$ NT$ NT$ NT$ NT$ NT$ Deferred tax assets (liabilities) Temporary differences Property, plant and equipment $ (3,879,066 ) $ - $ (600,229 ) $ - $ - $ (21,146 ) $ (45,873 ) $ (4,546,314 ) Defined benefit obligation 780,240 - (131,687 ) 126,101 - 27,884 262,286 1,064,824 FVTPL financial instruments (104,903 ) - 284,659 - - (137 ) 27,402 207,021 Others 1,028,409 (97,358 ) (26,147 ) - (1,099 ) 74,327 294,540 1,272,672 (2,175,320 ) (97,358 ) (473,404 ) 126,101 (1,099 ) 80,928 538,355 (2,001,797 ) Loss carry-forward 681,441 - (50,059 ) - - 28,293 12,600 672,275 Investment credits 534,213 - 91,021 - - 5,932 - 631,166 $ (959,666 ) $ (97,358 ) $ (432,442 ) $ 126,101 $ (1,099 ) $ 115,153 $ 550,955 $ (698,356 ) For the year ended December 31, 2019 Balance at January 1 Recognized in Profit or Loss Recognized in Other Comprehensive Income Recognized in Equity Exchange Differences Acquisitions through Business Combinations Balance at December 31 NT$ NT$ NT$ NT$ NT$ NT$ NT$ Deferred tax assets (liabilities) Temporary differences Property, plant and equipment $ (4,546,314 ) $ (80,593 ) $ - $ - $ (17,949 ) $ (16,917 ) $ (4,661,773 ) Defined benefit obligation 1,064,824 (57,746 ) 74,308 - (2,803 ) - 1,078,583 FVTPL financial instruments 207,021 43,285 - - 9 - 250,315 Others 1,272,672 6,148 (78,124 ) 1,404 (21,763 ) 8,184 1,188,521 (2,001,797 ) (88,906 ) (3,816 ) 1,404 (42,506 ) (8,733 ) (2,144,354 ) Loss carry-forward 672,275 (166,128 ) - - (12,203 ) 48,837 542,781 Investment credits 631,166 (86,722 ) - - (7,404 ) - 537,040 $ (698,356 ) $ (341,756 ) $ (3,816 ) $ 1,404 $ (62,113 ) $ 40,104 $ (1,064,533 ) For the year ended December 31, 2020 Balance at January 1 Recognized in Profit or Loss Recognized in Other Comprehensive Income Recognized in Equity Exchange Differences Acquisitions through Business Combinations Disposal of Subsidiaries Balance at December 31 NT$ NT$ NT$ NT$ NT$ NT$ NT$ NT$ Deferred tax assets (liabilities) Temporary differences Property, plant and equipment $ (4,661,773 ) $ (422,833 ) $ - $ - $ 43,364 $ 21,875 $ (13,982 ) $ (5,033,349 ) Defined benefit obligation 1,078,583 (36,633 ) 114,559 - 1,005 212,941 - 1,370,455 FVTPL financial instruments 250,315 (135,103 ) - - (74 ) 2,085 (11,281 ) 105,942 Others 1,188,521 624,442 (237,460 ) (1,159 ) (42,771 ) 114,036 (119,564 ) 1,526,045 (2,144,354 ) 29,873 (122,901 ) (1,159 ) 1,524 350,937 (144,827 ) (2,030,907 ) Loss carry-forward 542,781 (44,651 ) - - (915 ) 183,045 (152,594 ) 527,666 Investment credits 537,040 (86,100 ) - - (21,559 ) - - 429,381 $ (1,064,533 ) $ (100,878 ) $ (122,901 ) $ (1,159 ) $ (20,950 ) $ 533,982 $ (297,421 ) $ (1,073,860 ) Balance at January 1 Recognized in Profit or Loss Recognized in Other Comprehensive Income Recognized in Equity Exchange Differences Acquisitions through Business Combinations Disposal of Subsidiaries Balance at December 31 US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) Deferred tax assets (liabilities) Temporary differences Property, plant and equipment $ (166,018 ) $ (15,058 ) $ - $ - $ 1,544 $ 779 $ (498 ) $ (179,251 ) Defined benefit obligation 38,411 (1,305 ) 4,080 - 36 7,583 - 48,805 FVTPL financial instruments 8,914 (4,811 ) - - (3 ) 74 (402 ) 3,772 Others 42,328 22,238 (8,457 ) (41 ) (1,523 ) 4,061 (4,258 ) 54,348 (76,365 ) 1,064 (4,377 ) (41 ) 54 12,497 (5,158 ) (72,326 ) Loss carry-forward 19,330 (1,590 ) - - (33 ) 6,519 (5,434 ) 18,792 Investment credits 19,125 (3,066 ) - - (768 ) - - 15,291 $ (37,910 ) $ (3,592 ) $ (4,377 ) $ (41 ) $ (747 ) $ 19,016 $ (10,592 ) $ (38,243 ) f. Items for which no deferred tax assets have been recognized for loss carry-forward, investment credits and deductible temporary differences December 31 2019 2020 NT$ NT$ US$ (Note 4) Loss carry-forward $ 966,783 $ 1,497,056 $ 53,314 Investment credits 51,217 49,611 1,767 Deductible temporary differences 446,754 377,242 13,434 $ 1,464,754 $ 1,923,909 $ 68,515 The unrecognized loss carry-forward will expire through 2030. g. Information about unused loss carry-forward, unused investment credits, tax-exemption and other tax relief As of December 31, 2020, the unused loss carry-forward comprised of: Expiry Year NT$ US$ (Note 4) 2021 $ 79,849 $ 2,844 2022 140,029 4,987 2023 192,607 6,859 2024 172,337 6,137 2025 and thereafter 1,439,900 51,279 $ 2,024,722 $ 72,106 As of December 31, 2020, unused investment credits comprised of: Tax Credit Source Remaining Creditable Amount Expiry Year NT$ US$ (Note 4) Purchase of machinery and equipment $ 405,188 $ 14,430 2027 Others 73,804 2,628 2026 and thereafter $ 478,992 $ 17,058 As of December 31, 2020, profits attributable to the following expansion projects were exempted from income tax for a 5-year pe r d Tax-exemption Period Construction and expansion of ASE Test Inc. in 2009 2018.01-2022.12 Some China subsidiaries qualified as high technology enterprise s h. Unrecognized deferred tax liabilities associated with investments As of December 31, 2019 and 2020, the taxable temporary differences associated with the investments in subsidiaries for which no deferred tax liabilities have been recognized were NT$27,139,427 thousand and NT$33,474,725 thousand (US$1,192,120 thousand), respectively. i. Income tax assessments The tax returns of the Company and its R.O.C. subsidiaries through 2018 have been examined by the tax authorities.

Earnings Per Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2020
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Earnings Per Share	27. EARNINGS PER SHARE The earnings and weighted average number of ordinary shares outstanding in the computation of earnings per share were as follows: Net profit for the year For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Profit for the year attributable to owners of the Company $ 26,220,721 $ 17,060,591 $ 26,970,580 $ 960,490 Effect of potentially dilutive ordinary shares: Employee share options issued by subsidiaries (418,295 ) (385,865 ) (521,073 ) (18,557 ) Earnings used in the computation of diluted earnings per share $ 25,802,426 $ 16,674,726 $ 26,449,507 $ 941,933 Weighted average number of ordinary shares outstanding For the Year Ended December 31 2018 2019 2020 Weighted average number of ordinary shares in computation of basic earnings per share 4,245,247 4,251,964 4,265,732 Effect of potentially dilutive ordinary shares: From employee share options 5,103 10,232 22,086 (Continued) For the Year Ended December 31 2018 2019 2020 From employees’ compensation 779 570 815 Weighted average number of ordinary shares in computation of diluted earnings per share 4,251,129 4,262,766 4,288,633 For the computation of earnings per ADS, the denominators were the half of the aforementioned weighted average outstanding shares (1 ADS represents 2 ordinary shares) while the numerators held constant. The Group is able to settle the employees’ compensation by cash or shares. The Group assumed that the entire amount of the compensation would be settled in shares and the resulting potential shares were included in the weighted average number of ordinary shares outstanding used in the computation of diluted earnings per share if the effect is dilutive. Such dilutive effect of the potential shares was included in the computation of diluted earnings per share until the board of directors approve the number of shares to be distributed to employees at their meeting in following year.

Share-based Payment Arrangement

Share-based Payment Arrangements	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Share-based Payment Arrangements	28. SHARE-BASED PAYMENT ARRANGEMENTS a. Employee share option plans of the Company In order to attract, retain and reward employees, the Company and its subsidiary, ASE, have their employee share option plans for the Group’s full-time employees. As disclosed in Note 1, the Company assumed ASE’s obligations of outstanding employee share option plans starting from April 30, 2018 and each share option represents the right to purchase 0.5 ordinary share of the Company when exercised. Under the terms of the plan, share options are granted at an exercise price equal to or not less than the closing price of the ordinary shares listed on the TWSE at the issue date. The right of those share options granted under the plan is valid for 10 years, non-transferable and exercisable at certain percentages subsequent to the second anniversary of the grant date. For any subsequent changes in the Company’s capital structure or when cash dividend per ordinary share exceeds 1.5% of the market price per ordinary share, the exercise price is accordingly adjusted. Information about the share option plans that ASE granted for the period from January 1, 2018 through April 29, 2018 was as follows: For the Period from January 1, 2018 through April 29, 2018 Number of Options (In Thousands) Weighted Average Exercise Price Per Share (NT$) Balance, beginning of period 135,961 $ 30.2 Options forfeited (1,692 ) 36.3 Options exercised (20,557 ) 26.0 Options transferred to the Company in accordance with the joint share exchange agreement (113,712 ) 30.9 Balance, end of period - - Information about the share option plans that the Company granted and assumed for the period from April 30, 2018 through December 31, 2018 and for the years ended December 31, 2019 and 2020 were as follows: For the Period from For the Year Ended December 31 December 31, 2018 2019 2020 Weighted Weighted Weighted Average Average Average Number of Exercise Number of Exercise Number of Exercise Options Price Options Price Options Price (In Per Share (In Per Share (In Per Share Thousands) (NT$) Thousands) (NT$) Thousands) (NT$) Balance, beginning of period - $ - 183,814 $ 58.1 170,786 $ 57.0 Options assumed on April 30, 2018 56,856 61.7 - - - - Options granted 131,863 56.4 - - - - Options expired - - - - (1,006 ) 40.8 Options forfeited (1,582 ) 71.5 (4,214 ) 61.8 (3,949 ) 58.0 Options exercised (3,323 ) 43.6 (8,814 ) 48.4 (21,064 ) 49.2 Balance, end of period 183,814 58.1 170,786 57.0 144,767 56.9 Options exercisable, end of period 36,354 58.1 33,822 63.5 67,388 61.4 Fair value of options granted (NT$) $ 16.28-19.12 $ - $ - The weighted average share prices at exercise dates of share options for the period from January 1, 2018 to April 29, 2018, the period from April 30, 2018 to December 31, 2018, and the year ended December 31, 2019 and 2020 were NT$41.0, NT$68.5, NT$69.3 and NT$68.5 (US$2.4), respectively. Information about the outstanding share options that the Company granted and assumed at each balance sheet date was as follows: Range of Exercise Price Per Share (NT$) Weighted Average Remaining Contractual Life (Years) December 31, 2019 ASE 4 th $ 40.8-45.2 0.5 ASE 5 th 73.0 5.7 The Company 1 st 54.4 8.9 December 31, 2020 ASE 4 th 45.2 0.3 ASE 5 th 73.0 4.7 The Company 1 st 52.9 7.9 b. Employee share option plans of subsidiaries USIE The terms of the plans issued by USIE were the same with those option plans previously granted by ASE. Information about share options was as follows: For the Year Ended December 31 2018 2019 2020 Weighted Weighted Weighted Number of Average Exercise Number of Average Exercise Number of Average Exercise Options Price Options Price Options Price (In Per Share (In Per Share (In Per Share Thousands) (US$) Thousands) (US$) Thousands) (US$) Balance at January 1 25,556 $ 2.2 16,711 $ 2.1 8,349 $ 2.3 Options forfeited - - - - (7 ) 2.9 Options exercised (8,845 ) 2.2 (8,362 ) 2.0 (8,342 ) 2.3 Balance at December 31 16,711 2.1 8,349 2.3 - - Options exercisable, end of year 16,711 2.1 8,349 2.3 - - Information about USIE’s outstanding share options at each balance sheet date was as follows: Range of Exercise Price Per Share (US$) Weighted Average Remaining Contractual Life (Years) December 31, 2019 1 st $ 1.5 1.0 3 rd 2.9 1.4 In 2018, 2019 and 2020, the Group’s shareholdings in USIE decreased because USIE’s share options were exercised. The transaction was accounted for as an equity transaction since the Group did not cease to have control over USIE and, as a result, capital surplus was decreased by NT$1,239,456 thousand, NT$981,078 thousand and NT$1,120,111 thousand (US$39,890 thousand) for the years ended December 31, 2018, 2019 and 2020, respectively. USISH Under the share option plan issued in 2015 (“2015 share options”), each unit represents the right to purchase one ordinary share of USISH when exercised. The options are valid for 10 years, non-transferable and exercisable at certain percentages subsequent to the second anniversary of the grant date incorporated with certain performance conditions. For any subsequent changes in USISH’s capital structure, the exercise price is accordingly adjusted. In November 2019, USISH adopted the first share option plan (“2019 share options”) and granted 17,167 thousand share options to its employees. Each unit represents the right to purchase one ordinary share of USISH when exercised. The options are valid for 3.0 years, 4.0 years and 5.0 years, respectively, and are exercisable at certain percentages within 12 months subsequent to the second, the third and the fourth anniversary of the grant date under the satisfaction of certain performance conditions within each respective vesting period. In the event that USISH increases share capital by capital surplus or by cash, or distributes share dividends or cash dividends, the exercisable share option units and the exercise price are accordingly adjusted. In September 2020, USISH adopted the second share option plan (“2020 share options”) and granted 1,140 thousand share options to its employees. The conditions of issued 2020 share options are the same as 2019 share options plan, except that the options are valid for 2.2 years, 3.2 years and 4.2 years, respectively, and with each respective vesting period of 1.2 years, 2.2 years and 3.2 years. Information about share options was as follows: For the Year Ended December 31 2018 2019 2020 Number of Exercise Number of Exercise Number of Exercise Options Price Options Price Options Price (In Per Share (In Per Share (In Per Share Thousands) (RMB) Thousands) (RMB) Thousands) (RMB) Balance at January 1 22,341 $ 15.5 21,537 $ 15.5 35,077 $ 14.5 Options granted - - 17,167 13.3 1,140 21.7 Options forfeited (804) 15.5 (463 ) 15.4 (636 ) 14.0 Options exercised - - (3,164 ) 15.5 (4,315 ) 15.5 Balance at December 31 21,537 15.5 35,077 14.5 31,266 14.6 Options exercisable, end of year 12,884 15.5 13,694 15.5 13,416 15.5 Fair value of options granted (RMB) - $ 6.27-8.35 $ 7.03-8.93 Information about USISH’s outstanding share options at each balance sheet date was as follows: Range of Exercise Price Per Share (RMB) Remaining Contractual Life (Years) December 31, 2019 2015 share options $ 15.5 5.9 2019 share options 13.3 4.9 December 31, 2020 2015 share options 15.5 4.9 2019 share options 13.3 3.9 2020 share options 21.7 3.9 c. Employee restricted share plans of subsidiaries In November 2019, USISH adopted the first restricted share plan (“2019 restricted shares”) and granted 6,156 thousand ordinary shares to its directors (excluding independent directors), supervisors and employees. In April 2020, the board of directors further resolved to grant 6,403 thousand ordinary shares instead, while other terms remain constant. The plan was of 3 phases starting from 2019 and each phase lasts for 1 year with a valid period of 4.5 years, 3.5 years and 2.5 years, respectively. Upon satisfaction of certain performance conditions in each phase, participants are entitled to subscribe a certain percentage of the total USISH’s ordinary shares issued under the plan with a lock-up period of 1 year. The valid period may be early terminated or extended prior to one month of the expiration date depending on the conditions of ordinary shares granted. In the event that USISH increases share capital by capital surplus or by cash, or distributes share dividends or cash dividends, the exercise price is accordingly adjusted. In September 2020, USISH adopted the second restricted share plan (“2020 restricted shares”) and granted 425 thousand ordinary shares to its employees. The conditions of issued 2020 restricted shares are the same as 2019 restricted shares plan, except that the restricted shares are valid for 2 years and the ordinary shares that USISH would issue to participants for free are with a lock-up period of 1.3 year. Information about restricted shares was as follows: For the Year Ended December 31 2019 2020 Number of Exercise Number of Exercise Options Price Options Price (In Per Share (In Per Share Thousands) (RMB) Thousands) (RMB) Balance at January 1 - $ - 6,156 $ 13.3 Options granted 6,156 13.3 672 4.9 Options exercised - - (1,281 ) 13.2 Balance at December 31 6,156 13.3 5,547 12.2 Options exercisable, end of year - - - - Fair value of options granted (RMB) $ 13.47 $ 18.55 Information about USISH’s outstanding restricted shares at each balance sheet date was as follows: Range of Exercise Price Per Share (RMB) Remaining Contractual Life (Years) December 31, 2019 2019 restricted shares 13.3 4.3 December 31, 2020 2019 restricted shares 13.2 3.3 2020 restricted shares - 1.7 The Group’s shareholdings in USISH decreased because the abovementioned share option plans and restricted share plan were exercised in 2019 and 2020. The transaction was accounted for as an equity transaction since the Group did not cease to have control over USISH and, as a result, capital surplus increased by NT$105,785 thousand in 2019 and NT$1,010,219 thousand (US$35,976 thousand) in 2020. d. Fair value information For the fair values at the grant date of USISH’s 2019 and 2020 plans, the share options plans were measured by using the trinomial tree model, while the restricted shares plans were measured by using the Black-Scholes Option Pricing Model incorporating the effect of the lock-up period. The inputs to the models were as follows: Share option plan 2019 share options plan 2020 share options plan Share price at the grant date RMB15.84 per share RMB21.55 per share Exercise price RMB13.34 per share RMB21.65 per share Expected volatility (%) 45.07-51.80 48.14-53.57 Expected lives (years) 3-5 2.2-4.2 Expected dividend yield - - Risk free interest rate (%) 2.80-2.97 2.80-2.99 Restricted share plan 2019 restricted shares plan 2019 restricted shares plan amended in 2020 2020 restricted shares plan Share price at the grant date RMB16.30 per share RMB16.60 per share RMB24.30 per share Exercise price RMB13.34 per share RMB13.34 per share (Note) Expected volatility (%) 47.77 57.21 56.97 Lock-up periods (years) 1 1 1.3 Expected dividend yield - - - Risk free interest rate (%) 2.70 1.55 2.63 Note: The restricted sha r Expected volatilities we r For the years ended December 31, 2018, 2019 and 2020, employee benefits expense recognized on the aforementioned employee share option plans and the restricted share plans were NT$215,648 thousand, NT$871,699 thousand and NT$955,575 thousand (US$34,030 thousand), respectively.

Business Combinations

Business Combinations	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Business Combinations	29. BUSINESS COMBINATIONS a. Subsidiaries acquired Principal Activity Date of Acquisition Proportion of Voting Equity Interests Acquired (%) Consideration Transferred NT$ US$ (Note 4) SPIL Engaged in the assembly, testing and turnkey services of integrated circuits April 30, 2018 100.00 $ 168,440,585 AMPI Engaged in the April 30, 2019 50.97 $ 250,000 ASEEE Engaged in the production of embedded substrate April 26, 2019 51.00 - Principal Activity Date of Acquisition Proportion of Voting Equity Interests Acquired (%) Consideration Transferred NT$ US$ (Note 4) USIPL Engaged in the design and manufacturing of electronic components and new electronic applications October 31, 2019 60.00 $ 313,057 FAFG Holding company and the group engaged in the design and manufacturing of electronic components December 1, 2020 100.00 $ 12,829,372 $ 456,886 b. Consideration Transferred SPIL AMPI ASEEE USIPL FAFG NT$ NT$ NT$ NT$ NT$ US$ (Note 4) Cash $ 168,440,585 $ 250,000 $ - $ 313,057 $ 10,800,558 $ 384,635 Equity instrument issued - - - - 1,734,570 61,772 Contingent consideration arrangement - - - - 294,244 10,479 Fair value of identifiable net assets acquired $ 168,440,585 $ 250,000 $ - $ 313,057 $ 12,829,372 $ 456,886 In April, 2018, the Company acquired all issued and outstanding ordinary shares of SPIL in accordance with the joint share exchange agreement and had the control over SPIL. The investment in SPIL originally accounted for using the equity method was remeasured to the fair value at the acquisition date and the Group recognized a remeasurement gain of NT$7,421,408 thousand for the year ended December 31, 2018 (Note 25). In April 2019, the Group’s subsidiary, ASE Test, Inc., subscribed for 100,000 thousand ordinary shares of AMPI from its private placement with NT$250,000 thousand in cash. The percentage of the Group’s ownership in AMPI then increased to 50.97% and, therefore, the Group obtained control over AMPI. The investment in ordinary shares of AMPI originally accounted for using the equity method was remeasured to the fair value at the acquisition date and the Group recognized remeasurement gain of NT$243,057 thousand under the line item of other gains and losses (Note 25). In April 2019, ASE entered into a memorandum of understanding with TDK Corporation (“TDK”) in relation to ASEEE that was incorporated by a joint venture agreement entered into by the Group and TDK. In addition to a reduction of one legal representative director of TDK, which resulted in that the Group obtained control over ASEEE starting from April 2019 and the investments in ASEEE originally accounted for using the equity method was remeasured to its fair value at the acquisition date with a remeasurement gain of NT$76,655 thousand under the line item of other gains and losses (Note 25), the memorandum of understanding set out that, after ASEEE offset its accumulated deficits against its capital in an amount of NT$1,147,595 thousand, ASE subscribed all of 150,000 thousand ordinary shares newly issued by ASEEE through its capital increase by cash in an amount of NT$1,500,000 thousand in May 2019 and then repurchased all of ASEEE’s ordinary shares held by TDK in an amount of US$6,000 thousand in July 2019. As a result, the Group eventually held 100% of ownership in ASEEE (Note 31). Furthermore, ASE merged ASEEE in February 2020. In October 2019, the Group’s subsidiary, Universal Global Electronics Co., Ltd., acquired 60% shareholdings of USIPL with a total consideration based on independent professional appraisal reports. In December 2020, the Group’s subsidiary, USIFR, paid NT$10,800,558 thousand (equivalent to US$368,753 thousand) and the Group’s subsidiary, USISH, issued its 25,940 thousand new ordinary shares to acquire 100% shareholdings of FAFG. In addition, according to the share purchase agreement, USIFR is obliged to pay an earn-out amount up to US$42,805 thousand in 2023 if FAFG’s net profit in 2021 and 2022 reaches the predetermined target. In December 2020, USIFR deposited NT$294,244 thousand (equivalent to US$10,122 thousand) in advance to trust account. The consideration transferred was tentative as of December 31, 2020 because the fair values of the ordinary shares newly issued by USISH and the contingent consideration arrangement for the earn-out were still being determined. c. Assets acquired and liabilities assumed at the date of acquisition SPIL AMPI ASEEE USIPL FAFG NT$ NT$ NT$ NT$ NT$ US$ (Note 4) Assets Cash and cash equivalents $ 20,088,970 $ 349,496 $ 23,197 $ 108,718 $ 2,349,164 $ 83,660 Trade and other receivables 15,840,649 371,144 5,732 58,713 4,434,296 157,917 Inventories 5,693,644 403,887 11,033 229 4,763,237 169,631 Property, plant and equipment 81,985,622 683,207 1,361,572 525,048 1,730,783 61,637 Intangible assets 31,354,386 128,900 290,757 11,704 642,838 22,893 Others 24,945,922 237,766 317,888 99,112 1,798,564 64,051 Liabilities Trade and other payables (19,755,598 ) (224,295 ) (133,278 ) (217,887 ) (4,575,720 ) (162,953 ) Borrowings and bonds payables (24,157,174 ) (951,519 ) (1,371,395 ) (190,737 ) (356,417 ) (12,693 ) Others (3,963,201 ) (148,723 ) (290,273 ) (63,708 ) (2,588,277 ) (92,175 ) Fair value of identifiable net assets acquired $ 132,033,220 $ 849,863 $ 215,233 $ 331,192 $ 8,198,468 $ 291,968 A call option on the remaining 40% non-controlling interests of USIPL was stipulated in the equity transfer agreement. The Group recognized the call option under the line item of financial assets at FVTPL (Note 7) and exercised it in June 2020 (Note 31). The initial accounting for the acquisition of FAFG was incomplete as of December 31, 2020 and the Group reported in the financial statements provisional amounts for assets acquired and liabilities assumed. d. Non-controlling interest Non-controlling interests of SPIL were measured at fair value at the acquisition date by using market approach based on the valuation multiples of comparable companies and the discount rate for lack of marketability. The significant unobservable inputs is the discount rate for lack of marketability of 25%. Non-controlling interests of AMPI and ASEEE were measured at their proportionate share of the fair value of AMPI’s and ASEEE’s identifiable net assets, respectively. Non-controlling interests of USIPL were measured at fair value at the acquisition date by using market approach incorporating transaction prices of comparable companies and the discount rate for lack of control. The significant unobservable inputs is the discount rate for lack of control of 31%. Non-controlling interests of FAFG were measured at its proportionate share of the fair value of FAFG’s identifiable net assets. As aforementioned, such non-controlling interests measurements were tentative as of December 31, 2020. e. Goodwill recognized on acquisitions SPIL AMPI ASEEE USIPL FAFG NT$ NT$ NT$ NT$ NT$ US$ (Note 4) Consideration transferred $ 168,440,585 $ 250,000 $ - $ 313,057 $ 12,829,372 $ 456,887 Add: Fair value of investments previously owned - 315,925 117,609 - - - Add: Non-controlling interests 3,582,866 416,716 105,464 142,494 (5,635 ) (201 ) Less: Fair value of identifiable net assets acquired (132,033,220 ) (849,863 ) (215,233 ) (331,192 ) (8,198,468 ) (291,968 ) Goodwill recognized on acquisition $ 39,990,231 $ 132,778 $ 7,840 $ 124,359 $ 4,625,269 $ 164,718 The goodwill from acquisitions mainly represents the control premium. In addition, the consideration paid for acquisitions effectively included amounts attributed to the benefits of expected synergies, such as revenue growth and future market expansions. These benefits are not recognized separately from goodwill because they do not meet the recognition criteria for identifiable intangible assets. The goodwill recognized on acquisitions is not expected to be deductible for tax purpose. As of December 31, 2020, the Group has not completed the identification of the difference between the cost of the investment and the Group’s share of the net fair value of FAFG’s identifiable assets and liabilities and, as a result, the difference was recognized as goodwill provisionally. The group continuously review the abovementioned items during the measuring period. If there is any new information obtained within one year from the acquisition date about the facts and circumstances that existed as of the acquisition date, for which the abovementioned provisional amounts recognized at the acquisition date should be adjusted or additional provision should be recognized, the accounting for the business combination will be retrospectively adjusted. f. Net cash outflow (inflow) on acquisition of subsidiaries SPIL AMPI ASEEE USIPL FAFG NT$ NT$ NT$ NT$ NT$ US$ (Note 4) Consideration paid in cash $ 168,440,585 $ 250,000 $ - $ 313,057 $ 11,094,802 $ 395,114 Less: Payable for consideration representing the ordinary shares originally held by ASE (53,109,760 ) - - - - - Less: Cash and cash equivalent acquired (20,088,970 ) (349,496 ) (23,197 ) (108,718 ) (2,349,164 ) (83,660 ) Net cash outflow (inflow) on acquisition of subsidiaries $ 95,241,855 $ (99,496 ) $ (23,197 ) $ 204,339 $ 8,745,638 $ 311,454 g. Impact of acquisitions on the results of the Group The results of operations since the acquisition date were included in the consolidated statements of comprehensive income and were as follows: SPIL (For the Period from April 30, 2018 through December 31, 2018) AMPI (For the Period from April 30, 2019 through December 31, 2019) ASEEE (For the Period from April 26, 2019 through December 31, 2019) USIPL (For the Period from October 31, 2019 through December 31, 2019) FAFG (For the Period from December 1, 2020 through December 31, 2020) NT$ NT$ NT$ NT$ NT$ US$ (Note 4) Operating revenue $ 61,247,727 $ 704,243 $ (1,159 ) $ 39,080 $ 2,043,440 $ 72,772 Net profit (loss) $ 7,627,382 $ (217,163 ) $ (469,598 ) $ (11,995 ) $ 91,179 $ 3,247 Had SPIL, AMPI, ASEEE, USIPL and FAFG business combinations been in effect at the beginning of each annual reporting period and the investments originally accounted for using the equity method been remeasured to their fair value as of January 1 of each respective annual reporting period, the Group’s operating revenues and profit for the year would have been NT$397,261,461 thousand and NT$25,687,447 thousand for the year ended December 31, 2018, respectively, NT$413,782,708 thousand and NT$18,030,506 thousand for the year ended December 31, 2019, respectively, and NT$497,146,285 thousand (US$17,704,640 thousand) and NT$29,707,746 thousand (US$1,057,968 thousand) for the year ended December 31, 2020, respectively. This pro-forma information is for illustrative purposes only and is not necessarily an indication of the operating revenue and results of operations of the Group that actually would have been achieved had the acquisition been completed at the beginning of each annual reporting period, nor is it intended to be a projection of future results. In determining the pro-forma operating revenue and profit for the period had each subsidiary been acquired at the beginning of each respective annual reporting period, the Group has calculated the depreciation of property, plant and equipment and the amortization of intangible assets acquired on the basis of the fair values at the initial accounting for the business combination rather than the carrying amounts recognized in the respective pre-acquisition financial statements.

Disposal of Subsidiaries

Disposal of Subsidiaries	12 Months Ended
	Dec. 31, 2020
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Disposal of Subsidiaries	30. DISPOSAL OF SUBSIDIARIES The board of directors of the Group’s subsidiary, SPIL (Cayman) Holding Limited, resolved in September 2020 to dispose its 100% shareholdings in SF to Shenzhen Hiwin System Limited with a consideration of RMB966,000 thousand. The disposal was completed in October 2020 and the control over SF passed to the acquirer. a. Analysis of assets and liabilities on the date control was lost NT$ US$ (Note 4) Current Assets Cash and cash equivalent $ 200,347 $ 7,135 Trade receivables, net 318,425 11,340 Inventories 239,865 8,542 Other current assets 111,913 3,985 Non-Current Assets Property, plant and equipment 7,546,413 268,747 Right-of-use assets 812,861 28,948 Deferred tax assets 298,217 10,620 Other non-current assets 43,482 1,548 Current Liabilities Trade and other payables (1,739,330 ) (61,942 ) Current portion of long-term borrowings (1,746,000 ) (62,179 ) Other current liabilities (24,564 ) (875 ) NT$ US$ (Note 4) Non-Current Liabilities Long-term borrowings (2,947,682 ) (104,974 ) Deferred tax liabilities (796 ) (28 ) Net assets disposed of $ 3,113,151 $ 110,867 b. Gain on disposal of subsidiarie s NT$ US$ (Note 4) Total consideration (paid in cash) $ 4,078,844 $ 145,258 Net assets disposed of (3,113,151 ) (110,867 ) Reclassification of accumulated exchange difference from equity to profit or loss due to the loss of control over SF (162,940 ) (5,803 ) Gain on disposal of SF $ 802,753 $ 28,588

Equity Transaction with Non-con

Equity Transaction with Non-controlling Interests	12 Months Ended
	Dec. 31, 2020
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Equity Transaction with Non-controlling Interests	31. EQUITY TRANSACTION WITH NON-CONTROLLING INTERESTS a. USIE In July 2019, the shareholders’ meeting of USIE resolved to repurchase its own outstanding 7,378 thousand ordinary shares at US$14.30 per share, and, as a result, the Group’s shareholdings in USIE increased from 95.42% to 98.72%. The transaction was accounted for as an equity transaction since the transaction did not change the Group’s control over USIE and the Group capital surplus decreased by NT$1,625,448 thousand in 2019. In July 2019, the board of directors of USIE resolved July 23, 2019 was the record date for capital reduction and then the repurchased ordinary shares were subsequently cancelled. In September 2020, the shareholders’ meeting of USIE resolved to repurchase its own outstanding 10,308 thousand ordinary shares at US$19.47 per share, and, as a result, the Group’s shareholdings in USIE increased from 95% to 99.62%. The transaction was accounted for as an equity transaction since the transaction did not change the Group’s control over USIE and the Group decreased capital surplus and retained earnings by NT$780,533 thousand (US$27,797 thousand) and NT$2,760,175 thousand (US$98,297 thousand), respectively, in 2020. In September 2020, the board of directors of USIE resolved September 15, 2020 was the record date for capital reduction and then the repurchased ordinary shares were subsequently cancelled. b. ASEN and SZ In July 2019, ASE’s board of directors resolved to acquire 30% shareholdings of ASEN from Beijing Unis Capital Management Co., Ltd. at US$97,748 thousand by its subsidiary, J&R Holding. In addition, in July 2019, SPIL’s board of directors also resolved to acquire 30% shareholdings of SZ from Tibet Zixi Electronic Technology Co., Ltd. at US$162,870 thousand by its subsidiary, SPIL (Cayman) Holding Limited. The aforementioned transactions will result the Group’s shareholdings of ASEN and SZ both to increase from 70% to 100% and, therefore, both transactions will be accounted for as an equity transaction since the Group will not cease to have control over the subsidiaries. The Group recognized a decrease in capital surplus by NT$2,650,950 thousand in 2019. c. USIPL In May 2020, the board of directors of Universal Global Electronics Co., Ltd. resolved to acquire 40% shareholdings of USIPL from Chung Hong Electronics (Suzhou) Co., Ltd. at RMB24,500 thousand. The aforementioned transaction resulted the Group’s shareholdings in USIPL to increase from 60% to 100%, and such transactions were accounted for as an equity transaction since the transaction did not change the Group’s control over USIPL. The Group recognized a decrease in capital surplus by NT$13,502 thousand (US$481 thousand) in 2020. d. Others In July 2018, UGTW’s board of directors approved to acquire the outstanding ordinary shares of USI at NT$18 per ordinary shares. In the first quarter of 2019, UGTW completed the acquisition and recognized an increase in capital surplus by NT$142 thousand. USISH repurchased its own 13,037 thousand outstanding ordinary shares during year ended December 31, 2019 and, as a result, the Group’s shareholdings of USISH increased from 74.6% to 77.7%. The transaction was accounted for as an equity transaction since the Group did not cease to have control over USISH and capital surplus was decreased by NT$334,719 thousand. As disclosed in Note 29, ASE purchased ASEEE’s ordinary shares through its capital increase in May 2019 and then repurchased all of ASEEE’s ordinary shares held by TDK in July 2019. As a result, the Group eventually held 100% of ownership in ASEEE and capital surplus was decreased by NT$128,805 thousand.

Cash Flows Information

Cash Flows Information	12 Months Ended
	Dec. 31, 2020
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Cash Flows Information	32. CASH FLOWS INFORMATION a. Non-cash investing activities In addition to other notes, the Group entered into the following investing activities which include both cash and non-cash items for the years ended December 31, 2018, 2019 and 2020: For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Payments for property, plant and equipment Purchase of property, plant and equipment $ 39,092,238 $ 63,073,887 $ 59,024,201 $ 2,102,001 Increase in other non-current assets 402,255 68,560 78,291 2,788 (Continued) For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Decrease (increase) in other payables $ 1,942,259 $ (6,254,579 ) $ 3,029,162 $ 107,876 Capitalized borrowing costs (50,309 ) (77,715 ) (54,208 ) (1,930 ) $ 41,386,443 $ 56,810,153 $ 62,077,446 $ 2,210,735 Proceeds from disposal of property, plant and equipment Consideration from disposal of property, plant and equipment $ 1,133,435 $ 441,444 $ 5,184,925 $ 184,648 Decrease (increase) in other receivables (5,791 ) 7,495 (735,812 ) (26,204 ) $ 1,127,644 $ 448,939 $ 4,449,113 $ 158,444 Payments for investment properties Purchase of investment properties $ 125,853 $ 2,532 $ - $ - Capitalized borrowing costs (89 ) - - - $ 125,764 $ 2,532 $ - $ - Payments for other intangible assets Purchase of other intangible assets $ 537,659 $ 1,350,908 $ 982,655 $ 34,995 Decrease in other payables 40,106 60,160 - - $ 577,765 $ 1,411,068 $ 982,655 $ 34,995 (Concluded) b. Changes in liabilities arising from financing activities For the year ended December 31, 2018 Short-term Borrowings Bonds Payable Long-term Borrowings Total NT$ NT$ NT$ NT$ Balance at January 1, 2018 $ 17,962,471 $ 23,142,780 $ 35,406,628 $ 76,511,879 Net financing cash flows 22,327,813 (6,185,600 ) 85,510,959 101,653,172 Non-cash changes Acquisition through business combinations 3,619,858 4,457,191 16,080,125 24,157,174 Bonds conversion - (4,457,191 ) - (4,457,191 ) Reclassification for the application of IFRS 9 (1,301,994 ) - - (1,301,994 ) Amortization of issuance cost - 28,756 188,217 216,973 Effects of foreign currency exchange 655,321 - 712,400 1,367,721 Balance at December 31, 2018 $ 43,263,469 $ 16,985,936 $ 137,898,329 $ 198,147,734 For the year ended December 31, 2019 Short-term Borrowings (including financial liabilities for hedging) Bonds Payable Long-term Borrowings Lease Liabilities Total NT$ NT$ NT$ NT$ NT$ Balance at January 1, 2019 $ 47,163,103 $ 16,985,936 $ 137,898,329 $ 6,084,729 $ 208,132,097 Net financing cash flows (4,683,142 ) 19,279,033 1,144,731 (636,556 ) 15,104,066 Interest under operating activities - - - 1,766 1,766 Non-cash changes Lease liabilities - - - 536,216 536,216 Acquisition through business combinations (Note 29) 656,820 245,664 1,523,968 81,649 2,508,101 Amortization of issuance cost - 11,522 189,151 - 200,673 Lease modifications - - - (239,321 ) (239,321 ) Short-term borrowings transferred to long-term borrowings (1,499,000 ) - 1,499,000 - - Effects of foreign currency exchange (1,065,452 ) - (1,176,581 ) (19,559 ) (2,261,592 ) Balance at December 31, 2019 $ 40,572,329 $ 36,522,155 $ 141,078,598 $ 5,808,924 $ 223,982,006 For the year ended December 31, 2020 Short-term Borrowings (including financial liabilities for hedging) Bonds Payable Long-term Borrowings (including financial liabilities for hedging) Lease Liabilities Total NT$ NT$ NT$ NT$ NT$ Balance at January 1, 2020 $ 40,572,329 $ 36,522,155 $ 141,078,598 $ 5,808,924 $ 223,982,006 Net financing cash flows (1,502,323 ) 19,717,149 (26,500,139 ) (844,357 ) (9,129,670 ) Interest under operating activities - - - 111 111 Rent expense under operating activities - - - (7,729 ) (7,729 ) Non-cash changes Lease liabilities - - - 584,642 584,642 Amortization of issuance cost - 14,250 156,982 - 171,232 Lease modifications - - - (289,687 ) (289,687 ) Short-term borrowings transferred to long-term borrowings (3,850,000 ) - 3,850,000 - - Adjustments for government subsidy - - 41,650 - 41,650 Acquisition of subsidiaries (Note 29) 356,417 - - 633,606 990,023 Disposal of subsidiaries (Note 30) - - (4,693,682 ) (670 ) (4,694,352 ) Effects of foreign currency exchange (978,565 ) - (1,542,685 ) (9,010 ) (2,530,260 ) Balance at December 31, 2020 $ 34,597,858 $ 56,253,554 $ 112,390,724 $ 5,875,830 $ 209,117,966 Short-term Borrowings (including financial liabilities for hedging) Bonds Payable Long-term Borrowings (including financial liabilities for hedging) Lease Liabilities Total US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) Balance at January 1, 2020 $ 1,444,883 $ 1,300,647 $ 5,024,168 $ 206,871 $ 7,976,569 Net financing cash flows (53,502 ) 702,178 (943,737 ) (30,070 ) (325,131 ) Interest under operating activities - - - 4 4 Rent expense under operating activities - - - (275 ) (275 ) Non-cash changes Lease liabilities - - - 20,821 20,821 Amortization of issuance cost - 507 5,591 - 6,098 Lease modifications - - - (10,316 ) (10,316 ) (Continued) Short-term Borrowings (including financial liabilities for hedging) Bonds Payable Long-term Borrowings (including financial liabilities for hedging) Lease Liabilities Total US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) Short-term borrowings transferred to long-term borrowings (137,108 ) - 137,108 - - Adjustments for government subsidy - - 1,483 - 1,483 Acquisition of subsidiaries (Note 29) 12,693 - - 22,564 35,257 Disposal of subsidiaries (Note 30) - - (167,154 ) (24 ) (167,178 ) Effects of foreign currency exchange (34,849 ) - (54,939 ) (322 ) (90,110 ) Balance at December 31, 2020 $ 1,232,117 $ 2,003,332 $ 4,002,520 $ 209,253 $ 7,447,222 (Concluded)

Capital Management

Capital Management	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Capital Management	33. CAPITAL MANAGEMENT The capital structure of the Group consists of debt and equity. The Group manages its capital to ensure that entities in the Group will be able to continue as going concerns while maximizing the return to shareholders through the optimization of the debt and equity balance. Key management personnel of the Group periodically reviews the cost of capital and the risks associated with each class of capital. In order to balance the overall capital structure, the Group may adjust the amount of dividends paid to shareholders, the number of new shares issued or repurchased, and the amount of new debt issued or existing debt redeemed. The Group is not subject to any externally imposed capital requirements except those discussed in Note 20.

Financial Instruments

Financial Instruments	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Financial Instruments	34. FINANCIAL INSTRUMENTS a. Fair value of financial instruments that are not measured at fair value 1) Fair value of financial instruments not measured at fair value but for which fair value is disclosed Except bonds payable measured at amortized cost, the management considered that the carrying amounts of financial assets and financial liabilities not measured at fair value approximate their fair values. The carrying amounts and fair value of bonds payable as of December 31, 2019 and 2020 were as follows: Carrying Amount Fair Value NT$ US$ (Note 4) NT$ US$ (Note 4) December 31, 2019 $ 36,522,155 $ 36,766,117 December 31, 2020 56,253,554 $ 2,003,332 56,448,769 $ 2,010,284 2) Fair value hierarchy The aforementioned fair value hierarchy of bonds payable was Level 3 which was determined based on discounted cash flow analysis with the applicable yield curve for the duration. The significant unobservable inputs is discount rates that reflected the credit risk. b. Fair value of financial instruments that are measured at fair value on a recurring basis 1) Fair value hierarchy Level 1 Level 2 Level 3 Total NT$ NT$ NT$ NT$ December 31, 2019 Financial assets at FVTPL Derivative financial assets Forward exchange contracts $ - $ 104,308 $ - $ 104,308 Swap contracts - 56,561 - 56,561 Call option - - 24,556 24,556 Non-derivative financial assets Quoted ordinary shares 3,460,123 - - 3,460,123 Open-end mutual funds 662,290 - - 662,290 Private-placement funds - - 603,718 603,718 Unquoted preferred shares - - 377,440 377,440 $ 4,122,413 $ 160,869 $ 1,005,714 $ 5,288,996 Financial assets at FVTOCI Investments in equity instruments Unquoted ordinary shares $ - $ - $ 565,028 $ 565,028 Unquoted preferred shares - - 158,718 158,718 Limited partnership - - 32,157 32,157 Investments in debt instruments Unsecured subordinate corporate bonds - - 1,014,872 1,014,872 Trade receivables, net - - 2,029,690 2,029,690 $ - $ - $ 3,800,465 $ 3,800,465 Financial liabilities at FVTPL Derivative financial liabilities Swap contracts $ - $ 862,581 $ - $ 862,581 Forward exchange contracts - 110,990 - 110,990 $ - $ 973,571 $ - $ 973,571 Level 1 Level 2 Level 3 Total NT$ US$ (Note 4) NT$ US$ (Note 4) NT$ US$ (Note 4) NT$ US$ (Note 4) December 31, 2020 Financial assets at FVTPL Derivative financial assets Forward exchange contracts $ - $ - $ 122,511 $ 4,363 $ - $ - $ 122,511 $ 4,363 Swap contracts - - 99,312 3,537 - - 99,312 3,537 Non-derivative financial assets Quoted ordinary shares 4,064,438 144,745 - - - - 4,064,438 144,745 Private-placement funds - - - - 1,124,754 40,055 1,124,754 40,055 Unquoted preferred shares - - - - 385,440 13,726 385,440 13,726 Open-end mutual funds 339,338 12,085 - - - - 339,338 12,085 $ 4,403,776 $ 156,830 $ 221,823 $ 7,900 $ 1,510,194 $ 53,781 $ 6,135,793 $ 218,511 Financial assets at FVTOCI Investments in equity instruments Unquoted ordinary shares $ - $ - $ - $ - $ 567,377 $ 20,206 $ 567,377 $ 20,206 Unquoted preferred shares - - - - 151,329 5,389 151,329 5,389 Limited partnership - - - - 9,692 345 9,692 345 Investments in debt instruments Unsecured subordinate corporate bonds - - - - 1,012,736 36,066 1,012,736 36,066 Trade receivables, net - - - - 626,413 22,308 626,413 22,308 $ - $ - $ - $ - $ 2,367,547 $ 84,314 $ 2,367,547 $ 84,314 Financial liabilities at FVTPL Derivative financial liabilities Swap contracts $ - $ - $ 1,448,972 $ 51,602 $ - $ - $ 1,448,972 $ 51,602 Target redemption forward contracts - - 79,216 2,821 - - 79,216 2,821 Forward exchange contracts - - 9,020 321 - - 9,020 321 $ - $ - $ 1,537,208 $ 54,744 $ - $ - $ 1,537,208 $ 54,744 For the financial assets and liabilities that were measured at fair value on a recurring basis, there were no transfers between Level 1 and Level 2 of the fair value hierarchy during the years ended December 31, 2019 and 2020. 2) Reconciliation of Level 3 fair value measurements of financial assets For the year ended December 31, 2019 Financial Assets at FVTPL Financial Assets at FVTOCI Financial Assets Equity Instruments Equity Instruments Debt Instruments Total NT$ NT$ NT$ NT$ Balance at January 1 $ 475,123 $ 580,399 $ 1,016,924 $ 2,072,446 Recognized in profit or loss 3,431 - - 3,431 Recognized in other comprehensive income 　Included in unrealized losses on financial assets at FVTOCI - (216,121 ) (2,052 ) (218,173 ) 　Effects of foreign currency exchange (14,368 ) (5,695 ) - (20,063 ) Net increase in trade receivables - - 3,171,205 3,171,205 Trade receivables factoring - - (1,141,515 ) (1,141,515 ) Purchases 541,528 409,985 - 951,513 Disposals - (12,665 ) - (12,665 ) Balance at December 31 $ 1,005,714 $ 755,903 $ 3,044,562 $ 4,806,179 For the year ended December 31, 2020 Financial Assets at FVTPL Financial Assets at FVTOCI Financial Assets Equity Instruments Debt Instruments Equity Instruments Debt Instruments Total NT$ NT$ NT$ NT$ NT$ Balance at January 1 $ 1,005,714 $ - $ 755,903 $ 3,044,562 $ 4,806,179 Recognized in profit or loss (17,941 ) - - - (17,941 ) Recognized in other comprehensive income Includevd in unrealized losses on financial assets at FVTOCI - - (149,856 ) (2,136 ) (151,992 ) Effects of foreign currency exchange (15,455 ) - (15,562 ) - (31,017 ) Net increase in trade receivables - 370,110 - 5,635,706 6,005,816 Trade receivables factoring - (370,110 ) - (7,038,983 ) (7,409,093 ) Purchases 893,234 - 259,168 - 1,152,402 Disposals (329,370 ) - (121,255 ) - (450,625 ) Exercise of call option (25,988 ) - - - (25,988 ) Balance at December 31 $ 1,510,194 $ - $ 728,398 $ 1,639,149 $ 3,877,741 Financial Assets at FVTPL Financial Assets at FVTOCI Financial Assets Equity Instruments Debt Instruments Equity Instruments Debt Instruments Total US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) Balance at January 1 $ 35,816 $ - $ 26,920 $ 108,424 $ 171,160 Recognized in profit or loss (639 ) - - - (639 ) Recognized in other comprehensive income Included in unrealized losses on financial assets at FVTOCI - - (5,337 ) (76 ) (5,413 ) Effects of foreign currency exchange (550 ) - (555 ) - (1,105 ) Net increase in trade receivables - 13,181 - 200,702 213,883 Trade receivables factoring - (13,181 ) - (250,676 ) (263,857 ) Purchases 31,810 - 9,230 - 41,040 Disposals (11,730 ) - (4,318 ) - (16,048 ) Exercise of call option (926 ) - - - (926 ) Balance at December 31 $ 53,781 $ - $ 25,940 $ 58,374 $ 138,095 3) Valuation techniques and assumptions applied for the purpose of measuring fair value a) Valuation techniques Financial Instruments Valuation Techniques and Inputs Derivatives - swap contracts and forward exchange contracts Discounted cash flows - Future cash flows are estimated based on observable forward exchange rates at balance sheet dates and contract forward exchange rates, discounted at rates that reflected the credit risk of various counterparties. Target redemption forward contracts Valuation based on the spot exchange rate on the valuation date, the exercise price, the volatility in exchange rate, the contract period and the quoted risk free interest rate during the contract period. b) Valuation techniques and inputs applied for the purpose of measuring Level 3 fair value measurement The fair value of unquoted ordinary shares, unquoted preferred shares, limited partnership and private-placement funds were determined by using market approach and asset-based approach. The significant unobservable inputs were the discount rates for lack of marketability of 10% to 30%. If the discount rates for lack of marketability to the valuation model increased by 1% to reflect reasonably possible alternative assumptions while all other variables held constant, the fair value of the abovementioned investments would have decreased approximately by NT$7,200 thousand and NT$9,700 thousand (US$345 thousand) as of December 31, 2019 and 2020, respectively. The fair values of the unsecured subordinate corporate bonds were determined using income approach based on a discounted cash flow analysis. The significant unobservable input was the discount rate that reflects the credit risk of the counterparty. If the discount rate increased by 0.1% while all other variables held constant, the fair value of the bonds would have decreased approximately by NT$6,000 thousand and NT$5,000 thousand (US$178 thousand) as of December 31, 2019 and 2020, respectively. The fair value of accounts receivables measured at FVTOCI are determined based on the present value of future cash flows that reflect the credit risk of counterparties. Since the discount effect was not significant, the Group measured its fair value by using the nominal values. The fair value of the call option was determined using Black-Scholes Options Pricing Model, of which the significant unobservable input was the discount rate for lack of marketability of 20%. If the discount rate increased by 1% while all other variables held constant, the fair value of the call option would have decreased approximately by NT$855 thousand as of December 31, 2019. c. Categories of financial instruments December 31 2019 2020 NT$ NT$ US$ (Note 4) Financial assets FVTPL Mandatorily at FVTPL $ 5,288,996 $ 6,135,793 $ 218,511 Measured at amortized cost (Note 1) 139,668,804 147,521,583 5,253,618 FVTOCI Equity instruments 755,903 728,398 25,940 Debt instruments 1,014,872 1,012,736 36,066 Trade receivables, net 2,029,690 626,413 22,308 Financial liabilities FVTPL Held for trading 973,571 1,537,208 54,744 Financial liabilities for hedging 3,233,301 11,188,244 398,442 Measured at amortized cost (Note 2) 310,187,110 304,737,749 10,852,485 Note 1: The balances included financial assets measured at amortized cost which comprised cash and cash equivalents, trade and other receivables and other financial assets. Note 2: The balances included financial liabilities measured at amortized cost which comprised short-term borrowings, trade and other payables, bonds payable and long-term borrowings. d. Financial risk management objectives and policies The derivative instruments used by the Group were to mitigate risks arising from ordinary business operations. All derivative transactions entered into by the Group were designated as either hedging or trading. Derivative transactions entered into for hedging purposes must hedge risk against fluctuations in foreign exchange rates and interest rates arising from operating activities. The currencies and the amount of derivative instruments held by the Group must match its hedged assets and liabilities denominated in foreign currencies. The Group’s risk management department monitored risks to mitigate risk exposures, reported unsettled position, transaction balances and related gains or losses to the Group’s chief financial officer on monthly basis. 1) Market risk The Group’s activities exposed it primarily to the financial risks of changes in foreign currency exchange rates and interest rates. Gains or losses arising from fluctuations in foreign currency exchange rates of a variety of derivative financial instruments were approximately offset by those of hedged items. Interest rate risk was not significant due to the cost of capital was expected to be fixed. There had been no change to the Group’s exposure to market risks or the manner in which these risks were managed and measured. a) Foreign currency exchange rate risk The Group had sales and purchases as well as financing activities denominated in foreign currency which exposed the Group to foreign currency exchange rate risk. The Group entered into a variety of derivative financial instruments to hedge foreign currency exchange rate risk to minimize the fluctuations of assets and liabilities denominated in foreign currencies. The carrying amounts of the Group’s foreign currency denominated monetary assets and liabilities (including those eliminated upon consolidation) as well as derivative instruments which exposed the Group to foreign currency exchange rate risk at each balance sheet date are presented in Note 39. The Group was mainly subject to the impact from the exchange rate fluctuation in US$, JPY and HKD against NT$ or RMB. 1% fluctuation is used when reporting foreign currency exchange rate risk internally to key management personnel and represents management’s assessment of the reasonably possible change in foreign currency exchange rates. The sensitivity analysis included financial assets and liabilities and inter-company receivables and payables within the Group. The changes in profit before income tax due to a 1% change in US$, JPY, and HKD against NT$ and RMB would be NT$129,000 thousand, NT$82,000 thousand and NT$35,000 thousand (US$1,246 thousand) for the years ended December 31, 2018, 2019 and 2020, respectively. Hedging contracts and hedged items have been taken into account while measuring the changes in profit before income tax. The abovementioned sensitivity analysis mainly focused on the foreign currency monetary items at each balance sheet date. As the period-end exposure did not reflect the exposure for the years ended December 31, 2018, 2019 and 2020, the abovementioned sensitivity analysis was unrepresentative of those respective years. Hedge accounting The Group’s hedging strategy was to lift borrowings denominated in foreign currencies to avoid exchange rate exposure from its investments in equity instruments denominated in foreign currencies (recognized under the line item of financial assets at FVTPL) and net investment in foreign subsidiary, USIFR, which has EUR as its functional currency. Those transactions were designated as fair value hedges and a hedge of net investment in foreign operation, respectively. Hedge adjustments were made to totally offset the foreign exchange gains or losses from those equity instruments denominated in foreign currencies and foreign operations when they were evaluated based on the exchange rates on each balance sheet date. The hedge ineffectiveness in these hedging relationships arose from the material difference between the notional amounts of borrowings denominated in foreign currencies and the original investments in equity instruments denominated in foreign currencies and net investment in foreign operations. No other sources of ineffectiveness is expected to emerge from these hedging relationships. December 31, 2019 Hedging Instrument/ Line item in Carrying Amount Hedged Items Balance sheet Asset Liability NT$ NT$ Fair value hedge Borrowings denominated in foreign currencies/ Financial assets at FVTPL Financial liabilities for hedging - current $ - $ 3,233,301 Change in Value Used for Calculating Hedge Ineffectiveness Accumulated Gains or Losses in Other Equity Carrying Amount of Hedged Item in Fair Value Hedge Accumulated Amount of Fair Value Hedge Adjustments on Hedged Item Hedging Instrument/ Hedged Item Hedging Instrument Hedged Item Continuing Hedges Hedge Accounting No Longer Applied Asset Asset NT$ NT$ NT$ NT$ NT$ NT$ Fair value hedge Borrowings denominated in foreign currencies/ Financial assets at FVTPL $ 71,743 $ (71,743 ) $ - $ - $ 2,791,574 $ 15,625 December 31, 2020 Hedging Instrument/ Line item in Carrying Amount Hedged Items Balance sheet Asset Liability NT$ US$ (Note 4) NT$ US$ (Note 4) Fair value hedge Borrowings denominated in foreign currencies/ Financial assets at FVTPL Financial liabilities for hedging - current $ - $ - $ 3,307,018 $ 117,771 Hedge of net investment in foreign operation Financial liabilities for hedging - current - - 1,970,307 70,168 Hedge of net investment in foreign operation Financial liabilities for hedging - non-current - - 5,910,919 210,503 Change in Value Used for Calculating Hedge Ineffectiveness Accumulated Gains or Losses in Other Equity Carrying Amount of Hedged Item in Fair Value Hedge Accumulated Amount of Fair Value Hedge Adjustments on Hedged Item Hedging Instrument/ Hedged Item Hedging Instrument Hedged Item Continuing Hedges Hedge Accounting No Longer Applied Asset Asset NT$ NT$ NT$ NT$ NT$ NT$ Fair value hedge Borrowings denominated in foreign currencies/ Financial assets at FVTPL $ 157,842 $ (157,842 ) $ - $ - $ 2,859,132 $ (142,217 ) Hedge of net investment in foreign operation 574,824 (574,824 ) (574,824 ) - - - Change in Value Used for Calculating Hedge Ineffectiveness Accumulated Gains or Losses in Other Equity Carrying Amount of Hedged Item in Fair Value Hedge Accumulated Amount of Fair Value Hedge Adjustments on Hedged Item Hedging Instrument/ Hedged Ite m Hedging Instrument Hedged Item Continuing Hedges Hedge Accounting No Longer Applied Asset Asset US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) Fair value hedge Borrowings denominated in foreign currencies/ Financial assets at FVTPL $ 5,621 $ (5,621 ) $ - $ - $ 101,821 $ (5,065 ) Hedge of net investment in foreign operatio n 20,471 (20,471 ) (20,471 ) - - - b) Interest rate risk Except a portion of long-term borrowings and bonds payable at fixed interest rates, the Group was exposed to interest rate risk because group entities borrowed funds at floating interest rates. Changes in market interest rates led to variances in effective interest rates of borrowings from which the future cash flow fluctuations arise. The Group utilized financing instruments with low interest rates and favorable terms to maintain low financing cost, adequate banking facilities, as well as to hedge interest rate risk. The carrying amounts of th e n December 31 2019 2020 NT$ NT$ US$ (Note 4) Fair value interest rate risk Financial liabilities $ 41,952,056 $ 56,599,417 $ 2,015,649 Cash flow interest rate risk Financial assets 46,467,663 45,489,788 1,620,007 Financial liabilities 169,709,237 131,715,366 4,690,718 For assets and liabilities with floating interest rates, a 100 basis point increase or decrease was used when reporting interest rate risk internally to key management personnel. If interest rates had been 100 basis points (1%) higher or lower and all other variables held constant, the Group’s profit before income tax for the years ended December 31, 2018, 2019 and 2020 would have decreased or increased approximately by NT$1,398,000 thousand, NT$1,232,000 thousand and NT$862,000 thousand (US$30,698 thousand), respectively. Hedging contracts and hedged items have been taken into account while measuring the changes in profit before income tax. The abovementioned sensitivity analysis mainly focused on the interest rate items at the end of each year. As the year-end exposure did not reflect the exposure for the years ended December 31, 2018, 2019 and 2020, the abovementioned sensitivity analysis was unrepresentative of those respective periods. c) Other price risk The Group was exposed to equity price risk through its investments in financial assets at FVTPL and financial assets at FVTOCI. If equity price was 1% higher or lower, profit before income tax for the years ended December 31, 2018, 2019 and 2020 would have increased or decreased approximately by NT$64,000 thousand, NT$51,000 thousand and NT$59,000 thousand (US$2,101 thousand), respectively, and other comprehensive income before income tax for the years ended December 31, 2018, 2019 and 2020 would have increased or decreased approximately by NT$16,000 thousand, NT$8,000 thousand and NT$7,000 thousand (US$249 thousand), respectively. 2) Credit risk Credit risk refers to the risk that counterparty will default on its contractual obligations resulting in financial loss to the Group. The Group’s credit risk arises from cash and cash equivalents, trade and other receivables and other financial assets. The Group’s maximum exposure to credit risk was the carrying amounts of financial assets in the consolidated balance sheets. As of December 31, 2019 and 2020, the Group’s five largest customers accounted for 37% and 27% of trade receivables, respectively. The Group transacts with a large number of unrelated customers and, thus, no concentration of credit risk was observed. 3) Liquidity risk The Group manages liquidity risk by maintaining adequate working capital and banking facilities to fulfill the demand for cash flow used in the Group’s operation and capital expenditure. The Group also monitors its compliance with all the loan covenants. Liquidity risk is not considered to be significant. In the table below, financial liabilities with a repayment on demand clause were included in the earliest time band regardless of the probability of counter-parties choosing to exercise their rights. The maturity dates for other non-derivative financial liabilities were based on the agreed repayment dates. To the extent that interest flows are floating rate, the undiscounted amounts were derived from the interest rates at each balance sheet date. December 31, 2019 On Demand or Less than 1 Month 1 to 3 Months 3 Months to 1 Year 1 to 5 Years More than 5 Years NT$ NT$ NT$ NT$ NT$ Non-derivative financial liabilities Non-interest bearing $ 35,283,757 $ 38,803,904 $ 7,989,256 $ 33,797 $ 184,338 Obligation under leases 75,388 115,297 532,747 1,536,600 4,412,859 Floating interest rate liabilities 10,740,844 6,708,303 18,868,999 133,341,087 7,190,891 Fixed interest rate liabilities 6,819,585 3,712,979 2,281,375 34,405,594 3,689,219 $ 52,919,574 $ 49,340,483 $ 29,672,377 $ 169,317,078 $ 15,477,307 Further information for maturity analysis of obligation under leases was as follows: Less than 1 Year 1 to 5 Years 5 to 10 Years 10 to 15 Years 15 to 20 Years More than 20 Years NT$ NT$ NT$ NT$ NT$ NT$ Obligation under leases $ 723,432 $ 1,536,600 $ 1,454,128 $ 856,825 $ 712,696 $ 1,389,210 December 31, 2020 On Demand or Less than 1 Month 1 to 3 Months 3 Months to 1 Year 1 to 5 Years More than 5 Years NT$ NT$ NT$ NT$ NT$ Non-derivative financial liabilities Non-interest bearing $ 43,111,390 $ 44,122,659 $ 8,223,684 $ 319,510 $ 176,536 Obligation under leases 103,734 151,921 619,908 1,779,041 4,088,301 Floating interest rate liabilities 13,792,596 8,190,076 10,214,154 102,253,481 7,999,130 Fixed interest rate liabilities 11,895,281 528,290 3,349,614 46,900,450 5,631,522 $ 68,903,001 $ 52,992,946 $ 22,407,360 $ 151,252,482 $ 17,895,489 On Demand or Less than 1 Month 1 to 3 Months 3 Months to 1 Year 1 to 5 Years More than 5 Years US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) Non-derivative financial liabilities Non-interest bearing $ 1,535,306 $ 1,571,320 $ 292,866 $ 11,379 $ 6,287 Obligation under leases 3,694 5,410 22,077 63,356 145,595 Floating interest rate liabilities 491,189 291,669 363,752 3,641,506 284,869 Fixed interest rate liabilities 423,621 18,814 119,288 1,670,244 200,553 $ 2,453,810 $ 1,887,213 $ 797,983 $ 5,386,485 $ 637,304 Further information for maturity analysis of obligation under leases was as follows: Less than 1 Year 1 to 5 Years 5 to 10 Years 10 to 15 Years 15 to 20 Years More than 20 Years NT$ NT$ NT$ NT$ NT$ NT$ Obligation under leases $ 875,563 $ 1,779,041 $ 1,422,331 $ 776,735 $ 674,446 $ 1,214,789 Less than 1 Year 1 to 5 Years 5 to 10 Years 10 to 15 Years 15 to 20 Years More than 20 Years US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) Obligation under leases $ 31,181 $ 63,356 $ 50,653 $ 27,661 $ 24,019 $ 43,262 The amounts included above for floating interest rate instruments for non-derivative financial liabilities were subject to change if changes in floating interest rates differ from those estimates of interest rates determined at each balance sheet date. The following table detailed the Group’s liquidity analysis for its derivative financial instruments. The table was based on the undiscounted contractual net cash inflows and outflows on derivative instruments settled on a net basis, and the undiscounted gross cash inflows and outflows on those derivatives that require gross settlement. When the amounts payable or receivable are not fixed, the amounts disclosed have been determined by reference to the projected interest rates as illustrated by the yield curves at each balance sheet date On Demand or Less than 1 Month 1 to 3 Months 3 Months to 1 Year NT$ NT$ NT$ December 31, 2019 Net settled Forward exchange contracts $ (74,864 ) $ (13,246 ) $ - On Demand or Less than 1 Month 1 to 3 Months 3 Months to 1 Year NT$ NT$ NT$ Gross settled Forward exchange contracts Inflows $ 9,296,123 $ 4,420,233 $ 230,354 Outflows (9,248,333 ) (4,392,070 ) (227,848 ) 47,790 28,163 2,506 Swap contracts Inflows 10,187,215 15,025,154 34,327,100 Outflows (10,163,964 ) (15,032,603 ) (34,773,848 ) 23,251 (7,449 ) (446,748 ) $ 71,041 $ 20,714 $ (444,242 ) On Demand or Less than 1 Month 1 to 3 Months 3 Months to 1 Year Over 1 Year NT$ NT$ NT$ NT$ December 31, 2020 Net settled Forward exchange contracts $ 30,514 $ 18,429 $ - $ - Gross settled Forward exchange contracts Inflows $ 8,862,682 $ 5,565,137 $ 531,336 $ - Outflows (8,798,238 ) (5,518,153 ) (526,880 ) - 64,444 46,984 4,456 - Swap contracts Inflows 19,311,999 17,179,871 36,739,200 $ - Outflows (19,524,820 ) (17,486,997 ) (37,495,172 ) - (212,821 ) (307,124 ) (755,972 ) - Target redemption forward contracts Inflows 42,720 96,120 416,520 227,128 Outflows (44,471 ) (100,060 ) (433,595 ) (236,081 ) (1,751 ) (3,940 ) (17,075 ) (8,953 ) $ (150,128 ) $ (264,080 ) $ (768,591 ) $ (8,953 ) On Demand or Less than 1 Month 1 to 3 Months 3 Months to 1 Year Over 1 Year US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) December 31, 2020 Net settled Forward exchange contracts $ 1,087 $ 656 $ - $ - Gross settled Forward exchange contracts Inflows $ 315,623 $ 198,189 $ 18,922 $ - Outflows (313,328 ) (196,516 ) (18,763 ) - 2,295 1,673 159 - On Demand or Less than 1 Month 1 to 3 Months 3 Months to 1 Year Over 1 Year US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) Swap contracts Inflows 687,749 611,819 1,308,376 $ - Outflows (695,328 ) (622,756 ) (1,335,298 ) - (7,579 ) (10,937 ) (26,922 ) - Target redemption forward contracts Inflows 1,522 3,423 14,833 8,089 Outflows (1,584 ) (3,563 ) (15,441 ) (8,408 ) (62 ) (140 ) (608 ) (319 ) $ (5,346 ) $ (9,404 ) $ (27,371 ) $ (319 )

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Related Party Transactions	35. RELATED PARTY TRANSACTIONS Balances and transactions within the Group had been eliminated upon consolidation. Details of transactions between the Group and other related parties were disclosed as follows: a. Related parties In addition to those disclosed in Note 14, the related parties were as follows: Related Parties Relationship with the Company ASE Cultural and Educational Foundation Substantial related party ASE Environmental Protection and Sustainability Foundation Substantial related party b. The Group contributed NT$100,000 thousand (US$3,561 thousand) to ASE Cultural and Educational Foundation in 2018, 2019 and 2020, respectively, for environmental charity in promoting the related domestic environmental protection and public service activities. In December 2020, the Group further resolved to make contributions in the amount of NT$100,000 thousand (US$3,561 thousand) through the ASE Environmental Protection and Sustainability Foundation to continuously implement the activities related to environmental protection projects (Note 37). c. The subsidiary, ASE, and HC entered into a joint development agreement in June 2020 under the concept of joint construction. The agreement stipulates that HC will build the plant on the leasehold land and ASE and its affiliates will have the priority to purchase the plant after the completion of the plant construction. The final transaction price will be the purchase price less an amount based on the ratio calculated by independent professional appraisers. d. As disclosed in Note 31, USIE repurchased its own 2,805 thousand and 2,685 thousand ordinary shares from the Group’s key management personnel with approximately NT$1,247,187 thousand and NT$1,520,976 thousand (US$54,166 thousand) in July 2019 and September 2020, respectively. e. In 2019, ASE purchased real estate properties from associates with the amount of NT$2,326,000 thousand, which was primarily based on the independent professional appraisal reports and has been fully paid in September 2019. f. Compensation to key management personnel For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Short-term employee benefits $ 1,041,216 $ 1,027,191 $ 1,264,980 $ 45,049 Post-employment benefits 3,884 2,208 2,007 72 Share-based payments 9,145 134,544 153,774 5,476 $ 1,054,245 $ 1,163,943 $ 1,420,761 $ 50,597 The compensation to the Group’s key management personnel was determined according to personal performance and market trends.

Assets Pledged as Collateral or

Assets Pledged as Collateral or for Security	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Assets Pledged as Collateral or for Security	36. ASSETS PLEDGED AS COLLATERAL OR FOR SECURITY The following assets were provided as collateral for bank borrowings, tariff guarantees of imported raw materials or collateral: December 31 2019 2020 NT$ NT$ US$ (Note 4) Inventories related to real estate business $ 6,063,303 $ 10,564,873 $ 376,242 Property, plant and equipment 138,831 124,124 4,420 Investment properties 12,167,772 11,847,145 421,907 Other financial assets (including current and non-current) 637,775 460,890 16,414 $ 19,007,681 $ 22,997,032 $ 818,983 As of December 31, 2020, in addition to the abovementioned assets, 89.6% of ownership in FAFG was also provided as collateral for syndicated bank loans.

Significant Contingent Liabilit

Significant Contingent Liabilities and Unrecognized Commitments	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Significant Contingent Liabilities and Unrecognized Commitments	37. SIGNIFICANT CONTINGENT LIABILITIES AND UNRECOGNIZED COMMITMENTS In addition to those disclosed in other notes, significant commitments and contingencies of the Group as of each balance sheet date were as follows: a. As of December 31, 2019 and 2020, unused letters of credit of the Group were approximately NT$394,000 thousand and NT$2,000 thousand (US$71 thousand), respectively. b. As of December 31, 2019 and 2020, the Group’s commitments to purchase property, plant and equipment were approximately NT$25,119,371 thousand and NT$32,627,411 thousand (US$1,161,945 thousand), respectively, of which NT$5,145,345 thousand and NT$1,968,779 thousand (US$70,113 thousand) had been prepaid, respectively. As of December 31, 2019 and 2020, the commitment that the Group has contracted for the construction related to our real estate business were approximately NT$1,393,859 thousand and NT$602,548 thousand (US$21,458 thousand), respectively. c. As of December 31, 2019 and 2020, letters of credits were provided to customs by banks for the importation of goods, and the banking facilities granted to the Group were approximately NT$952,001 thousand and NT$671,721 thousand (US$23,922 thousand), respectively. d. In consideration of corporate social responsibility for environmental protection, the board of directors of ASE, in December 2013, approved contributions to be made in the next 30 years, at a total amount of NT$3,000,000 thousand (US$106,838 thousand), at the minimum, to environmental protection efforts in Taiwan.

Others

Others	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Others	38. OTHERS a. There were five employees and a waste disposal supplier of a subsidiary in China accused by China People’s Procuratorate (the “Procuratorate”) for committing the crime of environmental pollution in 2018. During the trial, the Procuratorate claimed that the subsidiary should also be charged with corporate crime which caused the subsidiary received a change and addition indictment in October 2019. In June 2020, in the first trial, the court of first instance ruled that the subsidiary shall be imposed a fine of RMB400 thousand and return the benefit (RMB344 thousand) generated from such violation. Both of the fine and the return of benefit from violation were recognized by the subsidiary under the line item of other gains and losses. Because some of co-defendants have filed an appeal against the judgment and, pursuant to local applicable law, the whole case will be deemed appealed, this case was not yet final and moved to the court of second instance for trial. As of the date that the consolidated financial statements were authorized for issue, final results of the indemnification could not be reliably measured. b. On December 20, 2013, the Kaohsiung Environmental Protection Bureau (the “KEPB”) imposed an administrative fine of NT$102,014 thousand (the “Original Fine”) upon ASE for violation of the Water Pollution Control Act. After ASE sought administrative remedies against the Original Fine, the Original Fine has been revoked by final judgment of Supreme Administrative Court on June 8, 2017, and KEPB is ordered to refund the Original Fine to ASE. On December 27, 2019, KEPB has refunded NT$55,062 thousand to ASE. On February 10, 2020, KEPB re-imposed an administrative fine of NT$46,952 thousand (US$1,672 thousand) (the “New Fine”) upon ASE and offset the New Fine by the remaining amount which shall be refunded to ASE. Therefore, no additional payment that ASE should make for the New Fine. After ASE filed an administrative appeal against the New Fine, the Administrative Appeal Review Committee of Kaohsiung City Government has revoked the New Fine on December 15, 2020 and remanded to KEPB for another legitimate administrative action.

Significant Subsequent Events

Significant Subsequent Events	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Significant Subsequent Events	39. SIGNIFICANT SUBSEQUENT EVENTS On March 1, 2021, the subsidiary, USISH, issued unsecured convertible corporate bonds of RMB3,450,000 thousand with a six-year term and the annual interest rates are 0.1%, 0.2%, 0.6%, 1.3%, 1.8% and 2.0%, respectively, for the respective year.

Significant Assets and Liabilit

Significant Assets and Liabilities Denominated in Foreign Currencies	12 Months Ended
	Dec. 31, 2020
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Significant Assets and Liabilities Denominated in Foreign Currencies	40. SIGNIFICANT ASSETS AND LIABILITIES DENOMINATED IN FOREIGN CURRENCIES The following information was aggregated by the foreign currencies other than functional currencies of the group entities and the exchange rates between foreign currencies and respective functional currencies were disclosed. The significant financial assets and liabilities denominated in foreign currencies were as follows: Foreign Currencies (In Thousand) Exchange Rate Carrying Amount (In Thousand) December 31, 2019 Monetary financial assets US$ $ 4,125,872 US$1=NT$29.98 $ 123,693,628 US$ 1,189,539 US$1=RMB6.9762 35,662,384 JPY 13,889,872 JPY1=NT$0.2760 3,833,605 JPY 771,392 JPY1=US$0.0092 212,904 Monetary financial liabilities US$ 3,823,359 US$1=NT$29.98 114,624,313 US$ 1,211,472 US$1=RMB6.9762 36,319,926 JPY 14,628,543 JPY1=NT$0.2760 4,037,478 JPY 815,929 JPY1=US$0.0092 225,197 December 31, 2020 Monetary financial assets US$ 4,269,075 US$1=NT$28.48 121,583,265 US$ 1,527,381 US$1=RMB6.5249 43,499,803 US$ 41,643 EUR1=US$0.8143 1,185,984 JPY 13,544,360 JPY1=NT$0.2763 3,742,306 JPY 1,174,208 JPY1=US$0.0097 324,434 HKD 174,765 HKD1=NT$3.6730 641,912 Monetary financial liabilities US$ 4,439,915 US$1=NT$28.48 126,448,786 US$ 1,517,568 US$1=RMB6.5249 43,220,325 US$ 20,896 EUR1=US$0.8143 595,128 JPY 13,657,967 JPY1=NT$0.2763 3,773,695 JPY 1,188,650 JPY1=US$0.0097 328,424 HKD 18,814 HKD1=NT$3.6730 69,103 The significant realized and unrealized foreign exchange gain (loss) were as follows: For the Year Ended December 31 2018 2019 2020 Functional Currencies Exchange Rate Net Foreign Exchange Loss Exchange Rate Net Foreign Exchange Gain (Loss) Exchange Rate Net Foreign Exchange Gain (Loss) NT$ NT$ NT$ US$ (Note 4) US$ US$1=NT$30.715 $ (67,476 ) US$1=NT$29.98 $ (84,177 ) US$1=NT$28.48 $ (143,804 ) $ (5,121 ) NT$ (849,234 ) 1,203,823 1,382,067 49,219 RMB RMB1=NT$4.4753 (120,005 ) RMB1=NT$4.2975 14,055 RMB1=NT$4.3648 (181,624 ) (6,468 ) $ (1,036,715 ) $ 1,133,701 $ 1,056,639 $ 37,630

Operating Segments Information

Operating Segments Information	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Operating Segments Information	41. OPERATING SEGMENTS INFORMATION The Group has the following reportable segments: Packaging, Testing and EMS. The Group packages bare semiconductors into finished semiconductors with enhanced electrical and thermal characteristics; provides testing services, including front-end engineering testing, wafer probing and final testing services; engages in the designing, assembling, manufacturing and sale of electronic components and telecommunications equipment motherboards. Information about other business activities and operating segments that are not reportable are combined and disclosed in “Others.” The Group engages in other activities such as substrate production as well as sale and leasing of real estate properties. The accounting policies for segments are the same as those described in Note 4. The measurement basis for resources allocation and performance evaluation is based on profit before income tax. a. Segment revenues and operation results Adjustments Packaging Testing EMS Others and Eliminations Total NT$ NT$ NT$ NT$ NT$ NT$ For the year ended December 31, 2018 Revenue from external customers 178,308,222 35,903,202 151,890,384 4,990,613 - 371,092,421 Inter-group revenues (Note 1) 3,531,431 212,310 58,836,465 7,637,053 (70,217,259 ) - Segment revenues 181,839,653 36,115,512 210,726,849 12,627,666 - 441,309,680 Interest income 166,761 55,108 354,343 352,232 (462,233 ) 466,211 Interest expense (3,647,601 ) (101,338 ) - (249,180 ) 462,233 (3,535,886 ) Depreciation and amortization (29,491,977 ) (9,560,610 ) (2,065,590 ) (1,570,726 ) - (42,688,903 ) Share of the profit or loss of associates and joint ventures (456,846 ) (23,398 ) - - - (480,244 ) Impairment loss (654,081 ) - - - - (654,081 ) Segment profit before income tax 17,866,431 7,952,484 6,225,984 (107,221 ) - 31,937,678 Expenditures for segment assets 22,787,190 12,991,023 2,529,771 784,254 - 39,092,238 December 31, 2018 Investments accounted for using the equity method 9,152,290 160,018 - - - 9,312,308 Contract assets 3,488,372 1,000,128 - - - 4,488,500 For the year ended December 31, 2019 Revenue from external customers 198,916,897 42,658,686 165,789,479 5,817,122 - 413,182,184 Inter-group revenues (Note 1) 5,370,963 231,399 60,638,567 7,431,399 (73,672,328 ) - Segment revenues 204,287,860 42,890,085 226,428,046 13,248,521 - 486,854,512 Interest income 186,291 90,091 249,487 284,458 (260,646 ) 549,681 Interest expense (3,403,475 ) (545,609 ) (255,404 ) (243,013 ) 260,646 (4,186,855 ) Depreciation and amortization (33,456,831 ) (12,379,703 ) (2,534,825 ) (2,095,482 ) - (50,466,841 ) Share of the profit or loss of associates and joint ventures 75,303 39,852 67,120 - - 182,275 Impairment loss (601,066 ) (141 ) - - - (601,207 ) Segment profit before income tax 7,572,763 10,321,537 6,082,106 (696,595 ) - 23,279,811 Expenditures for segment assets 35,462,305 23,966,051 2,770,129 875,402 - 63,073,887 December 31, 2019 Investments accounted for using the equity method 8,867,316 1,123,490 2,094,401 - - 12,085,207 Contract assets 4,162,124 1,735,192 - - - 5,897,316 For the year ended December 31, 2020 Revenue from external customers 218,666,071 47,271,074 204,690,669 6,350,896 - 476,978,710 Inter-group revenues (Note 1) 10,436,168 435,587 21,472,775 7,234,303 (39,578,833 ) - Segment revenues 229,102,239 47,706,661 226,163,444 13,585,199 - 516,557,543 Interest income 133,160 79,821 275,766 32,036 - 520,783 Interest expense (2,244,280 ) (564,269 ) (443,519 ) (185,160 ) - (3,437,228 ) Depreciation and amortization (32,333,229 ) (14,189,024 ) (2,877,546 ) (1,859,266 ) - (51,259,065 ) Share of the profit or loss of associates and joint ventures 362,133 99,670 85,809 - - 547,612 Impairment loss (218,600 ) (773,673 ) - - - (992,273 ) Segment profit before income tax 17,476,440 10,277,760 8,438,766 (424,168 ) - 35,768,798 Expenditures for segment assets 38,643,303 14,275,397 5,614,409 491,092 - 59,024,201 December 31, 2020 Investments accounted for using the equity method 9,146,344 1,340,307 2,320,022 - - 12,806,673 Contract assets 3,641,244 1,141,660 - - - 4,782,904 Adjustments Packaging Testing EMS Others and Eliminations Total US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) For the year ended December 31, 2020 Revenue from external customers 7,787,253 1,683,443 7,289,554 226,171 - 16,986,421 Inter-group revenues (Note 1) 371,659 15,512 764,700 257,632 (1,409,503 ) - Segment revenues 8,158,912 1,698,955 8,054,254 483,803 - 18,395,924 Interest income 4,742 2,842 9,821 1,141 - 18,546 Interest expense (79,925 ) (20,095 ) (15,795 ) (6,594 ) - (122,409 ) Depreciation and amortization (1,151,468 ) (505,307 ) (102,477 ) (66,213 ) - (1,825,465 ) Share of the profit or loss of associates and joint ventures 12,896 3,550 3,056 - - 19,502 Impairment loss (7,785 ) (27,552 ) - - - (35,337 ) Segment profit before income tax 622,380 366,017 300,526 (15,106 ) - 1,273,817 Expenditures for segment assets 1,376,186 508,383 199,943 17,489 - 2,102,001 December 31, 2020 Investments accounted for using the equity method 325,724 47,732 82,622 - - 456,078 Contract assets 129,674 40,657 - - - 170,331 Note 1: Inter-group revenues were eliminated upon consolidation. Note 2: The disaggregated product and service type from the Group's contract with customer is the same as those disclosed in above reportable segment. b. Revenue from major products and services For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Packaging service $ 178,308,222 $ 198,916,897 $ 218,666,071 $ 7,787,253 Testing service 35,903,202 42,658,686 47,271,074 1,683,443 EMS 151,890,384 165,789,479 204,690,669 7,289,554 Others 4,990,613 5,817,122 6,350,896 226,171 $ 371,092,421 $ 413,182,184 $ 476,978,710 $ 16,986,421 c. Geographical information The Group’s revenue from external customers by location of headquarter and information about its non-current assets by location of assets are detailed below. 1) Net revenues from external customers For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) United States $ 230,791,164 $ 245,521,027 $ 297,117,001 $ 10,581,090 Taiwan 45,630,792 51,244,470 64,829,301 2,308,736 Asia 56,031,108 75,938,364 74,447,091 2,651,249 Europe 36,844,258 38,613,132 39,477,306 1,405,887 Others 1,795,099 1,865,191 1,108,011 39,459 $ 371,092,421 $ 413,182,184 $ 476,978,710 $ 16,986,421 2) Non-current assets December 31 2019 2020 NT$ NT$ US$ (Note 4) Taiwan $ 239,532,971 $ 239,353,978 $ 8,524,002 China 68,747,648 63,907,990 2,275,926 Others 26,645,450 34,107,657 1,214,660 $ 334,926,069 $ 337,369,625 $ 12,014,588 Non-current assets exclude financial instruments, post-employment benefit assets, and deferred tax assets. d. Major customers Except customer A from which the operating revenues generated from packaging and EMS segments were NT$92,117,839, NT$103,987,781 thousand and NT$145,952,908 thousand (US$5,197,753 thousand) for the years ended December 31, 2018, 2019 and 2020, respectively, and customer B from which the operating revenues generated from packaging and testing segments was NT$44,653,072 thousand for the year ended December 31, 2019, the Group did not have any other individual customer from which the operating revenues exceeded 10% of operating revenues for the years ended December 31, 2018, 2019 and 2020.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Statement of Compliance	a. Statement of compliance The consolidated financial statements have been prepared in accordance with IFRSs as issued by the IASB.
Basis of Preparation	b. Basis of preparation The consolidated financial statements have been prepared on the historical cost basis except for financial instruments measured at fair value and net defined benefit liabilities which are measured at the present value of the defined benefit obligation less the fair value of plan assets. The fair value measurements, which are grouped into Levels 1 to 3 based on the degree to which the fair value measurement inputs are observable and based on the significance of the inputs to the fair value measurement in its entirety, are described as follows: 1) Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities; 2) Level 2 inputs are inputs other than quoted prices included within Level 1 that are observable for an asset or a liability, either directly (i.e. as prices) or indirectly (i.e. derived from prices); and 3) Level 3 inputs are unobservable inputs for an asset or a liability.
Classification of Current and Non-current Assets and Liabilities	c. Classification of current and non-current assets and liabilities Current assets include cash and cash equivalents and those assets held primarily for trading purposes or expected to be realized within twelve months after the balance sheet date, unless the asset is to be used for an exchange or to settle a liability, or otherwise remains restricted, at more than twelve months after the balance sheet date. Current liabilities are obligations incurred for trading purposes or to be settled within twelve months after the balance sheet date (even if an agreement to refinance, or to reschedule payments, on a long-term basis is completed after the balance sheet date and before the consolidated financial statements are authorized for issue) and liabilities that do not have an unconditional right to defer settlement for at least 12 months after the balance sheet date (terms of a liability that could, at the option of the counterparty, result in its settlement by the issue of equity instruments do not affect its classification). Assets and liabilities that are not classified as current are classified as non-current. The Group engages in the construction business which has an operating cycle of over one year. The normal operating cycle applies when considering the classification of the Group’s construction-related assets and liabilities.
Basis of Consolidation	d. Basis of consolidation 1) Principles for preparing consolidated financial statements The consolidated financial statements incorporate the financial statements of the Company and the entities controlled by the Company (i.e. its subsidiaries). Income and expenses of subsidiaries acquired or disposed of during the period are included in the consolidated statement of profit or loss and other comprehensive income from the effective dates of acquisitions up to the effective dates of disposals, as appropriate. When necessary, adjustments are made to the financial statements of subsidiaries to bring their accounting policies into line with those used by the Company. All intra-group transactions, balances, income and expenses are eliminated in full upon consolidation. Total comprehensive income of subsidiaries is attributed to the owners of the Company and to the non-controlling interests even if this results in the non-controlling interests having a deficit balance. 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 interests of the Group 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 the owners of the Company. When the Group loses control of a subsidiary, a gain or loss is recognized in profit or loss and is calculated as the difference between (i) the aggregate of the fair value of the consideration received and any investment retained in the former subsidiary at its fair value at the date when control is lost and (ii) the assets (including any goodwill) and liabilities and any non-controlling interests of the former subsidiary at their carrying amounts at the date when control is lost. The Group accounts for all amounts recognized in other comprehensive income in relation to that subsidiary on the same basis as would be required had the Group directly disposed of the related assets or liabilities. 2) Subsidiaries included in consolidated financial statements were as follows: Establishment Percentage of Ownership (%) and Operating December December Name of Investor Name of Investee Main Businesses Location 31, 2019 31, 2020 The Company ASE Engaged in the packaging and testing of semiconductors R.O.C. 100.0 100.0 USI Inc. (“USIINC”) Holding company R.O.C. 100.0 100.0 SPIL Engaged in the assembly, testing and turnkey services of integrated circuit R.O.C. 100.0 100.0 ASE A.S.E. Holding Limited Holding company Bermuda 100.0 100.0 J & R Holding Limited (“J&R Holding”) Holding company Bermuda 100.0 100.0 Innosource Limited Holding company British Virgin Islands 100.0 100.0 Omniquest Industrial Limited Holding company British Virgin Islands 71.0 71.0 ASE Marketing & Service Japan Co., Ltd. Engaged in marketing and sales services Japan 100.0 100.0 ASE Test, Inc. Engaged in the testing of semiconductors R.O.C. 100.0 100.0 Luchu Development Corporation Engaged in the development of real estate properties R.O.C. 67.1 67.1 ASE Embedded Electronics Inc. (“ASEEE”) Merged into ASE in February 2020 R.O.C. 100.0 - Advanced Microelectronic Products Inc. (“AMPI”) Engaged in the manufacturing of integrated circuit R.O.C. 7.6 7.6 ASE Test, Inc. Alto Enterprises Limited Holding company British Virgin Islands 100.0 100.0 Super Zone Holdings Limited Holding company Hong Kong 100.0 100.0 Luchu Development Corporation Engaged in the development of real estate properties R.O.C. 19.0 19.0 TLJ Intertech Inc. Engaged in information software services R.O.C. 60.0 60.0 MingFeng Information Service Corp., Ltd. Engaged in information software services R.O.C. 100.0 100.0 AMPI Engaged in the manufacturing of integrated circuit R.O.C. 43.4 43.4 A.S.E. Holding Limited ASE Investment (Labuan) Inc. Holding company Malaysia 70.1 70.1 ASE Test Limited (“ASE Test”) Holding company Singapore 10.2 10.2 J&R Holding ASE Test Holding company Singapore 89.8 89.8 Omniquest Industrial Limited Holding company British Virgin Islands 8.4 8.4 J&R Industrial Inc. Engaged in leasing equipment and investing activity R.O.C. 100.0 100.0 ASE Japan Co., Ltd. (“ASE Japan”) Engaged in the packaging and testing of semiconductors Japan 100.0 100.0 ASE (U.S.) Inc. After-sales service and sales support U.S.A. 100.0 100.0 Global Advanced Packaging Technology Limited Holding company British Cayman Islands 100.0 100.0 Anstock Limited Engaged in financing activity British Cayman Islands 100.0 100.0 Anstock II Limited Engaged in financing activity British Cayman Islands 100.0 100.0 Suzhou ASEN Semiconductors Co., Ltd. (“ASEN”) Engaged in the packaging and testing of semiconductors Suzhou, China 100.0 100.0 Innosource Limited Omniquest Industrial Limited Holding company British Virgin Islands 20.6 20.6 ASE (Shanghai) Inc. Engaged in the production of substrates Shanghai, China 8.5 8.5 Omniquest Industrial Limited ASE Corporation Holding company British Cayman Islands 100.0 100.0 Alto Enterprises Limited ASE (Kunshan) Inc. Engaged in the packaging and testing of semiconductors Kun Shan, China 22.9 22.9 ASE Investment (Kun Shan) Limited Holding company Kun Shan, China 85.9 85.9 Super Zone Holdings Limited Advanced Semiconductor Engineering (China) Ltd. Engaged in the packaging and testing of semiconductors Shanghai, China 100.0 100.0 ASE Investment (Labuan) Inc. ASE (Korea) Inc. (“ASE Korea”) Engaged in the packaging and testing of semiconductors Korea 100.0 100.0 ASE Korea ASE WeiHai Inc. Engaged in the packaging and testing of semiconductors Shandong, China 100.0 100.0 ASE Test ASE Test Holdings, Ltd. Holding company British Cayman Islands 100.0 100.0 ASE Holdings (Singapore) Pte Ltd Holding company Singapore 100.0 100.0 ASE Investment (Labuan) Inc. Holding company Malaysia 29.9 29.9 ASE Singapore Pte. Ltd. Engaged in the packaging and testing of semiconductors Singapore 100.0 100.0 ASE Test Holdings, Ltd. ISE Labs, Inc. Engaged in the testing of semiconductors U.S.A. 100.0 100.0 Establishment Percentage of Ownership (%) and Operating December December Name of Investor Name of Investee Main Businesses Location 31, 2019 31, 2020 ISE Labs, Inc. ISE Services, Inc. Engaged in wafer procurement and customer product management services and commenced operations in February 2020 U.S.A. - 100.0 ASE Holdings (Singapore) Pte Ltd ASE Electronics (M) Sdn. Bhd. Engaged in the packaging and testing of semiconductors Malaysia 100.0 100.0 Global Advanced Packaging Technology Limited ASE Assembly & Test (Shanghai) Limited (“ASESH”) Engaged in the packaging and testing of semiconductors Shanghai, China 100.0 100.0 ASE Advanced Semiconductor (Shanghai) Limited Engaged in the packaging and testing of semiconductors and was established and spun off from ASESH in November 2020 Shanghai, China - 100.0 ASESH ASE Investment (Kun Shan) Limited Holding company Kun Shan, China 14.1 14.1 Wuxi Tongzhi Microelectronics Co., Ltd. Engaged in the packaging and testing of semiconductors Wuxi, China 100.0 100.0 ISE Labs, China, Ltd. Engaged in the testing of semiconductor Shanghai, China 100.0 100.0 Shanghai Ding Hui Real Estate Development Co., Ltd. (“DH”) Engaged in the development, construction and sale of real estate properties Shanghai, China 60.0 60.0 DH Shanghai Ding Qi Property Management Co., Ltd. Engaged in the management of real estate properties Shanghai, China 100.0 100.0 Shanghai Ding Wei Real Estate Development Co., Ltd. (“DW”) Engaged in the development, construction and leasing of real estate properties Shanghai, China 100.0 100.0 Shanghai Ding Yu Real Estate Development Co., Ltd. Engaged in the development, construction and leasing of real estate properties Shanghai, China 100.0 100.0 Kun Shan Ding Hong Real Estate Development Co., Ltd Engaged in the development, construction and leasing of real estate properties Kun Shan, China 100.0 100.0 Shanghai Ding Xu Property Management Co., Ltd. Engaged in the management of real estate properties Shanghai, China 100.0 100.0 Shanghai Dingyao Estate Development Co., Ltd. Engaged in property management and was invested in April 2020 Shanghai, China - 100.0 Shanghai Ding Fan Business Management Co., Ltd. (The name was changed on June 2020 and the former name was Shanghai Ding Fan Department Store Co., Ltd.) Engaged in the management of real estate properties (acquired from DW in November 2020) Shanghai, China - 100.0 DW Shanghai Ding Fan Business Management Co., Ltd. (The name was changed on June 2020 and the former name was Shanghai Ding Fan Department Store Co., Ltd.) Engaged in leasing and management of real estate properties (disposed to DH in November 2020) Shanghai, China 100.0 - ASE Investment (Kun Shan) Limited ASE (Kunshan) Inc. Engaged in the packaging and testing of semiconductors Kun Shan, China 49.3 49.3 ASE Corporation ASE Mauritius Inc. Holding company Mauritius 100.0 100.0 ASE Labuan Inc. Holding company Malaysia 100.0 100.0 ASE Mauritius Inc. ASE (Kunshan) Inc. Engaged in the packaging and testing of semiconductors Kun Shan, China 27.8 27.8 ASE (Shanghai) Inc. Engaged in the production of substrates Shanghai, China 91.5 91.5 ASE Labuan Inc. ASE Electronics Inc. Engaged in the production of substrates R.O.C. 100.0 100.0 ASE (Shanghai) Inc. Advanced Semiconductor Engineering (HK) Limited Engaged in the trading of substrates Hong Kong 100.0 100.0 Shanghai Ding Hui Real Estate Development Co., Ltd. Engaged in the development, construction and sale of real estate properties Shanghai, China 40.0 40.0 Universal Scientific Industrial (Shanghai) Co., Ltd. (“USISH”) Engaged in the designing, manufacturing and sales of electronic components Shanghai, China 0.8 0.8 USIINC Huntington Holdings International Co., Ltd. Holding company British Virgin Islands 100.0 100.0 Huntington Holdings International Co., Ltd. Unitech Holdings International Co., Ltd. Holding company British Virgin Islands 100.0 100.0 Real Tech Holdings Limited Holding company British Virgin Islands 100.0 100.0 Universal ABIT Holding Co., Ltd. In the process of liquidation British Cayman Islands 100.0 100.0 Real Tech Holdings Limited Universal Scientific Industrial (Kunshan) Co., Ltd. Liquidated in June 2020 Kun Shan, China 100.0 - USI Enterprise Limited (“USIE”) Engaged in the service of investment advisory and warehousing management Hong Kong 95.8 95.9 USIE USISH Engaged in the designing, manufacturing and sales of electronic components Shanghai, China 77.7 76.6 USISH Universal Global Technology Co., Limited Holding company Hong Kong 100.0 100.0 Establishment Percentage of Ownership (%) and Operating December December Name of Investor Name of Investee Main Businesses Location 31, 2019 31, 2020 Universal Global Technology (Kunshan) Co., Ltd. (“UGKS”) Engaged in the designing and manufacturing of electronic components Kun Shan, China 100.0 100.0 Universal Global Technology (Shanghai) Co., Ltd. Engaged in the processing and sales of computer and communication peripherals as well as business in import and export of goods and technology Shanghai, China 100.0 100.0 Universal Global Electronics (Shanghai) Co., Ltd. Engaged in the sales of electronic components and telecommunications equipment Shanghai, China 100.0 100.0 USI Electronics (Shenzhen) Co., Ltd. Engaged in the design, manufacturing and sales of motherboards and computer peripherals Shenzhen, China 50.0 50.0 Huanrong Electronics (Huizhou) Co., Ltd. Engaged in the research and manufacturing of new electronic applications, communications, computers and other electronics products and also provided auxiliary technical services as well as import and export services (acquired from Universal Global Electronics (Shanghai) Co., Ltd. in November 2020) Huizhou, China - 100.0 FINANCIERE AFG (“ ） Holding company France - 10.4 Universal Global Technology Co., Limited Universal Global Industrial Co., Limited Engaged in manufacturing, trading and investing activity Hong Kong 100.0 100.0 Universal Global Scientific Industrial Co., Ltd. (“UGTW”) Engaged in the manufacturing of components of telecomm and cars and provision of related R&D services R.O.C. 100.0 100.0 USI America Inc. Engaged in the manufacturing and processing of motherboards and wireless network communication and provision of related technical service U.S.A. 100.0 100.0 Universal Scientific Industrial De Mexico S.A. De C.V. Engaged in the assembling of motherboards and computer components Mexico 100.0 100.0 USI Japan Co., Ltd. Engaged in the manufacturing and sales of computer peripherals, integrated chip and other related accessories Japan 100.0 100.0 USI Electronics (Shenzhen) Co., Ltd. Engaged in the design, manufacturing and sales of motherboards and computer peripherals Shenzhen, China 50.0 50.0 Universal Global Electronics Co., Ltd. Engaged in accepting and outsourcing orders as well as sales of electronic components and service of technical advisory Hong Kong 100.0 100.0 Universal Scientific Industrial (France) (“USIFR”) Engaged in investing activities and was established in August 2019 France 100.0 100.0 Universal Scientific Industrial Vietnam Company Limited Engaged in IC assembly for wearable devices and was established in July 2020. Vietnam - 100.0 Universal Global Industrial Co., Limited Universal Scientific Industrial De Mexico S.A. De C.V. Engaged in the assembling of motherboards and computer components Mexico (Note) (Note) UGTW Universal Scientific Industrial Co., Ltd. (“USI”) Engaged in the manufacturing, processing and sales of computers, computer peripherals and related accessories R.O.C. 100.0 100.0 USI Electronics (Shenzhen) Co., Ltd. Huanrong Electronics (Huizhou) Co., Ltd. Engaged in the research and manufacturing of new electronic applications, communications, computers and other electronics products and also provided auxiliary technical services as well as import and export services (disposed to USISH in November 2020) Huizhou, China 100.0 - Universal Global Electronics Co., Ltd. Semicondutores Avancados do Brasil S.A. Liquidated in December 2020 Brasil 75.0 - Universal Scientific Industrial Poland Sp. z o.o. (“USIPL”) (The name was changed on June 2020 and the former name was Chung Hong Electronics Poland Sp. z o.o.) Engaged in the design and manufacturing of electronic components and new electronic applications Poland 60.0 100.0 Universal Global Electronics (Shanghai) Co., Ltd. USI Science and Technology (Shenzhen) Co., Ltd. Engaged in the design of electronic components, service of technical advisory; wholesale of electronic components and communication peripherals as well as business in import and export of goods and management of properties and was established in November 2020. Shenzhen, China - 100.0 USIFR FAFG Holding company France - 89.6 ASTEELFLASH GROUP Holding company France - (Note) Establishment Percentage of Ownership (%) and Operating December December Name of Investor Name of Investee Main Businesses Location 31, 2019 31, 2020 FAFG ASTEELFLASH GROUP Holding company France - 100.0 MANUFACTURING POWER TUNISIA Engaged in the design and manufacturing of electronic components Tunisia 0.1 ASTEELFLASH MEXICO S.A. de C.V. Engaged in the design and manufacturing of electronic components Mexico 0.1 ASTEELFLASH GROUP ASTEELFLASH (BEDFORD) LIMITED Engaged in the design and manufacturing of electronic components United Kingdom - 100.0 ASTEELFLASH FRANCE Engaged in the design and manufacturing of electronic components France - 99.9 ASTEELFLASH TUNISIE S.A. Engaged in the design and manufacturing of electronic components Tunisia - 100.0 ASTEELFLASH HONG KONG LIMITED Holding company Hong Kong - 100.0 ASTEELFLASH MEXICO S.A. de C.V. Engaged in the design and manufacturing of electronic components Mexico - 99.9 ASTEELFLASH GERMANY GmbH Engaged in the design and manufacturing of electronic components Germany - 100.0 MANUFACTURING POWER TUNISIA Engaged in the design and manufacturing of electronic components Tunisia - 99.9 ASTEELFLASH US HOLDING CORP. Holding company U.S.A. - 100.0 ASTEEL ELECTRONIQUE FOUCHANA Engaged in the design and manufacturing of electronic components Tunisia - (Note) AFERH TUNISIE Engaged in the management, training and consulting of human resources Tunisia - 0.5 ASTEEL ELECTRONICS MANUFACTURING SERVICES Engaged in the design and manufacturing of electronic components Tunisia 0.1 ASTEELFLASH (BEDFORD) LIMITED ASTEELFLASH TUNISIE S.A. Engaged in the design and manufacturing of electronic components Tunisia - (Note) ASTEELFLASH TECHNOLOGIE ASTEELFLASH FRANCE Engaged in the design and manufacturing of electronic components France - (Note) ASTEELFLASH FRANCE SCI CHASSET Engaged in the management and operation of real estate properties and holding the ownership of real estate properties France - 100.0 AFERH Engaged in the management, training and consulting of human resources France - 100.0 ASTEEL ELECTRONICS MANUFACTURING SERVICES Engaged in the design and manufacturing of electronic components Tunisia - 99.9 ASTEEL ELECTRONIQUE FOUCHANA Engaged in the design and manufacturing of electronic components Tunisia - 94.2 ASTEELFLASH TECHNOLOGIE Engaged in projection of plastic and the design and manufacturing of industrial components France - 100.0 ASTEELFLASH BRETAGNE Engaged in the design and manufacturing of electronic components France - 100.0 ASTEELFLASH TUNISIE S.A. Engaged in the design and manufacturing of electronic components Tunisia - (Note) ASTEELFLASH TUNISIE S.A. ASTEEL ELECTRONIQUE TUNISIE Engaged in the design and manufacturing of electronic components Tunisia - 100.0 ASTEEL ELECTRONIQUE FOUCHANA Engaged in the design and manufacturing of electronic components Tunisia (Note) AFERH AFERH TUNISIE Engaged in the management, training and consulting of human resources Tunisia - 99.5 ASTEELFLASH HONG KONG LIMITED ASTEELFLASH SUZHOU CO., LTD. Engaged in the design and manufacturing of electronic components Suzhou, China - 100.0 ASTEELFLASH SUZHOU CO., LTD. ASTEEL ELECTRONIQUE FOUCHANA Engaged in the design and manufacturing of electronic components Tunisia - (Note) ASTEELFLASH TUNISIE S.A. Engaged in the design and manufacturing of electronic components Tunisia - (Note) ASTEELFLASH GERMANY GmbH ASTEELFLASH HERSFELD GmbH Engaged in the design and manufacturing of electronic components Germany - 100.0 ASTEELFLASH EBERBACH GmbH Engaged in the design and manufacturing of electronic components Germany - 100.0 ASTEELFLASH BONN GmbH Engaged in the design and manufacturing of electronic components Germany - 100.0 ASTEELFLASH SCHWANDORF GmbH Engaged in the design and manufacturing of electronic components Germany - 100.0 ASTEELFLASH PLZEN S.R.O. Engaged in the design and manufacturing of electronic components Czech Republic - 100.0 ASTEELFLASH DESIGN SOLUTIONS HAMBOURG GmbH Engaged in the design and manufacturing of electronic components Germany - 100.0 EN ELECTRONICNETWORK SRL Engaged in the design and manufacturing of electronic components Romania - 100.0 Establishment Percentage of Ownership (%) and Operating December December Name of Investor Name of Investee Main Businesses Location 31, 2019 31, 2020 ASTEELFLASH TUNISIE S.A. Engaged in the design and manufacturing of electronic components Tunisia - (Note) ASTEELFLASH MEXICO S.A. de C.V. ASTEELFLASH TUNISIE S.A. Engaged in the design and manufacturing of electronic components Tunisia - (Note) ASTEELFLASH US HOLDING CORP. ASTEELFLASH USA CORP. Engaged in the design and manufacturing of electronic components U.S.A. - 100.0 ASTEELFLASH USA CORP. ASTEEL ELECTRONIQUE FOUCHANA Engaged in the design and manufacturing of electronic components Tunisia - (Note) ASTEELFLASH TUNISIE S.A. Engaged in the design and manufacturing of electronic components Tunisia - (Note) SPIL SPIL (B.V.I.) Holding Limited Engaged in investing activities British Virgin Islands 100.0 100.0 Siliconware Investment Co., Ltd. Engaged in investing activities R.O.C. 100.0 100.0 SPIL (B.V.I.) Holding Limited Siliconware USA, Inc. Engaged in marketing activities U.S.A. 100.0 100.0 SPIL (Cayman) Holding Limited Engaged in investing activities British Cayman Islands 100.0 100.0 SPIL (Cayman) Holding Limited Siliconware Technology (Suzhou) Limited (“SZ”) Engaged in the packaging and testing of semiconductors Suzhou, China 100.0 100.0 Siliconware Electronics (Fujian) Co., Limited (“SF”) Engaged in the packaging and testing of semiconductors and was disposed in October 2020 (Note 30) Fujian, China 100.0 - Note: The number of shares held is 1 share or 3 shares and representing less than 0.1% of total shares.
Business Combinations	e. Business combination s Acquisitions of businesses are accounted for using the acquisition method. Acquisition-related costs are generally recognized in profit or loss as they are incurred. Goodwill is measured as the excess of the sum of the consideration transferred, the amount of any non-controlling interests in the acquiree, and the fair value of the acquirer’s previously held equity interest in the acquiree (if any) over the net of the acquisition-date amounts of the identifiable assets acquired and the liabilities assumed. If, after re-assessment, the net of the acquisition-date amounts of the identifiable assets acquired and liabilities assumed exceeds the sum of the consideration transferred, the amount of any non-controlling interests in the acquiree and the fair value of the acquirer’s previously held interest in the acquiree (if any), the excess is recognized immediately in profit or loss as a bargain purchase gain. Non-controlling interests that are present ownership interests and entitle their holders to a proportionate share of the entity’s net assets in the event of liquidation may be initially measured either at fair value or at the non-controlling interests’ proportionate share of the recognized amounts of the acquiree’s identifiable net assets. The choice of measurement is made on a transaction-by-transaction basis. Other types of non-controlling interests are measured at fair value. Where the consideration the Group transfers in a business combination includes assets or liabilities resulting from a contingent consideration arrangement, the contingent consideration is measured at its acquisition-date fair value and considered as part of the consideration transferred in a business combination. Changes in the fair value of the contingent consideration that qualify as measurement period adjustments are adjusted retrospectively, with the corresponding adjustments being made against goodwill or gains on bargain purchases. Measurement period adjustments are adjustments that arise from additional information obtained during the measurement period about facts and circumstances that existed as of the acquisition date. The measurement period does not exceed 1 year from the acquisition date. The subsequent accounting for changes in the fair value of the contingent consideration that do not qualify as measurement period adjustments depends on how the contingent consideration is classified. Contingent consideration not classified as equity is remeasured at fair value at the end of subsequent reporting period with any gain or loss recognized in profit or loss. When a business combination is achieved in stages, the Group’s previously held equity interest in an acquiree is remeasured to fair value at acquisition date, and the resulting gain or loss, if any, is recognized in profit or loss or other comprehensive income. Amounts arising from interests in the acquiree prior to the acquisition date that have previously been recognized in other comprehensive income are recognized on the same basis as would be required had those interest been directly disposed of by the Group. If the initial accounting for a business combination is incomplete by the end of the reporting period in which the combination occurs, the Group reports provisional amounts for the items for which the accounting is incomplete. Those provisional amounts are adjusted retrospectively during the measurement period, or additional assets or liabilities are recognized, to reflect new information obtained about facts and circumstances that existed at the acquisition date that, if known, would have affected the amounts recognized at that date. Business combination involving entities under common control is not accounted for using the acquisition method but is accounted for at the carrying amounts of the entities. The Group elected not to restate comparative information of the prior period in the financial statements as the business combination was an organization restructure under common control.
Foreign Currencies	f. Foreign currencies In preparing the financial statements of each individual entity, transactions in currencies other than the entity’s functional currency (i.e. foreign currencies) are recognized at the rates of exchange prevailing at the dates of the transactions. At each balance sheet date, monetary items denominated in foreign currencies are retranslated at the rates prevailing at that date. Exchange differences on monetary items arising from settlement or translation are recognized in profit or loss in the period in which they arise except for exchange differences on transactions entered into in order to hedge certain foreign currency risks. Non-monetary items denominated in foreign currencies that are measured at fair value are retranslated at the rates prevailing at the date when the fair value was determined. Exchange differences arising from the retranslation of non-monetary items are included in profit or loss for the period except for exchange differences arising from the retranslation of non-monetary items in respect of which gains and losses are recognized directly in other comprehensive income, in which cases, the exchange differences are also recognized directly in other comprehensive income. Non-monetary items denominated in a foreign currency and measured at historical cost are translated using the exchange rate at the date of the transaction, and are not retranslated. For the purposes of presenting the consolidated financial statements, the assets and liabilities of the Group’s foreign operations (including subsidiaries, associates and joint ventures in other countries that use currencies which are different from the currency of the Company) are translated into the New Taiwan dollars using exchange rates prevailing at each balance sheet date. Income and expense items are translated at the average exchange rates for the period. The resulting currency translation differences are recognized in other comprehensive income and accumulated in equity attributed to the owners of the Company and non-controlling interests as appropriate. On the disposal of the Group’s entire interest in a foreign operation, or a disposal involving the loss of control over a subsidiary that includes a foreign operation, or a partial disposal of an interest in a joint arrangement or an associate that includes a foreign operation of which the retained interest becomes a financial asset, all of the exchange differences accumulated in equity in respect of that operation attributable to the owners of the Company are reclassified to profit or loss. In relation to a partial disposal of a subsidiary that does not result in the Group losing control over the subsidiary, the proportionate share of accumulated exchange differences is re-attributed to the non-controlling interests of the subsidiary and is not recognized in profit or loss. For all other partial disposals, the proportionate share of the accumulated exchange differences recognized in other comprehensive income is reclassified to profit or loss. Goodwill and fair value adjustments recognized on identifiable assets and liabilities of acquired foreign operation are treated as assets and liabilities of the foreign operation and translated at the rates of exchange prevailing at the end of each reporting period. Exchange differences are recognized in other comprehensive income.
Inventories and Inventories Related to Real Estate Business	g. Inventories and inventories related to real estate business Inventories, including raw materials (materials received from customers for processing, mainly semiconductor wafers, are excluded from inventories as title and risk of loss remain with the customers), supplies, work in process, finished goods, and materials and supplies in transit are stated at the lower of cost or net realizable value. Inventory write-downs are made by item, except for those that may be appropriate to group items of similar or related inventories. Net realizable value is the estimated selling prices of inventories less all estimated costs of completion and estimated costs necessary to make the sale. Raw materials and supplies are recorded at moving average cost while work in process and finished goods are recorded at standard cost. Inventories related to real estate business include land and buildings held for sale, land held for construction and construction in progress. Land held for development is recorded as land held for construction upon obtaining the title of ownership. Prior to the completion, the borrowing costs directly attributable to construction in progress are capitalized as part of the cost of the asset. Construction in progress is transferred to land and buildings held for sale upon completion. Land and buildings held for sale, construction in progress and land held for construction are stated at the lower of cost or net realizable value and related write-downs are made by item. The amounts received in advance for real estate properties are first recorded as advance receipts and then recognized as revenue when the construction is completed and the title and significant risk of the real estate properties are transferred to customers. Cost of sales of land and buildings held for sale are recognized based on the ratio of property sold to the total property developed.
Investments in associates and joint ventures	h. Investments in associates and joint ventures An associate is an entity over which the Group has significant influence and that is neither a subsidiary nor an interest in a joint venture. Joint venture is a joint arrangement whereby the Group and other parties that have joint control of the arrangement have rights to the net assets of the arrangement. The Group applies the equity method to investments in an associate and joint venture. Under the equity method, investments in an associate and a joint venture are initially recognized at cost and adjusted thereafter to recognize the Group’s share of the profit or loss and other comprehensive income of the associate and joint venture. The Group also recognizes the changes in the Group’s share of equity of associates and joint venture. Any excess of the cost of acquisition over the Group’s share of the net fair value of the identifiable assets and liabilities of an associate or a joint venture at the date of acquisition is recognized as goodwill, which is included within the carrying amount of the investment and is not amortized. Any excess of the Group’s share of the net fair value of the identifiable assets and liabilities over the cost of acquisition after reassessment is recognized immediately in profit or loss. When the Group subscribes for additional new shares of an associate and joint venture at a percentage different from its existing ownership percentage, the resulting carrying amount of the investment differs from the amount of the Group’s proportionate interest in the associate and joint venture. The Group records such a difference as an adjustment to investments with the corresponding amount charged or credited to capital surplus - changes in capital surplus from investments in associates and joint ventures accounted for using the equity method. If the Group’s ownership interest is reduced due to its additional subscription of the new shares of the associate and joint venture, the proportionate amount of the gains or losses previously recognized in other comprehensive income in relation to that associate and joint venture is reclassified to profit or loss on the same basis as would be required had the investee directly disposed of the related assets or liabilities. When the adjustment should be debited to capital surplus, but the capital surplus recognized from investments accounted for using the equity method is insufficient, the shortage is debited to retained earnings. When the Group’s share of losses of an associate and a joint venture equals or exceeds its interest in that associate and joint venture (which includes any carrying amount of the investment accounted for using the equity method and long-term interests that, in substance, form part of the Group’s net investment in the associate and joint venture), the Group discontinues recognizing its share of further losses. Additional losses and liabilities are recognized only to the extent that the Group has incurred legal obligations or constructive obligations, or made payments on behalf of that associate and joint venture. The entire carrying amount of an investment (including goodwill) is tested for impairment as a single asset by comparing its recoverable amount with its carrying amount. Any impairment loss recognized is not allocated to any asset, including goodwill, that forms part of the carrying amount of the investment. Any reversal of that impairment loss is recognized to the extent that the recoverable amount of the investment subsequently increases. The Group discontinues the use of the equity method from the date on which its investment ceases to be an associate and a joint venture. Any retained investment is measured at fair value at that date, and the fair value is regarded as the investment’s fair value on initial recognition as a financial asset. The difference between the previous carrying amount of the associate and the joint venture attributable to the retained interest and its fair value is included in the determination of the gain or loss on disposal of the associate and the joint venture. The Group accounts for all amounts previously recognized in other comprehensive income in relation to that associate and joint venture on the same basis as would be required had that associate directly disposed of the related assets or liabilities. If an investment in an associate becomes an investment in a joint venture or an investment in a joint venture becomes an investment in an associate, the Group continues to apply the equity method and does not remeasure the retained interest. When a group entity transacts with its associate and joint venture, profits and losses resulting from the transactions with the associate and joint venture are recognized in the Group’ consolidated financial statements only to the extent that interests in the associate and the joint venture are not related to the Group.
Property, Plant and Equipment	i. Property, plant and equipment Except for land which is stated at cost, property, plant and equipment are stated at cost less accumulated depreciation and accumulated impairment. Properties in the course of construction are carried at cost, less any recognized impairment loss. Cost includes professional fees and borrowing costs eligible for capitalization. Such assets are depreciated and classified to the appropriate categories of property, plant and equipment when completed and ready for their intended use. Freehold land is not depreciated. Depreciation of property, plant and equipment is recognized using the straight-line method. Each significant part is depreciated separately. The estimated useful lives, residual values and depreciation method are reviewed at each balance sheet date, with the effect of any changes in estimate accounted for on a prospective basis. On derecognition of an item of property, plant and equipment, the difference between the sales proceeds and the carrying amount of the asset is recognized in profit or loss.
Investment Properties	j. Investment properties Investment properties are properties held to earn rental and/or for capital appreciation. Investment properties include right-of-use assets and properties under construction that meet the definition of investment properties. Freehold investment properties are initially measured at cost, including transaction costs. Subsequent to initial recognition, investment properties are measured at cost less accumulated depreciation and accumulated impairment loss. Investment properties acquired through leases are initially measured at cost, which comprises the initial measurement of lease liabilities adjusted for lease payments made on or before the commencement date, plus initial direct costs incurred and an estimate of costs needed to restore the underlying assets, less any lease incentives received. These investment properties are subsequently measured at cost less accumulated depreciation and accumulated impairment loss and adjusted for any remeasurement of the lease liabilities. Depreciation is recognized using the straight-line method. Investment properties under construction are measured at cost less accumulated impairment loss. Cost includes professional fees and borrowing costs eligible for capitalization. Depreciation of these assets commences when the assets are ready for their intended use. For a transfer of classification from investment properties to property, plant and equipment and to right-of-use assets, the deemed cost of the property for subsequent accounting is its carrying amount at the commencement of owner-occupation. For a transfer of classification from investment properties to inventories, the deemed cost of an item of property for subsequent accounting is its carrying amount at the commencement of development with a view to future sale. For a transfer of classification from property, plant and equipment and right-of-use assets to investment properties, the deemed cost of an item of property for subsequent accounting is its carrying amount at the end of owner-occupation. For a transfer of classification from inventories to investment properties, the deemed cost of an item of property for subsequent accounting is its carrying amount at the inception of an operating lease. On derecognition of an investment property, the difference between the net disposal proceeds and the carrying amount of the asset is included in profit or loss.
Goodwill	k. Goodwill Goodwill arising from an acquisition of a business is carried at cost as established at the date of acquisition of the business less accumulated impairment loss. For the purposes of impairment testing, goodwill is allocated to each of the Group’s cash-generating units or groups of cash-generating units (referred to as “cash-generating unit”) that is expected to benefit from the synergies of the combination. A cash-generating unit to which goodwill has been allocated is tested for impairment annually, or more frequently when there is an indication that the unit may be impaired, by comparing its carrying amount, including the attributed goodwill, with its recoverable amount. However, if the goodwill allocated to a cash-generating unit was acquired in a business combination during the current annual period, that unit shall be tested for impairment before the end of the current annual period. If the recoverable amount of the cash-generating unit is less than its carrying amount, the impairment loss is allocated first to reduce the carrying amount of any goodwill allocated to the unit and then pro rata to the other assets of the unit based on the carrying amount of each asset in the unit. Any impairment loss is recognized directly in profit or loss. An impairment loss recognized for goodwill is not reversed in subsequent periods.
Other Intangible Assets	l. Other intangible assets 1) Separate acquisition Other intangible assets with finite useful lives acquired separately are initially measured at cost and subsequently measured at cost less accumulated amortization and accumulated impairment loss. Other intangible assets are amortized using the straight-line method over their estimated useful lives. The estimated useful lives, residual values, and amortization methods are reviewed at each balance sheet date, with the effect of any changes in estimate being accounted for on a prospective basis. 2) Acquired through business combinations Other intangible assets acquired in a business combination and recognized separately from goodwill are initially recognized at their fair value at the acquisition date which is regarded as their cost. Subsequent to initial recognition, they are measured on the same basis as intangible assets that are acquired separately. 3) Derecognition On derecognition of an intangible asset, the difference between the net disposal proceeds and the carrying amount of the asset are recognized in profit or loss.
Impairment of Tangible and Intangible Assets Other than Goodwill	m. Impairment of property, plant and equipment, right-of-use asset and intangible assets other than goodwill At each balance sheet date or whenever events or changes in circumstances indicate that the carrying value may not be recoverable, the Group reviews the carrying amounts of its property, plant and equipment, right-of-use asset and intangible assets, excluding goodwill, to determine whether there is any indication that those assets have suffered an impairment loss. If any such indication exists, the recoverable amount of the asset is estimated in order to determine the extent of the impairment loss. When it is not possible to estimate the recoverable amount of an individual asset, the Group estimates the recoverable amount of the cash-generating unit to which the asset belongs. Corporate assets are allocated to the individual cash-generating units on a reasonable and consistent basis of allocation. The recoverable amount is the higher of fair value less costs to sell and value in use. If the recoverable amount of an asset or cash-generating unit is estimated to be less than its carrying amount, the carrying amount of the asset or cash-generating unit is reduced to its recoverable amount, with the resulting impairment loss recognized in profit or loss. When an impairment loss is subsequently reversed, the carrying amount of the asset or cash-generating unit is increased to the revised estimate of its recoverable amount, but only to the extent of the carrying amount that would have been determined had no impairment loss been recognized for the asset or cash-generating unit in prior years. A reversal of an impairment loss is recognized immediately in profit or loss.
Financial Instruments	n. Financial instruments Financial assets and financial liabilities are recognized when a group entity becomes a party to the contractual provisions of the instruments. Financial assets and financial liabilities are initially measured at fair value. Transaction costs that are directly attributable to the acquisition or issue of financial assets and financial liabilities (other than financial assets and financial liabilities at FVTPL) are added to or deducted from the fair value of the financial assets or financial liabilities, as appropriate, on initial recognition. Transaction costs directly attributable to the acquisition of financial assets or financial liabilities at fair value through profit or loss are recognized immediately in profit or loss. 1) Financial assets All regular way purchases or sales of financial assets are recognized and derecognized on a settlement date basis. a) Measurement categories Financial assets held by the Group are classified into the following categories: financial assets at FVTPL, financial assets at amortized cost and investments in debt instruments and equity instruments at FVTOCI. i. Financial asset at FVTPL Financial asset is classified as at FVTPL when the financial asset is mandatorily classified or it is designated as at FVTPL. The Group’s financial assets mandatorily classified as at FVTPL include investments in equity instruments which are not designated as at FVTOCI and debt instruments that do not meet the amortized cost criteria or the FVTOCI criteria. Financial assets at FVTPL are subsequently measured at fair value , Fair value is determined in the manner described in Note 34. ii. Financial assets at amortized cost Financial assets that meet the following conditions are subsequently measured at amortized cost: i) The financial asset is held within a business model whose objective is to hold financial assets in order to collect contractual cash flows; and ii) The contractual terms of the financial asset give rise on specified dates to cash flows that are solely payments of principal and interest on the principal amount outstanding. Subsequent to initial recognition, financial assets at amortized cost, including cash and cash equivalents, trade receivables at amortized cost, other receivables and other financial assets, are measured at amortized cost, which equals to gross carrying amount determined using the effective interest method less any impairment loss. Exchange differences are recognized in profit or loss. Interest income is calculated by applying the effective interest rate to the gross carrying amount of a financial asset, except for: i) Purchased or originated credit-impaired financial assets, for which interest income is calculated by applying the credit-adjusted effective interest rate to the amortized cost of the financial asset; and ii) Financial assets that are not credit-impaired on purchase or origination but have subsequently become credit-impaired, for which interest income is calculated by applying the effective interest rate to the amortized cost of such financial assets in subsequent reporting periods. A financial asset is credit impaired when one or more of the following events have occurred: i) Significant financial difficulty of the issuer or the borrower; ii) Breach of contract, such as a default; iii) It is becoming probable that the borrower will enter bankruptcy or undergo a financial reorganization; or iv) The disappearance of an active market for that financial asset because of financial difficulties. Cash equivalents include time deposits with original maturities within 3 months from the date of acquisition, which are highly liquid, readily convertible to a known amount of cash and are subject to an insignificant risk of changes in value. These cash equivalents are held for the purpose of meeting short-term cash commitments. iii. Investments in debt instruments at FVTOCI For the Group’s debt instruments that meet the following conditions are subsequently measured at FVTOCI: i) the debt instrument is held within a business model whose objective is achieved by both the collecting of contractual cash flows and the selling of the financial assets; and ii) the contractual terms of the debt instrument give rise on specified dates to cash flows that are solely payments of principal and interest on the principal amount outstanding. Investments in debt instruments at FVTOCI are subsequently measured at fair value. Changes in the carrying amounts of these debt instruments relating to changes in foreign currency exchange rates, interest income calculated using the effective interest method and impairment losses or reversals are recognized in profit or loss. Other changes in the carrying amount of these debt instruments are recognized in other comprehensive income and will be reclassified to profit or loss when the investment is disposed of. iv. Investments in equity instruments at FVTOCI On initial recognition, the Group make an irrevocable election to designate investments in equity instruments as at FVTOCI. Designation at FVTOCI is not permitted if the equity investment is held for trading or if it is contingent consideration recognized by an acquirer in a business combination. Investments in equity instruments at FVTOCI are subsequently measured at fair value with gains and losses arising from changes in fair value recognized in other comprehensive income and accumulated in other equity. The cumulative gain or loss will not be reclassified to profit or loss on disposal of the equity investments, instead, they will be transferred to retained earnings. Dividends on these investments in equity instruments are recognized in profit or loss when the Group’s right to receive the dividends is established, unless the dividends clearly represent a recovery of part of the cost of the investment. b) Impairment of financial assets and contract assets At each balance sheet date, the Group recognizes a loss allowance for expected credit losses on financial assets at amortized cost (including trade receivables and contract assets) and investments in debt instruments that are measured at FVTOCI as well as contract assets. The Group always recognizes lifetime Expected Credit Loss (“ECL”) for trade receivables and contract assets. For all other financial instruments, the Group recognizes lifetime ECL when there has been a significant increase in credit risk since initial recognition. If, on the other hand, the credit risk on the financial instrument has not increased significantly since initial recognition, the Group measures the loss allowance for that financial instrument at an amount equal to 12-month ECL. Expected credit losses reflect the weighted average of credit losses with the respective risks of a default occurring as the weights. Lifetime ECL represents the expected credit losses that will result from all possible default events over the expected life of a financial instrument. In contrast, 12-month ECL represents the portion of lifetime ECL that is expected to result from default events on a financial instrument that are possible within 12 months after the reporting date. The Group recognizes an impairment gain or loss in profit or loss for all financial instruments with a corresponding adjustment to their carrying amount through a loss allowance account, except for investments in debt instruments that are measured at FVTOCI, for which the loss allowance is recognized in other comprehensive income and does not reduce the carrying amount of the financial asset. c) Derecognition of financial assets The Group derecognizes a financial asset only when the contractual rights to the cash flows from the asset expire or when it transfers the financial asset and substantially all the risks and rewards of ownership of the asset to another entity. On derecognition of a financial asset at amortized cost in its entirety, the difference between the asset’s carrying amount and the sum of the consideration received and receivable is recognized in profit or loss. On derecognition of an investment in a debt instrument at FVTOCI, the difference between the asset’s carrying amount and the sum of the consideration received and receivable and the cumulative gain or loss which had been recognized in other comprehensive income is recognized in profit or loss. However, on derecognition of an investment in an equity instrument at FVTOCI, the difference between the asset’s carrying amount and the sum of the consideration received and receivable is recognized in profit or loss, and the cumulative gain or loss which had been recognized in other comprehensive income is transferred directly to retained earnings, without recycling through profit or loss. 2) Equity instruments Debt and equity instruments issued by a group entity are classified as either financial liabilities or as equity in accordance with the substance of the contractual arrangements and the definitions of a financial liability and an equity instrument. Equity instruments issued by a group entity are recognized at the proceeds received, net of direct issue costs. Repurchase of the Company’s own equity instruments is recognized in and deducted directly from equity. No gain or loss is recognized in profit or loss on the purchase, sale, issue or cancellation of the Company’s own equity instruments. 3) Financial liabilities a) Subsequent measurement Except the following situations, all financial liabilities are measured at amortized cost using the effective interest method: Financial liabilities are classified as at FVTPL when such financial liabilities are held for trading. Financial liabilities held for trading are stated at fair value, and any gains or losses on such financial liabilities are recognized in other gains or losses. b) Derecognition of financial liabilities The difference between the carrying amount of a financial liability derecognized and the consideration paid, including any non-cash assets transferred or liabilities assumed, is recognized in profit or loss. 4) Derivative financial instruments The Group enters into a variety of derivative financial instruments to manage its exposure to interest rate and foreign exchange rate risks, including forward exchange contracts and swap contracts. Derivatives are initially recognized at fair value at the date on which the derivative contracts are entered into and are subsequently remeasured to their fair value at the end of each reporting period. The resulting gain or loss is recognized in profit or loss immediately unless the derivative is designated and effective as a hedging instrument; in which event, the timing of the recognition in profit or loss depends on the nature of the hedging relationship. When the fair value of a derivative financial instrument is positive, the derivative is recognized as a financial asset; when the fair value of a derivative financial instrument is negative, the derivative is recognized as a financial liability. Derivatives embedded in hybrid contracts that contain financial asset hosts that is within the scope of IFRS 9 are not separated; instead, the classification is determined in accordance with the entire hybrid contract. Derivatives embedded in non-derivative host contracts that are not financial assets that is within the scope of IFRS 9 (e.g. financial liabilities) are treated as separate derivatives when they meet the definition of a derivative, their risks and characteristics are not closely related to those of the host contracts and the host contracts are not measured at FVTPL.
Hedge Accounting	o. Hedge accounting The Group designates certain hedging instruments, which include derivatives, embedded derivatives and non-derivatives in respect of foreign currency risk, as either fair value hedges or cash flow hedges or hedges of net investment in foreign operations. 1) Fair value hedges Gains or losses on hedging instruments that are designated and qualify as fair value hedges are recognized in profit or loss immediately, together with any changes in the fair value of the hedged asset or liability that are attributable to the hedged risk. The change in the fair value of the hedging instrument and the change in the hedged item attributable to the hedged risk are recognized in profit or loss in the line item relating to the hedged item. The Group discontinues hedge accounting only when the hedging relationship ceases to meet the qualifying criteria; for instance, when the hedging instrument expires or is sold, terminated or exercised. 2) Cash flow hedges The effective portion of gains or losses on hedging instruments that are designated and qualify as cash flow hedges is recognized in other comprehensive income. The gains or losses relating to the ineffective portion are recognized immediately in profit or loss. The associated gains or losses that were recognized in other comprehensive income are reclassified from equity to profit or loss as a reclassification adjustment in the line item relating to the hedged item in the same period when the hedged item affects profit or loss. If a hedge of a forecasted transaction subsequently results in the recognition of a non-financial asset or a non-financial liability, the associated gains and losses that were recognized in other comprehensive income are removed from equity and included in the initial cost of the non-financial asset or non-financial liability. The Group discontinues hedge accounting only when the hedging relationship cease to meet the qualifying criteria; for instance, when the hedging instrument expires or is sold, terminated, or exercised. The cumulative gain or loss on the hedging instrument that has been previously recognized in other comprehensive income from the period when the hedge was effective remains separately in equity until the forecast transaction occurs. When a forecast transaction is no longer expected to occur, the gain or loss accumulated in equity is recognized immediately in profit or loss. 3) Hedges of net investments in foreign operations Hedges of net investments in foreign operations are accounted for similarly to cash flow hedges. Any gains or losses on the hedging instrument relating to the effective portion of the hedge are recognized in other comprehensive income and accumulated under the heading of foreign currency translation reserve. The gains or losses relating to the ineffective portion are recognized immediately in profit or loss. The gains and losses on the hedging instrument relating to the effective portion of the hedge, which were accumulated in the foreign currency translation reserve, are reclassified to profit or loss on the disposal or partial disposal of a foreign operation.
Revenue Recognition	p. Revenue recognition The Group identifies the contracts with customers, allocates transaction prices to performance obligations and, when performance obligations are satisfied, recognizes revenues at fixed amounts as agreed in the contracts with taking estimated volume discounts into consideration. For contracts where the period between the date on which the Group transfers a promised good or service to a customer and the date on which the customer pays for that good or service is one year or less, the Group does not adjust the promised amount of consideration for the effects of a significant financing component. The Group’s duration of contracts with customers is expected to be one year or less, and the consideration from contracts with customers is included in transaction price and, therefore, can apply the practical expedient that not to disclose the performance obligations including (i) the aggregate amount of the transaction price allocated to the performance obligations that are not fully satisfied or have partially completed at the end of the reporting period, and (ii) the expected timing for recognition of revenue. The Group’s operating revenues include revenues from sale of goods and services as well as sale and leasing of real estate properties. When customers control goods while they are manufactured in progress, the Group measures the progress on the basis of costs incurred relative to the total expected costs as there is a direct relationship between the costs incurred and the progress of satisfying the performance obligations. Revenue and contract assets are recognized during manufacture and contract assets are reclassified to trade receivables when the manufacture is completed or when the goods are shipped upon customer’s request. The Group recognizes revenues and trade receivables when the goods are shipped or when the goods are delivered to the customer’s specific location because it is the time when the customer has full discretion over the manner of distribution and price to sell the goods, has the primary responsibility for sales to future customers and bears the risks of obsolescence. Revenues from sale of real estate properties are recognized when customers purchase real estate properties and complete the transfer procedures. Revenues from leasing real estate properties are recognized during leasing periods on the straight-line basis.
Leasing	q. Leases At the inception of a contract, the Group assesses whether the contract is, or contains, a lease. For a contract that contains a lease component and non-lease components, the Group elects to account for the lease and non-lease components as a single lease component. 1) The Group as lessor Leases are classified as finance leases whenever the terms of a lease transfer substantially all the risks and rewards of ownership to the lessee. All other leases are classified as operating leases. When the Group subleases a right-of-use asset, the sublease is classified by reference to the right-of-use asset arising from the head lease, not with reference to the underlying asset. However, if the head lease is a short-term lease that the Group, as a lessee, has accounted for applying recognition exemption, the sublease is classified as an operating lease. Lease payments (less any lease incentives payable) from operating leases are recognized as income on a straight-line basis over the terms of the relevant leases. Initial direct costs incurred in obtaining operating leases are added to the carrying amounts of the underlying assets and recognized as expenses on a straight-line basis over the lease terms. 2) The Group as lessee The Group recognizes right-of-use assets and lease liabilities for all leases at the commencement date of a lease, except for short-term leases and low-value asset leases accounted for applying a recognition exemption where lease payments are recognized as expenses on a straight-line basis over the lease terms. Right-of-use assets are initially measured at cost, which comprises the initial measurement of lease liabilities adjusted for lease payments made on or before the commencement date, plus any initial direct costs incurred and an estimate of costs needed to restore the underlying assets, and less any lease incentives received. Right-of-use assets are subsequently measured at cost less accumulated depreciation and impairment losses and adjusted for any remeasurement of the lease liabilities. Right-of-use assets are presented on a separate line in the consolidated balance sheets. With respect to the recognition and measurement of right-of-use assets that meet the definition of investment properties, refer to the aforementioned accounting policies for investment properties. Right-of-use assets are depreciated using the straight-line method from the commencement dates to the earlier of the end of the useful lives of the right-of-use assets or the end of the lease terms. However, if leases transfer ownership of the underlying assets to the Group by the end of the lease terms or if the costs of right-of-use assets reflect that the Group will exercise a purchase option, the Group depreciates the right-of-use assets from the commencement dates to the end of the useful lives of the underlying assets. Lease liabilities are initially measured at the present value of the lease payments, which comprise fixed payments, in-substance fixed payments, variable lease payments which depend on an index or a rate, residual value guarantees, the exercise price of a purchase option if the Group is reasonably certain to exercise that option, and payments of penalties for terminating a lease if the lease term reflects such termination, less any lease incentives receivable. The lease payments are discounted using the interest rate implicit in a lease, if that rate can be readily determined. If that rate cannot be readily determined, the Group uses the lessee’s incremental borrowing rate. Subsequently, lease liabilities are measured at amortized cost using the effective interest method, with interest expense recognized over the lease terms. When there is a change in a lease term, a change in the amounts expected to be payable under a residual value guarantee, a change in the assessment of an option to purchase an underlying asset, or a change in future lease payments resulting from a change in an index or a rate used to determine those payments, the Group remeasures the lease liabilities with a corresponding adjustment to the right-of-use assets. However, if the carrying amount of the right-of-use assets is reduced to zero, any remaining amount of the remeasurement is recognized in profit or loss. For a lease modification that is not accounted for as a separate lease, the Group accounts for the remeasurement of the lease liability by (a) decreasing the carrying amount of the right-of-use asset of lease modifications that decreased the scope of the lease, and recognizing in profit or loss any gain or loss on the partial or full termination of the lease; (b) making a corresponding adjustment to the right-of-use asset of all other lease modifications. Lease liabilities are presented on a separate line in the consolidated balance sheets. The Group negotiates with the lessor for rent concessions as a direct consequence of the COVID-19 to change the lease payments originally due by June 30, 2021, that results in the revised consideration for the lease substantially less than the consideration for the lease immediately preceding the change. There is no substantive change to other terms and conditions. The Group elects to apply the practical expedient to all of these rent concessions, and therefore, does not assess whether the rent concessions are lease modifications. Instead, the Group recognizes the reduction in lease payment in profit or loss as a deduction of expenses of variable lease payments, in the period in which the events or conditions that trigger the concession occurs, and makes a corresponding adjustment to the lease liability. Variable lease payments that do not depend on an index or a rate are recognized as expenses in the periods in which they are incurred.
Borrowing Costs	r. Borrowing costs Borrowing costs directly attributable to the acquisition, construction or production of qualifying assets are added to the cost of those assets, until such time as the assets are substantially ready for their intended use or sale. Investment income earned on the temporary investment of specific borrowings pending their expenditure on qualifying assets is deducted from the borrowing costs eligible for capitalization. Other than stated above, all other borrowing costs are recognized in profit or loss in the period in which they are incurred.
Government grants	s. Government grants Government grants related to income are not recognized until there is reasonable assurance that the Group will comply with the conditions attaching to them and that the grants will be received. Government grants are recognized in other income on a systematic basis over the periods in which the Group recognizes as expenses the related costs for which the grants are intended to compensate. Specifically, government grants whose primary condition is that the Group should purchase, construct or otherwise acquire non-current assets are recognized as deferred revenue in the consolidated financial statements and transferred to profit or loss on a systematic and rational basis over the useful lives of the related assets. Government grants that are receivable as compensation for expenses or losses already incurred or for the purpose of giving immediate financial support to the Group with no future related costs are recognized in profit or loss in the period in which they become receivable. The loan with interest subsidy provided by goevernment, bearing a below-market rate of interest is treated as a government grant measured as the difference between the proceeds received and the fair value of the loan based on prevailing market interest rates.
Employee Benefits	t. Employee benefits 1) Short-term employee benefits Liabilities recognized in respect of short-term employee benefits are measured at the undiscounted amount of the benefits expected to be paid in exchange for the related services. 2) Retirement benefits Payments to defined contribution retirement benefit plans are recognized as expenses when employees have rendered services entitling them to the contributions. Defined benefit costs (including service cost, net interest and remeasurement) under the defined benefit retirement benefit plans are determined using the projected unit credit method. Service cost (including current service cost and past service cost) and net interest on the net defined benefit liability (asset) are recognized as employee benefits expense in the period they occur. Remeasurement, comprising actuarial gains and losses and the return on plan assets (excluding interest), is recognized in other comprehensive income in the period in which they occur. Remeasurement recognized in other comprehensive income is reflected immediately in retained earnings and will not be reclassified to profit or loss. Net defined benefit liability (asset) represents the actual deficit (surplus) in the Group’s defined benefit plan. Any surplus resulting from this calculation is limited to the present value of any refunds from the plans or reductions in future contributions to the plans.
Employee share options	u. Share-based payment arrangements The fair value at the grant date of the employee share options and restricted shares for employees is expensed on a straight-line basis over the vesting period, based on the Group’s best estimate of the number of options or shares that are expected to ultimately vest, with a corresponding increase in capital surplus - employee share options and non-controlling interests. It is recognized as an expense in full at the grant date if vesting immediately. The grant date of issued ordinary shares for cash which are reserved for employees is the date on which the number of shares that the employees purchase is confirmed. At each balance sheet date, the Group reviews its estimate of the number of employee share options and restricted shares for employees expected to vest. The impact of the revision of the original estimates is recognized in profit or loss such that the cumulative expense reflects the revised estimate, with a corresponding adjustment to the capital surplus - employee share options and non-controlling interests.
Taxation	v. Taxation Income tax expense represents the sum of the tax currently payable and deferred tax. 1) Current tax Income tax payable (recoverable) is based on taxable profit (loss) for the year determined according to the applicable tax laws of each tax jurisdiction. According to the Income Tax Law of the R.O.C., an additional tax of unappropriated earnings is provided for in the year the shareholders approve to retain earnings. Adjustments of prior years’ tax liabilities are added to or deducted from the current year’s tax provision. 2) Deferred tax Deferred tax is recognized on temporary differences between the carrying amounts of assets and liabilities in the consolidated financial statements and the corresponding tax bases used in the computation of taxable profit. If a temporary difference arises from the initial recognition (other than in a business combination) of assets and liabilities in a transaction that affects neither the taxable profit nor the accounting profit, the resulting deferred tax asset or liability is not recognized. In addition, a deferred tax liability is not recognized on taxable temporary differences arising from the initial recognition of goodwill. Deferred tax liabilities are generally recognized for all taxable temporary differences. Deferred tax assets are generally recognized for all deductible temporary differences, unused loss carryforwards and unused tax credits for purchases of machinery and equipment to the extent that it is probable that taxable profits will be available against which those deductible temporary differences can be utilized. Deferred tax liabilities are recognized for taxable temporary differences associated with investments in subsidiaries and associates, except where the Group is able to control the reversal of the temporary differences and it is probable that the temporary difference will not reverse in the foreseeable future. Deferred tax assets arising from deductible temporary difference associated with such investments and interests are only recognized to the extent that it is probable that there will be sufficient taxable profits against which to utilize the benefits of the temporary differences and they are expected to reverse in the foreseeable future. The carrying amount of deferred tax assets is reviewed at each balance sheet date and reduced to the extent that it is no longer probable that sufficient taxable profits will be available to allow all or part of the assets to be recovered. A previously unrecognized deferred tax asset is also reviewed at each balance sheet date and recognized to the extent that it has become probable that future taxable profit will allow the deferred tax asset to be recovered. Deferred tax liabilities and assets are measured at the tax rates that are expected to apply in the period in which the liabilities are settled or assets are realized, based on tax rates (and tax laws) that have been enacted or substantively enacted by the balance sheet date. The measurement of deferred tax liabilities and assets reflects the tax consequences that would follow from the manner in which the Group expects, at the balance sheet date, to recover or settle the carrying amount of its assets and liabilities. 3) Current and deferred tax for the year Current and deferred tax are recognized in profit or loss, except when they relate to items that are recognized in other comprehensive income or directly in equity, in which case, the current and deferred tax are also recognized in other comprehensive income or directly in equity, respectively. Where current tax or deferred tax arises from the initial accounting for a business combination, the tax effect is included in the accounting for the business combination.
U.S. Dollar Amounts	w. U.S. Dollar Amounts A translation of the consolidated financial statements into U.S. dollars is included solely for the convenience of the readers, and has been translated from New Taiwan dollar (NT$) at the exchange rate as set forth in the statistical release by the U.S. Federal Reserve Board of the United States, which was NT$28.08 to US$1.00 as of December 31, 2020. The translation should not be construed as a representation that the NT$ amounts have been, could have been, or could in the future be, converted into U.S. dollars at this or any other rate of exchange.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2020
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Summary of Subsidiaries	2) Subsidiaries included in consolidated financial statements were as follows: Establishment Percentage of Ownership (%) and Operating December December Name of Investor Name of Investee Main Businesses Location 31, 2019 31, 2020 The Company ASE Engaged in the packaging and testing of semiconductors R.O.C. 100.0 100.0 USI Inc. (“USIINC”) Holding company R.O.C. 100.0 100.0 SPIL Engaged in the assembly, testing and turnkey services of integrated circuit R.O.C. 100.0 100.0 ASE A.S.E. Holding Limited Holding company Bermuda 100.0 100.0 J & R Holding Limited (“J&R Holding”) Holding company Bermuda 100.0 100.0 Innosource Limited Holding company British Virgin Islands 100.0 100.0 Omniquest Industrial Limited Holding company British Virgin Islands 71.0 71.0 ASE Marketing & Service Japan Co., Ltd. Engaged in marketing and sales services Japan 100.0 100.0 ASE Test, Inc. Engaged in the testing of semiconductors R.O.C. 100.0 100.0 Luchu Development Corporation Engaged in the development of real estate properties R.O.C. 67.1 67.1 ASE Embedded Electronics Inc. (“ASEEE”) Merged into ASE in February 2020 R.O.C. 100.0 - Advanced Microelectronic Products Inc. (“AMPI”) Engaged in the manufacturing of integrated circuit R.O.C. 7.6 7.6 ASE Test, Inc. Alto Enterprises Limited Holding company British Virgin Islands 100.0 100.0 Super Zone Holdings Limited Holding company Hong Kong 100.0 100.0 Luchu Development Corporation Engaged in the development of real estate properties R.O.C. 19.0 19.0 TLJ Intertech Inc. Engaged in information software services R.O.C. 60.0 60.0 MingFeng Information Service Corp., Ltd. Engaged in information software services R.O.C. 100.0 100.0 AMPI Engaged in the manufacturing of integrated circuit R.O.C. 43.4 43.4 A.S.E. Holding Limited ASE Investment (Labuan) Inc. Holding company Malaysia 70.1 70.1 ASE Test Limited (“ASE Test”) Holding company Singapore 10.2 10.2 J&R Holding ASE Test Holding company Singapore 89.8 89.8 Omniquest Industrial Limited Holding company British Virgin Islands 8.4 8.4 J&R Industrial Inc. Engaged in leasing equipment and investing activity R.O.C. 100.0 100.0 ASE Japan Co., Ltd. (“ASE Japan”) Engaged in the packaging and testing of semiconductors Japan 100.0 100.0 ASE (U.S.) Inc. After-sales service and sales support U.S.A. 100.0 100.0 Global Advanced Packaging Technology Limited Holding company British Cayman Islands 100.0 100.0 Anstock Limited Engaged in financing activity British Cayman Islands 100.0 100.0 Anstock II Limited Engaged in financing activity British Cayman Islands 100.0 100.0 Suzhou ASEN Semiconductors Co., Ltd. (“ASEN”) Engaged in the packaging and testing of semiconductors Suzhou, China 100.0 100.0 Innosource Limited Omniquest Industrial Limited Holding company British Virgin Islands 20.6 20.6 ASE (Shanghai) Inc. Engaged in the production of substrates Shanghai, China 8.5 8.5 Omniquest Industrial Limited ASE Corporation Holding company British Cayman Islands 100.0 100.0 Alto Enterprises Limited ASE (Kunshan) Inc. Engaged in the packaging and testing of semiconductors Kun Shan, China 22.9 22.9 ASE Investment (Kun Shan) Limited Holding company Kun Shan, China 85.9 85.9 Super Zone Holdings Limited Advanced Semiconductor Engineering (China) Ltd. Engaged in the packaging and testing of semiconductors Shanghai, China 100.0 100.0 ASE Investment (Labuan) Inc. ASE (Korea) Inc. (“ASE Korea”) Engaged in the packaging and testing of semiconductors Korea 100.0 100.0 ASE Korea ASE WeiHai Inc. Engaged in the packaging and testing of semiconductors Shandong, China 100.0 100.0 ASE Test ASE Test Holdings, Ltd. Holding company British Cayman Islands 100.0 100.0 ASE Holdings (Singapore) Pte Ltd Holding company Singapore 100.0 100.0 ASE Investment (Labuan) Inc. Holding company Malaysia 29.9 29.9 ASE Singapore Pte. Ltd. Engaged in the packaging and testing of semiconductors Singapore 100.0 100.0 ASE Test Holdings, Ltd. ISE Labs, Inc. Engaged in the testing of semiconductors U.S.A. 100.0 100.0 (Continued) Establishment Percentage of Ownership (%) and Operating December December Name of Investor Name of Investee Main Businesses Location 31, 2019 31, 2020 ISE Labs, Inc. ISE Services, Inc. Engaged in wafer procurement and customer product management services and commenced operations in February 2020 U.S.A. - 100.0 ASE Holdings (Singapore) Pte Ltd ASE Electronics (M) Sdn. Bhd. Engaged in the packaging and testing of semiconductors Malaysia 100.0 100.0 Global Advanced Packaging Technology Limited ASE Assembly & Test (Shanghai) Limited (“ASESH”) Engaged in the packaging and testing of semiconductors Shanghai, China 100.0 100.0 ASE Advanced Semiconductor (Shanghai) Limited Engaged in the packaging and testing of semiconductors and was established and spun off from ASESH in November 2020 Shanghai, China - 100.0 ASESH ASE Investment (Kun Shan) Limited Holding company Kun Shan, China 14.1 14.1 Wuxi Tongzhi Microelectronics Co., Ltd. Engaged in the packaging and testing of semiconductors Wuxi, China 100.0 100.0 ISE Labs, China, Ltd. Engaged in the testing of semiconductor Shanghai, China 100.0 100.0 Shanghai Ding Hui Real Estate Development Co., Ltd. (“DH”) Engaged in the development, construction and sale of real estate properties Shanghai, China 60.0 60.0 DH Shanghai Ding Qi Property Management Co., Ltd. Engaged in the management of real estate properties Shanghai, China 100.0 100.0 Shanghai Ding Wei Real Estate Development Co., Ltd. (“DW”) Engaged in the development, construction and leasing of real estate properties Shanghai, China 100.0 100.0 Shanghai Ding Yu Real Estate Development Co., Ltd. Engaged in the development, construction and leasing of real estate properties Shanghai, China 100.0 100.0 Kun Shan Ding Hong Real Estate Development Co., Ltd Engaged in the development, construction and leasing of real estate properties Kun Shan, China 100.0 100.0 Shanghai Ding Xu Property Management Co., Ltd. Engaged in the management of real estate properties Shanghai, China 100.0 100.0 Shanghai Dingyao Estate Development Co., Ltd. Engaged in property management and was invested in April 2020 Shanghai, China - 100.0 Shanghai Ding Fan Business Management Co., Ltd. (The name was changed on June 2020 and the former name was Shanghai Ding Fan Department Store Co., Ltd.) Engaged in the management of real estate properties (acquired from DW in November 2020) Shanghai, China - 100.0 DW Shanghai Ding Fan Business Management Co., Ltd. (The name was changed on June 2020 and the former name was Shanghai Ding Fan Department Store Co., Ltd.) Engaged in leasing and management of real estate properties (disposed to DH in November 2020) Shanghai, China 100.0 - ASE Investment (Kun Shan) Limited ASE (Kunshan) Inc. Engaged in the packaging and testing of semiconductors Kun Shan, China 49.3 49.3 ASE Corporation ASE Mauritius Inc. Holding company Mauritius 100.0 100.0 ASE Labuan Inc. Holding company Malaysia 100.0 100.0 ASE Mauritius Inc. ASE (Kunshan) Inc. Engaged in the packaging and testing of semiconductors Kun Shan, China 27.8 27.8 ASE (Shanghai) Inc. Engaged in the production of substrates Shanghai, China 91.5 91.5 ASE Labuan Inc. ASE Electronics Inc. Engaged in the production of substrates R.O.C. 100.0 100.0 ASE (Shanghai) Inc. Advanced Semiconductor Engineering (HK) Limited Engaged in the trading of substrates Hong Kong 100.0 100.0 Shanghai Ding Hui Real Estate Development Co., Ltd. Engaged in the development, construction and sale of real estate properties Shanghai, China 40.0 40.0 Universal Scientific Industrial (Shanghai) Co., Ltd. (“USISH”) Engaged in the designing, manufacturing and sales of electronic components Shanghai, China 0.8 0.8 USIINC Huntington Holdings International Co., Ltd. Holding company British Virgin Islands 100.0 100.0 Huntington Holdings International Co., Ltd. Unitech Holdings International Co., Ltd. Holding company British Virgin Islands 100.0 100.0 Real Tech Holdings Limited Holding company British Virgin Islands 100.0 100.0 Universal ABIT Holding Co., Ltd. In the process of liquidation British Cayman Islands 100.0 100.0 Real Tech Holdings Limited Universal Scientific Industrial (Kunshan) Co., Ltd. Liquidated in June 2020 Kun Shan, China 100.0 - USI Enterprise Limited (“USIE”) Engaged in the service of investment advisory and warehousing management Hong Kong 95.8 95.9 USIE USISH Engaged in the designing, manufacturing and sales of electronic components Shanghai, China 77.7 76.6 USISH Universal Global Technology Co., Limited Holding company Hong Kong 100.0 100.0 Establishment Percentage of Ownership (%) and Operating December December Name of Investor Name of Investee Main Businesses Location 31, 2019 31, 2020 Universal Global Technology (Kunshan) Co., Ltd. (“UGKS”) Engaged in the designing and manufacturing of electronic components Kun Shan, China 100.0 100.0 Universal Global Technology (Shanghai) Co., Ltd. Engaged in the processing and sales of computer and communication peripherals as well as business in import and export of goods and technology Shanghai, China 100.0 100.0 Universal Global Electronics (Shanghai) Co., Ltd. Engaged in the sales of electronic components and telecommunications equipment Shanghai, China 100.0 100.0 USI Electronics (Shenzhen) Co., Ltd. Engaged in the design, manufacturing and sales of motherboards and computer peripherals Shenzhen, China 50.0 50.0 Huanrong Electronics (Huizhou) Co., Ltd. Engaged in the research and manufacturing of new electronic applications, communications, computers and other electronics products and also provided auxiliary technical services as well as import and export services (acquired from Universal Global Electronics (Shanghai) Co., Ltd. in November 2020) Huizhou, China - 100.0 FINANCIERE AFG (“ ） Holding company France - 10.4 Universal Global Technology Co., Limited Universal Global Industrial Co., Limited Engaged in manufacturing, trading and investing activity Hong Kong 100.0 100.0 Universal Global Scientific Industrial Co., Ltd. (“UGTW”) Engaged in the manufacturing of components of telecomm and cars and provision of related R&D services R.O.C. 100.0 100.0 USI America Inc. Engaged in the manufacturing and processing of motherboards and wireless network communication and provision of related technical service U.S.A. 100.0 100.0 Universal Scientific Industrial De Mexico S.A. De C.V. Engaged in the assembling of motherboards and computer components Mexico 100.0 100.0 USI Japan Co., Ltd. Engaged in the manufacturing and sales of computer peripherals, integrated chip and other related accessories Japan 100.0 100.0 USI Electronics (Shenzhen) Co., Ltd. Engaged in the design, manufacturing and sales of motherboards and computer peripherals Shenzhen, China 50.0 50.0 Universal Global Electronics Co., Ltd. Engaged in accepting and outsourcing orders as well as sales of electronic components and service of technical advisory Hong Kong 100.0 100.0 Universal Scientific Industrial (France) (“USIFR”) Engaged in investing activities and was established in August 2019 France 100.0 100.0 Universal Scientific Industrial Vietnam Company Limited Engaged in IC assembly for wearable devices and was established in July 2020. Vietnam - 100.0 Universal Global Industrial Co., Limited Universal Scientific Industrial De Mexico S.A. De C.V. Engaged in the assembling of motherboards and computer components Mexico (Note) (Note) UGTW Universal Scientific Industrial Co., Ltd. (“USI”) Engaged in the manufacturing, processing and sales of computers, computer peripherals and related accessories R.O.C. 100.0 100.0 USI Electronics (Shenzhen) Co., Ltd. Huanrong Electronics (Huizhou) Co., Ltd. Engaged in the research and manufacturing of new electronic applications, communications, computers and other electronics products and also provided auxiliary technical services as well as import and export services (disposed to USISH in November 2020) Huizhou, China 100.0 - Universal Global Electronics Co., Ltd. Semicondutores Avancados do Brasil S.A. Liquidated in December 2020 Brasil 75.0 - Universal Scientific Industrial Poland Sp. z o.o. (“USIPL”) (The name was changed on June 2020 and the former name was Chung Hong Electronics Poland Sp. z o.o.) Engaged in the design and manufacturing of electronic components and new electronic applications Poland 60.0 100.0 Universal Global Electronics (Shanghai) Co., Ltd. USI Science and Technology (Shenzhen) Co., Ltd. Engaged in the design of electronic components, service of technical advisory; wholesale of electronic components and communication peripherals as well as business in import and export of goods and management of properties and was established in November 2020. Shenzhen, China - 100.0 USIFR FAFG Holding company France - 89.6 ASTEELFLASH GROUP Holding company France - (Note) Establishment Percentage of Ownership (%) and Operating December December Name of Investor Name of Investee Main Businesses Location 31, 2019 31, 2020 FAFG ASTEELFLASH GROUP Holding company France - 100.0 MANUFACTURING POWER TUNISIA Engaged in the design and manufacturing of electronic components Tunisia 0.1 ASTEELFLASH MEXICO S.A. de C.V. Engaged in the design and manufacturing of electronic components Mexico 0.1 ASTEELFLASH GROUP ASTEELFLASH (BEDFORD) LIMITED Engaged in the design and manufacturing of electronic components United Kingdom - 100.0 ASTEELFLASH FRANCE Engaged in the design and manufacturing of electronic components France - 99.9 ASTEELFLASH TUNISIE S.A. Engaged in the design and manufacturing of electronic components Tunisia - 100.0 ASTEELFLASH HONG KONG LIMITED Holding company Hong Kong - 100.0 ASTEELFLASH MEXICO S.A. de C.V. Engaged in the design and manufacturing of electronic components Mexico - 99.9 ASTEELFLASH GERMANY GmbH Engaged in the design and manufacturing of electronic components Germany - 100.0 MANUFACTURING POWER TUNISIA Engaged in the design and manufacturing of electronic components Tunisia - 99.9 ASTEELFLASH US HOLDING CORP. Holding company U.S.A. - 100.0 ASTEEL ELECTRONIQUE FOUCHANA Engaged in the design and manufacturing of electronic components Tunisia - (Note) AFERH TUNISIE Engaged in the management, training and consulting of human resources Tunisia - 0.5 ASTEEL ELECTRONICS MANUFACTURING SERVICES Engaged in the design and manufacturing of electronic components Tunisia 0.1 ASTEELFLASH (BEDFORD) LIMITED ASTEELFLASH TUNISIE S.A. Engaged in the design and manufacturing of electronic components Tunisia - (Note) ASTEELFLASH TECHNOLOGIE ASTEELFLASH FRANCE Engaged in the design and manufacturing of electronic components France - (Note) ASTEELFLASH FRANCE SCI CHASSET Engaged in the management and operation of real estate properties and holding the ownership of real estate properties France - 100.0 AFERH Engaged in the management, training and consulting of human resources France - 100.0 ASTEEL ELECTRONICS MANUFACTURING SERVICES Engaged in the design and manufacturing of electronic components Tunisia - 99.9 ASTEEL ELECTRONIQUE FOUCHANA Engaged in the design and manufacturing of electronic components Tunisia - 94.2 ASTEELFLASH TECHNOLOGIE Engaged in projection of plastic and the design and manufacturing of industrial components France - 100.0 ASTEELFLASH BRETAGNE Engaged in the design and manufacturing of electronic components France - 100.0 ASTEELFLASH TUNISIE S.A. Engaged in the design and manufacturing of electronic components Tunisia - (Note) ASTEELFLASH TUNISIE S.A. ASTEEL ELECTRONIQUE TUNISIE Engaged in the design and manufacturing of electronic components Tunisia - 100.0 ASTEEL ELECTRONIQUE FOUCHANA Engaged in the design and manufacturing of electronic components Tunisia (Note) AFERH AFERH TUNISIE Engaged in the management, training and consulting of human resources Tunisia - 99.5 ASTEELFLASH HONG KONG LIMITED ASTEELFLASH SUZHOU CO., LTD. Engaged in the design and manufacturing of electronic components Suzhou, China - 100.0 ASTEELFLASH SUZHOU CO., LTD. ASTEEL ELECTRONIQUE FOUCHANA Engaged in the design and manufacturing of electronic components Tunisia - (Note) ASTEELFLASH TUNISIE S.A. Engaged in the design and manufacturing of electronic components Tunisia - (Note) ASTEELFLASH GERMANY GmbH ASTEELFLASH HERSFELD GmbH Engaged in the design and manufacturing of electronic components Germany - 100.0 ASTEELFLASH EBERBACH GmbH Engaged in the design and manufacturing of electronic components Germany - 100.0 ASTEELFLASH BONN GmbH Engaged in the design and manufacturing of electronic components Germany - 100.0 ASTEELFLASH SCHWANDORF GmbH Engaged in the design and manufacturing of electronic components Germany - 100.0 ASTEELFLASH PLZEN S.R.O. Engaged in the design and manufacturing of electronic components Czech Republic - 100.0 ASTEELFLASH DESIGN SOLUTIONS HAMBOURG GmbH Engaged in the design and manufacturing of electronic components Germany - 100.0 EN ELECTRONICNETWORK SRL Engaged in the design and manufacturing of electronic components Romania - 100.0 Establishment Percentage of Ownership (%) and Operating December December Name of Investor Name of Investee Main Businesses Location 31, 2019 31, 2020 ASTEELFLASH TUNISIE S.A. Engaged in the design and manufacturing of electronic components Tunisia - (Note) ASTEELFLASH MEXICO S.A. de C.V. ASTEELFLASH TUNISIE S.A. Engaged in the design and manufacturing of electronic components Tunisia - (Note) ASTEELFLASH US HOLDING CORP. ASTEELFLASH USA CORP. Engaged in the design and manufacturing of electronic components U.S.A. - 100.0 ASTEELFLASH USA CORP. ASTEEL ELECTRONIQUE FOUCHANA Engaged in the design and manufacturing of electronic components Tunisia - (Note) ASTEELFLASH TUNISIE S.A. Engaged in the design and manufacturing of electronic components Tunisia - (Note) SPIL SPIL (B.V.I.) Holding Limited Engaged in investing activities British Virgin Islands 100.0 100.0 Siliconware Investment Co., Ltd. Engaged in investing activities R.O.C. 100.0 100.0 SPIL (B.V.I.) Holding Limited Siliconware USA, Inc. Engaged in marketing activities U.S.A. 100.0 100.0 SPIL (Cayman) Holding Limited Engaged in investing activities British Cayman Islands 100.0 100.0 SPIL (Cayman) Holding Limited Siliconware Technology (Suzhou) Limited (“SZ”) Engaged in the packaging and testing of semiconductors Suzhou, China 100.0 100.0 Siliconware Electronics (Fujian) Co., Limited (“SF”) Engaged in the packaging and testing of semiconductors and was disposed in October 2020 (Note 30) Fujian, China 100.0 - (Concluded)

Cash and Cash Equivalents (Tabl

Cash and Cash Equivalents (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Cash and Cash Equivalents	December 31 2019 2020 NT$ NT$ US$ (Note 4) Cash on hand $ 6,567 $ 6,073 $ 216 Checking accounts and demand deposits 44,565,936 48,734,866 1,735,572 Cash equivalents Cash equivalents (time deposits with original maturity of less than three months) 15,558,372 2,797,132 99,613 $ 60,130,875 $ 51,538,071 $ 1,835,401

Financial Instruments at Fair_2

Financial Instruments at Fair Value Through Profit or Loss (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Financial Instruments at Fair Value Through Profit or Loss	December 31 2019 2020 NT$ NT$ US$ (Note 4) Financial assets mandatorily classified as at FVTPL Derivative instruments (non-designated hedges) Forward exchange contracts $ 104,308 $ 122,511 $ 4,363 Swap contracts 56,561 99,312 3,537 Call option (Note 29) 24,556 - - Non-derivative financial assets Quoted ordinary shares $ 3,460,123 $ 4,064,438 $ 144,745 Private-placement funds 603,718 1,124,754 40,055 Unquoted preferred shares 377,440 385,440 13,726 Open-end mutual funds 662,290 339,338 12,085 5,288,996 6,135,793 218,511 Current 4,127,566 4,342,605 154,651 Non-current $ 1,161,430 $ 1,793,188 $ 63,860 Financial liabilities held for trading - current Derivative instruments (non-designated hedging) Swap contracts $ 862,581 $ 1,448,972 $ 51,602 Target redemption forward contracts - 79,216 2,821 Forward exchange contracts 110,990 9,020 321 $ 973,571 $ 1,537,208 $ 54,744
Summary of Outstanding Contracts Not Accounted for Hedge Accounting	At each balance sheet date, outstanding s Notional Amount Currency Maturity Period (In Thousands) December 31, 2019 Sell NT$/Buy US$ 2020.01-2020.12 NT$50,241,799/US$1,660,000 Sell US$/Buy RMB 2020.02 US$49,666/RMB349,800 Sell US$/Buy JPY 2020.02-2020.03 US$45,878/JPY5,000,000 Sell US$/Buy KRW 2020.01 US$28,000/KRW32,454,800 Sell US$/Buy MYR 2020.01 US$11,000/MYR45,507 Sell US$/Buy NT$ 2020.01 US$189,960/NT$5,719,478 December 31, 2020 Sell NT$/Buy US$ 2021.01-2021.12 NT$51,140,082/US$1,755,000 Sell US$/Buy RMB 2021.01-2021.02 US$59,793/RMB395,742 Sell US$/Buy HKD 2021.02 US$13,804/HKD107,000 Sell US$/Buy JPY 2021.01 US$41,630/JPY4,300,000 Sell US$/Buy KRW 2021.01 US$30,000/KRW33,066,000 Sell US$/Buy NT$ 2021.01-2021.02 US$675,240/NT$19,073,846 At each balance sheet date, outstanding forward exchange contracts not accounted for hedge accounting were as follow: Notional Amount Currency Maturity Period (In Thousands) December 31, 2019 Sell RMB/Buy US$ 2020.01-2020.02 RMB2,224,491/US$316,896 Sell HKD/Buy US$ 2020.01 HKD1,705,281/US$218,297 Sell NT$/Buy US$ 2020.01 NT$2,275,860/US$75,000 Sell US$/Buy RMB 2020.01-2020.03 US$109,000/RMB767,277 Sell US$/Buy JPY 2020.01-2020.04 US$87,398/JPY9,509,491 Sell US$/Buy MYR 2020.01-2020.05 US$26,000/MYR108,330 Sell US$/Buy NT$ 2020.01-2020.02 US$170,000/NT$5,142,441 Sell US$/Buy SGD 2020.01-2020.02 US$8,600/SGD11,691 December 31, 2020 Sell RMB/Buy US$ 2021.01 RMB756,946/US$116,093 Sell HKD/Buy US$ 2021.01 HKD4,100/US$529 Sell NT$/Buy US$ 2021.01-2021.02 NT$2,667,230/US$95,000 Sell US$/Buy RMB 2021.01-2021.04 US$363,000/RMB2,385,500 Sell US$/Buy EUR 2021.01 US$1,607/EUR1,320 Sell US$/Buy JPY 2021.01-2021.04 US$100,076/JPY10,405,845 Sell US$/Buy KRW 2021.01 US$16,000/KRW17,575,300 Sell US$/Buy MYR 2021.01-2021.04 US$24,000/MYR98,737 Sell US$/Buy NT$ 2021.01-2021.02 US$27,470/NT$776,867 Sell US$/Buy SGD 2021.01-2021.04 US$18,500/SGD24,868 As of December 31, 2020, outstanding target redemption forward contracts not accounted for hedge accounting were as follows: Notional Amount Currency Maturity Period (In Thousands) Sell EUR/Buy US$ 2022.04-2022.06 EUR23,279/US$27,475

Financial Assets at Fair Valu_2

Financial Assets at Fair Value Through Other Comprehensive Income - (FVTOCI) (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Financial Assets at Fair Value Through Other Comprehensive Income	December 31 2019 2020 NT$ NT$ US$ (Note 4) Investments in equity instruments at FVTOCI $ 755,903 $ 728,398 $ 25,940 Investments in debt instruments at FVTOCI 1,014,872 1,012,736 36,066 $ 1,770,775 $ 1,741,134 $ 62,006
Summary of Investments in Equity Instruments at Fair Value Through Other Comprehensive Income	a. Investments in equity instruments at FVTOCI December 31 2019 2020 NT$ NT$ US$ (Note 4) Unquoted ordinary shares $ 565,028 $ 567,377 $ 20,206 Unquoted preferred shares 158,718 151,329 5,389 Limited partnership 32,157 9,692 345 $ 755,903 $ 728,398 $ 25,940
Summary of Investments in Debt Instruments at Fair Value Through Other Comprehensive Income	b. Investments in debt instruments at FVTOCI December 31 2019 2020 NT$ NT$ US$ (Note 4) Unsecured subordinate corporate bonds $ 1,014,872 $ 1,012,736 $ 36,066

Trade Receivables, Net (Tables)

Trade Receivables, Net (Tables)	12 Months Ended
	Dec. 31, 2020
Statement [LineItems]
Summary of Trade Receivables, Net	December 31 2019 2020 NT$ NT$ US$ (Note 4) At amortized cost Gross carrying amount $ 77,055,280 $ 91,304,934 $ 3,251,600 Less: Allowance for impairment loss 136,497 97,358 3,467 76,918,783 91,207,576 3,248,133 At FVTOCI 2,029,690 626,413 22,308 $ 78,948,473 $ 91,833,989 $ 3,270,441
Summary of Loss Allowance of Trade Receivables Based on Group's Provision Matrix	The following table details the loss allowance of trade receivables based on the Group’s provision matrix. December 31, 2019 Not Past Due Overdue 1 to 30 days Overdue 31 to 90 Days Overdue Over 91 Days Individually Impaired Total NT$ NT$ NT$ NT$ NT$ NT$ Expected credit loss rate 0% 0%-10% 0%-70% 1%-100% 50%-100% Gross carrying amount $ 70,042,018 $ 6,111,309 $ 695,384 $ 153,458 $ 53,111 $ 77,055,280 Loss allowance (Lifetime ECLs) (12,379 ) (841 ) (26,587 ) (53,629 ) (43,061 ) (136,497 ) $ 70,029,639 $ 6,110,468 $ 668,797 $ 99,829 $ 10,050 $ 76,918,783 December 31, 2020 Not Past Due Overdue 1 to 30 days Overdue 31 to 90 Days Overdue Over 91 Days Individually Impaired Total NT$ NT$ NT$ NT$ NT$ NT$ Expected credit loss rate 0% 0%-10% 0%-70% 1%-100% 50%-100% Gross carrying amount $ 86,820,792 $ 3,823,249 $ 557,487 $ 92,873 $ 10,533 $ 91,304,934 Loss allowance (Lifetime ECLs) (18,911 ) (2,053 ) (20,629 ) (45,232 ) (10,533 ) (97,358 ) $ 86,801,881 $ 3,821,196 $ 536,858 $ 47,641 $ - $ 91,207,576 Not Past Due Overdue 1 to 30 days Overdue 31 to 90 Days Overdue Over 91 Days Individually Impaired Total US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) Expected credit loss rate 0% 0%-10% 0%-70% 1%-100% 50%-100% Gross carrying amount $ 3,091,908 $ 136,156 $ 19,854 $ 3,307 $ 375 $ 3,251,600 Loss allowance (Lifetime ECLs) (673 ) (73 ) (735 ) (1,611 ) (375 ) (3,467 ) $ 3,091,235 $ 136,083 $ 19,119 $ 1,696 $ - $ 3,248,133 The movements of the loss allowance of trade receivables for the years ended were as follows: December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Balance at January 1 $ 64,901 $ 155,389 $ 136,497 $ 4,861 Net remeasurement of loss allowance 150,128 (38,277 ) (55,742 ) (1,985 ) Reclassification - (5,877 ) (6,970 ) (248 ) Acquisition through business combinations 3,482 25,553 32,460 1,156 Amounts written off (60,109 ) - (3,944 ) (141 ) Effects of foreign currency exchange differences (3,013 ) (291 ) (4,943 ) (176 ) Balance at December 31 $ 155,389 $ 136,497 $ 97,358 $ 3,467
Summary of Loss Allowance For Current Financial Assets At Fair Value Routed Through Other Comprehensive Income	The following table details the loss allowance of trade receivables at FVTOCI based on the Group’s provision matrix. December 31, 2019 Not Past Due Overdue 1 to 30 days Overdue 31 to 90 Days Overdue Over 91 Days Individually Impaired Total NT$ NT$ NT$ NT$ NT$ NT$ Expected credit loss rate 0% - 0% 1% - Gross carrying amount $ 2,029,324 $ - $ 207 $ 160 $ - $ 2,029,691 Loss allowance (Lifetime ECLs) - - - (1 ) - (1 ) $ 2,029,324 $ - $ 207 $ 159 $ - $ 2,029,690 December 31, 2020 Not Past Due Overdue 1 to 30 days Overdue 31 to 90 Days Overdue Over 91 Days Individually Impaired Total NT$ NT$ NT$ NT$ NT$ NT$ Expected credit loss rate 0% 0% 0% - - Gross carrying amount $ 613,968 $ 9,874 $ 2,571 $ - $ - $ 626,413 Loss allowance (Lifetime ECLs) - - - - - - $ 613,968 $ 9,874 $ 2,571 $ - $ - $ 626,413 Not Past Due Overdue 1 to 30 days Overdue 31 to 90 Days Overdue Over 91 Days Individually Impaired Total US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) Expected credit loss rate 0% 0% 0% - - Gross carrying amount $ 21,864 $ 352 $ 92 $ - $ - $ 22,308 Loss allowance (Lifetime ECLs) - - - - - - $ 21,864 $ 352 $ 92 $ - $ - $ 22,308
Disclosure of transferred financial assets that are not derecognised in their entirety	The followings were the Group’s outstanding trade receivables transferred but not yet due were as follows: Counterparties Receivables Factoring Proceeds Reclassified to Other Receivables Advances Received- Unused Advances Received- Used Interest Rates on Advances Received December 31, 2019 First Commercial Bank NT$ 7,567 NT$ - NT$ - NT$ 7,567 2.2% December 31, 2020 BNP Paribas EUR 16,691 EUR 15,315 EUR 14,481 EUR 1,376 0.80% HSBC EUR 6,773 EUR 6,456 EUR 5,779 EUR 317 1.45% Citibank Taiwan Ltd. US$ 94,471 US$ - US$ - US$ 94,471 0.84%-0.95 Standard Chartered Bank US$ 53,800 US$ - US$ - US$ 53,800 0.91% First Commercial Bank NT$ 6,879 NT$ - NT$ - NT$ 6,879 1.95% Pursuant to the factoring agreements, losses from commercial disputes (such as sales returns and discounts) are borne by the Group, while losses from credit risk are borne by banks. As of December 31, 2020, the Group issued promissory notes with aggregate amounts of US$2,000 thousand to Citibank Taiwan Ltd. to compensate losses from commercial disputes. In 2020, the Group did not have material commercial dispute in the past and expected to have no material commercial dispute in the foreseeable future.

Inventories (Tables)

Inventories (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Inventories	December 31 2019 2020 NT$ NT$ US$ (Note 4) Finished goods $ 7,174,716 $ 8,788,460 $ 312,979 Work in process 2,952,182 6,816,602 242,757 Raw materials 20,996,346 29,428,008 1,048,006 Supplies 2,229,576 2,691,779 95,861 Raw materials and supplies in transit 530,930 791,610 28,191 $ 33,883,750 $ 48,516,459 $ 1,727,794

Inventories Related to Real E_2

Inventories Related to Real Estate Business (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Inventories Related to Real Estate Business	December 31 2019 2020 NT$ NT$ US$ (Note 4) Land and buildings held for sale $ 9,983 $ 625,791 $ 22,286 Construction in progress 9,619,217 11,058,328 393,815 Land held for construction 1,787,526 1,787,526 63,659 $ 11,416,726 $ 13,471,645 $ 479,760

Other Financial Assets (Tables)

Other Financial Assets (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Other Financial Assets	December 31 2019 2020 NT$ NT$ US$ (Note 4) Guarantee deposits $ 661,667 $ 516,505 $ 18,394 Pledged time deposits (Note 36) 620,817 367,550 13,089 Time deposits with original maturity of over three months 25,885 35,988 1,282 December 31 2019 2020 NT$ NT$ US$ (Note 4) Others (Note 36) $ 16,958 $ 161,957 $ 5,768 1,325,327 1,082,000 38,533 Current 765,834 551,655 19,646 Non-current $ 559,493 $ 530,345 $ 18,887

Investments Accounted for Usi_2

Investments Accounted for Using the Equity Method (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Investments Accounted for Using the Equity Method	December 31 2019 2020 NT$ NT$ US$ (Note 4) Investments in associates $ 11,805,505 $ 12,335,239 $ 439,289 Investments in joint ventures 279,702 471,434 16,789 $ 12,085,207 $ 12,806,673 $ 456,078
Summary of Investments in Associates Accounted for using the Equity Method	a. Investments in associates 1) Investments in associates accounted for using the equity method that was not individually material consisted of the following: Carrying Amount as of December 31 Operating 2019 2020 Name of Associate Main Business Location NT$ NT$ US$ (Note 4) Yann Yuan Investment Co., Ltd. (“Yann Yuan”) Engaged in investing activities R.O.C. $ 3,934,190 $ 6,670,035 $ 237,537 ChipMOS Technologies Inc. (“ChipMOS”) Engaged in the packaging and testing of semiconductors R.O.C. 4,370,075 2,406,843 85,714 M-Universe Investments Pte. Ltd. (“MU”) Investment company Singapore 1,814,699 1,848,588 65,833 Hung Ching Development & Construction Co. (“HC”) Engaged in the development, construction and leasing of real estate properties R.O.C. 1,380,162 1,352,760 48,175 Hung Ching Kwan Co. (“HCK”) Engaged in the leasing of real estate properties R.O.C. 283,105 270,087 9,618 Deca Technologies Inc. (”DECA” ） Holding company and the group engaged in manufacturing, development and marketing of wafer level packaging and interconnect technology British Cayman 323,423 87,075 3,101 12,105,654 12,635,388 449,978 Less: Deferred gain on transfer of land 300,149 300,149 10,689 $ 11,805,505 $ 12,335,239 $ 439,289 2) At each balance sheet date, the percentages of ownership held by the Group’s subsidiary were as follows: December 31 2019 2020 Yann Yuan 32.21 % 32.21 % ChipMOS 20.48 % 10.85 % MU 42.23 % 42.23 % HC 26.22 % 26.22 % HCK 27.31 % 27.31 % DECA 22.02 % 17.85 %
Summary of Fair Values of Investments in Associates with Available Published Price Quotation	5) Fair values (Level 1) of investments in associates with available published price quotation are summarized as follows: December 31 2019 2020 NT$ NT$ US$ (Note 4) ChipMOS $ 5,100,181 $ 2,710,572 $ 96,530 HC $ 1,551,033 $ 1,317,692 $ 46,926
Summary of Aggregate Information of Associates that are Not Individually Material	6) Aggregate information of associates that are not individually material For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) The Group’s share of: Net profit $ 147,535 $ 321,413 $ 545,833 $ 19,438 Other comprehensive income (loss) (613,471 ) 1,401,453 2,784,094 99,149 Total comprehensive income (loss) $ (465,936 ) $ 1,722,866 $ 3,329,927 $ 118,587
Summary of Aggregate Information of the Joint Venture that is Not Individually Material	1) Investments in joint ventures that were not individually material and accounted for using the equity method consisted of the following: Carrying Amount as of December 31 2019 2020 Operating NT$ NT$ US$ (Note 4) Name of Joint Venture Main Business Location SUMA-USI Electronics Co., Ltd. (“SUMA-USI”) Engaged in the design and production of electronic products China $ 279,702 $ 471,434 $ 16,789 2) At each balance sheet date, the percentages of ownership held by the Group’s subsidiary were as follows: December 31 2019 2020 SUMA-USI 49.00 % 49.00 % 3) In March 2019, UGKS entered into a joint venture agreement with Cancon Information Industry Co., Ltd. to establish SUMA-USI and obtained 49.00% ownership of SUMA-USI. As of December 31, 2020, the Group has invested RMB107,800 thousand (equivalent to NT$469,307 thousand (US$16,713 thousand)) in SUMA-USI. Based on the joint venture agreement, both investors jointly lead the relevant operation activities of SUMA-USI, which resulted the Group’s investment in SUMA-USI was accounted for using the equity method. 4) As disclosed in Note 29, the Group obtained control over ASEEE in April 2019. 5) Aggregate information of joint ventures that were not individually material For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) The Group’s share of: Net profit (loss) $ (306,156 ) $ (139,137 ) $ 1,780 $ 63 Other comprehensive income (loss) - (3,169 ) 3,881 138 Total comprehensive income (loss) $ (306,156 ) $ (142,306 ) $ 5,661 $ 201

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	12 Months Ended
	Dec. 31, 2020
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Summary of Property, Plant and Equipment	The carrying amounts of each class of property, plant and equipment were as follows: December 31 2019 2020 NT$ NT$ US$ (Note 4) Land $ 10,333,822 $ 10,336,568 $ 368,112 Buildings and improvements 85,409,580 82,273,186 2,929,957 December 31 2019 2020 NT$ NT$ US$ (Note 4) Machinery and equipment $ 112,996,670 $ 122,063,883 $ 4,347,004 Other equipment 6,715,694 4,680,222 166,674 Construction in progress and machinery in transit 16,637,561 13,853,465 493,357 $ 232,093,327 $ 233,207,324 $ 8,305,104 For the year ended December 31, 2018 Land Buildings and Improvements Machinery and Equipment Other Equipment Construction in Progress and Machinery in Transit Total NT$ NT$ NT$ NT$ NT$ NT$ Cost Balance at January 1, 2018 $ 3,258,518 $ 100,187,928 $ 253,198,003 $ 7,812,080 $ 5,863,713 $ 370,320,242 Additions - 144,898 192,673 84,860 38,669,807 39,092,238 Disposals - (677,206 ) (26,493,282 ) (2,251,060 ) (34,902 ) (29,456,450 ) Reclassification - 5,388,709 32,060,513 2,148,211 (39,612,324 ) (14,891 ) Acquisition through business combinations (Note 29) 6,880,400 37,127,957 95,810,062 11,122,171 5,781,189 156,721,779 Effect of foreign currency exchange differences 27,051 (464,275 ) (929,579 ) (78,095 ) 244,069 (1,200,829 ) Balance at December 31, 2018 $ 10,165,969 $ 141,708,011 $ 353,838,390 $ 18,838,167 $ 10,911,552 $ 535,462,089 Accumulated depreciation and impairment Balance at January 1, 2018 $ - $ 41,915,064 $ 187,012,805 $ 6,223,967 $ - $ 235,151,836 Depreciation expenses - 6,325,948 31,751,251 1,816,587 - 39,893,786 Impairment losses recognized - 29,531 97,680 5,860 - 133,071 Disposals - (491,033 ) (25,704,778 ) (2,070,302 ) - (28,266,113 ) Reclassification - (265 ) - - - (265 ) Acquisition through business combinations (Note 29) - 15,097,920 53,210,063 6,428,174 - 74,736,157 Effect of foreign currency exchange differences - (133,091 ) (616,601 ) (29,279 ) - (778,971 ) Balance at December 31, 2018 $ - $ 62,744,074 $ 245,750,420 $ 12,375,007 $ - $ 320,869,501 For the year ended December 31, 2019 Land Buildings and Improvements Machinery and Equipment Other Equipment Construction in Progress and Machinery in Transit Total NT$ NT$ NT$ NT$ NT$ NT$ Cost Balance at January 1, 2019 $ 10,165,969 $ 141,708,011 $ 353,838,390 $ 18,380,122 $ 10,911,552 $ 535,004,044 Additions - 806,844 413,008 76,671 61,777,364 63,073,887 Disposals - (983,690 ) (19,139,634 ) (2,507,440 ) - (22,630,764 ) Reclassification - 13,601,469 41,302,651 3,062,838 (57,221,627 ) 745,331 Acquisitions through business combinations (Note 29) 189,111 1,044,383 5,507,315 43,611 250,455 7,034,875 Effect of foreign currency exchange differences (21,258 ) (2,204,057 ) (5,176,282 ) (300,686 ) 919,817 (6,782,466 ) Balance at December 31, 2019 $ 10,333,822 $ 153,972,960 $ 376,745,448 $ 18,755,116 $ 16,637,561 $ 576,444,907 Accumulated depreciation and impairment Balance at January 1, 2019 $ - $ 62,744,074 $ 245,750,420 $ 12,194,041 $ - $ 320,688,535 Depreciation expense - 6,989,392 35,747,308 2,503,967 - 45,240,667 Impairment losses recognized - 78,562 102,056 20,388 - 201,006 Disposals - (881,149 ) (18,640,266 ) (2,503,438 ) - (22,024,853 ) Reclassification - 210,558 83,777 (103 ) - 294,232 Land Buildings and Improvements Machinery and Equipment Other Equipment Construction in Progress and Machinery in Transit Total NT$ NT$ NT$ NT$ NT$ NT$ Acquisitions through business combinations (Note 29) - 445,682 4,000,338 19,028 - 4,465,048 Effect of foreign currency exchange differences - (1,023,739 ) (3,294,855 ) (194,461 ) - (4,513,055 ) Balance at December 31, 2019 $ - $ 68,563,380 $ 263,748,778 $ 12,039,422 $ - $ 344,351,580 For the year ended December 31, 2020 Land Buildings and Improvements Machinery and Equipment Other Equipment Construction in Progress and Machinery in Transit Total NT$ NT$ NT$ NT$ NT$ NT$ Cost Balance at January 1, 2020 $ 10,333,822 $ 153,972,960 $ 376,745,448 $ 18,755,116 $ 16,637,561 $ 576,444,907 Additions - 86,409 695,561 47,137 58,195,094 59,024,201 Disposals - (365,758 ) (12,818,849 ) (2,419,423 ) (126,605 ) (15,730,635 ) Disposal of subsidiaries (Note 30) - (3,665,811 ) (3,223,448 ) (445,506 ) (792,543 ) (8,127,308 ) Reclassification - 7,367,875 52,980,977 222,066 (60,032,844 ) 538,074 Acquisitions through business combinations (Note 29) 46,388 1,142,690 3,972,397 702,500 53,828 5,917,803 Effect of foreign currency exchange differences (43,642 ) (266,536 ) (2,459,521 ) (11,008 ) (81,026 ) (2,861,733 ) Balance at December 31, 2020 $ 10,336,568 $ 158,271,829 $ 415,892,565 $ 16,850,882 $ 13,853,465 $ 615,205,309 Accumulated depreciation and impairment Balance at January 1, 2020 $ - $ 68,563,380 $ 263,748,778 $ 12,039,422 $ - $ 344,351,580 Depreciation expense - 7,401,223 36,373,712 2,241,613 - 46,016,548 Impairment losses recognized - - 981,535 10,738 - 992,273 Disposals - (300,832 ) (8,306,990 ) (2,398,756 ) - (11,006,578 ) Disposal of subsidiaries (Note 30) - (153,002 ) (345,834 ) (82,059 ) - (580,895 ) Reclassification - 3,462 497,230 (188,844 ) - 311,848 Acquisitions through business combinations (Note 29) - 548,190 3,049,895 588,935 - 4,187,020 Effect of foreign currency exchange differences - (63,778 ) (2,169,644 ) (40,389 ) - (2,273,811 ) Balance at December 31, 2020 $ - $ 75,998,643 $ 293,828,682 $ 12,170,660 $ - $ 381,997,985 Land Buildings and Improvements Machinery and Equipment Other Equipment Construction in Progress and Machinery in Transit Total US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) Cost Balance at January 1, 2020 $ 368,014 $ 5,483,368 $ 13,416,861 $ 667,917 $ 592,506 $ 20,528,666 Additions - 3,077 24,771 1,678 2,072,475 2,102,001 Disposals - (13,026 ) (456,512 ) (86,162 ) (4,509 ) (560,209 ) Disposal of subsidiaries (Note 30) - (130,549 ) (114,795 ) (15,866 ) (28,224 ) (289,434 ) Reclassification - 262,389 1,886,787 7,908 (2,137,922 ) 19,162 Acquisitions through business combinations (Note 29) 1,652 40,694 141,467 25,018 1,917 210,748 Effect of foreign currency exchange differences (1,554 ) (9,492 ) (87,590 ) (391 ) (2,886 ) (101,913 ) Balance at December 31, 2020 $ 368,112 $ 5,636,461 $ 14,810,989 $ 600,102 $ 493,357 $ 21,909,021 Accumulated depreciation and impairment Balance at January 1, 2020 $ - $ 2,441,716 $ 9,392,763 $ 428,754 $ - $ 12,263,233 Depreciation expense - 263,576 1,295,360 79,830 - 1,638,766 Impairment losses recognized - - 34,955 382 - 35,337 Disposals - (10,713 ) (295,833 ) (85,426 ) - (391,972 ) Disposal of subsidiaries (Note 30) - (5,449 ) (12,316 ) (2,922 ) - (20,687 ) Reclassification - 123 17,708 (6,725 ) - 11,106 Acquisitions through business combinations (Note 29) - 19,522 108,615 20,973 - 149,110 Effect of foreign currency exchange differences - (2,271 ) (77,267 ) (1,438 ) - (80,976 ) Balance at December 31, 2020 $ - $ 2,706,504 $ 10,463,985 $ 433,428 $ - $ 13,603,917
Summary of Property, Plant and Equipment Useful Lives	Buildings and improvements Main plant buildings 10-55 years Cleanrooms 10-20 years Others 3-20 years Machinery and equipment 2-10 years Other equipment 2-20 years

Lease Arrangements (Tables)

Lease Arrangements (Tables)	12 Months Ended
	Dec. 31, 2020
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Summary of Right-of-Use Assets	a. Right-of-use assets December 31 2019 2020 NT$ NT$ US$ (Note 4) Carrying amounts Land $ 7,036,887 $ 5,840,779 $ 208,005 Buildings and improvements 2,121,797 2,548,838 90,771 Machinery and equipment 588,443 181,065 6,448 Other equipment 45,094 49,930 1,778 $ 9,792,221 $ 8,620,612 $ 307,002 December 31 2019 2020 NT$ NT$ US$ (Note 4) Additions to right-of-use assets $ 824,268 $ 702,996 $ 25,035 Depreciation charge for right-of-use assets Land $ 215,301 $ 214,682 $ 7,645 Buildings and improvements 307,708 370,458 13,193 December 31 2019 2020 NT$ NT$ US$ (Note 4) Machinery and equipment $ 507,443 $ 335,039 $ 11,932 Other equipment 25,006 26,701 951 $ 1,055,458 $ 946,880 $ 33,721
Summary of Lease Liabilities	b. Lease liabilities December 31 2019 2020 NT$ NT$ US$ (Note 4) Carrying amounts Current $ 632,802 $ 774,444 $ 27,580 Non-current $ 5,176,123 $ 5,101,386 $ 181,673
Summary of Land and Buildings Improvements	The Group’s lease liabilities were mainly from land and buildings and improvements. The range of discount rates for lease liabilities was as follows: December 31 2019 2020 Land (%) 0.54-4.90 0.54-8.00 Buildings and improvements (%) 0.30-8.62 0.54-8.84
Summary of Other Related Lease Information	e. Other lease information December 31 2019 2020 NT$ NT$ US$ (Note 4) Expenses relating to short-term leases $ 421,924 $ 682,142 $ 24,293 Expenses relating to low-value assets leases $ 4,473 $ 5,433 $ 193 Expenses relating to variable lease payments not included in the measurement of lease liabilities $ 53,403 $ 43,112 $ 1,535 Total cash outflow for leases $ (1,511,277 ) $ (1,854,456 ) $ (66,042 )

Investment Properties (Tables)

Investment Properties (Tables)	12 Months Ended
	Dec. 31, 2020
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Summary of Investment Properties	For the year ended December 31, 2018 Land Buildings and Improvements Total NT$ NT$ NT$ Cost Balance at January 1, 2018 $ 35,965 $ 8,406,785 $ 8,442,750 Additions - 125,853 125,853 Reclassification - 14,891 14,891 Effects of foreign currency exchange differences - (137,739 ) (137,739 ) Balance at December 31, 2018 $ 35,965 $ 8,409,790 $ 8,445,755 Accumulated depreciation and impairment Balance at January 1, 2018 $ - $ 323,314 $ 323,314 Depreciation expenses - 392,667 392,667 Reclassification - 265 265 Effects of foreign currency exchange differences - (8,870 ) (8,870 ) Balance at December 31, 2018 $ - $ 707,376 $ 707,376 Carrying amount at December 31, 2018 $ 35,965 $ 7,702,414 $ 7,738,379 For the year ended December 31, 2019 Land Buildings and Improvements Right-of-use Assets Total NT$ NT$ NT$ NT$ Cost Balance at January 1, 2019 $ 35,965 $ 8,409,790 $ 6,891,947 $ 15,337,702 Additions - 2,532 - 2,532 Disposals - (1,843 ) - (1,843 ) Reclassification - (490,130 ) (21,069 ) (511,199 ) Effects of foreign currency exchange differences - (209,980 ) (303,086 ) (513,066 ) Balance at December 31, 2019 $ 35,965 $ 7,710,369 $ 6,567,792 $ 14,314,126 Accumulated depreciation and impairment Balance at January 1, 2019 $ - $ 707,376 $ 292,722 $ 1,000,098 Depreciation expenses - 377,536 216,574 594,110 Disposals - (1,240 ) - (1,240 ) Reclassification - (210,455 ) 543 (209,912 ) Effects of foreign currency exchange differences - 99,354 (22,355 ) 76,999 Balance at December 31, 2019 $ - $ 972,571 $ 487,484 $ 1,460,055 Carrying amount at December 31, 2019 $ 35,965 $ 6,737,798 $ 6,080,308 $ 12,854,071 For the year ended December 31, 2020 Land Buildings and Improvements Right-of-use Assets Total NT$ NT$ NT$ NT$ Cost Balance at January 1, 2020 $ 35,965 $ 7,710,369 $ 6,567,792 $ 14,314,126 Additions - 6,352 - 6,352 Disposals - (1,902 ) - (1,902 ) Reclassification - (3,884 ) 46,201 42,317 Effects of foreign currency exchange differences - 111,870 124,920 236,790 Balance at December 31, 2020 $ 35,965 $ 7,822,805 $ 6,738,913 $ 14,597,683 Land Buildings and Improvements Right-of-use Assets Total US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) Cost Balance at January 1, 2020 $ 1,281 $ 274,586 $ 233,896 $ 509,763 Additions - 226 - 226 Disposals - (68 ) - (68 ) Reclassification - (138 ) 1,645 1,507 Effects of foreign currency exchange differences - 3,984 4,449 8,433 Balance at December 31, 2020 $ 1,281 $ 278,590 $ 239,990 $ 519,861 Accumulated depreciation Balance at January 1, 2020 $ - $ 34,636 $ 17,360 $ 51,996 Depreciation expenses - 12,573 7,450 20,023 Disposals - (46 ) - (46 ) Reclassification - (53 ) 378 325 Effects of foreign currency exchange differences - 699 351 1,050 Balance at December 31, 2020 $ - $ 47,809 $ 25,539 $ 73,348 Carrying amount at December 31, 2020 $ 1,281 $ 230,781 $ 214,451 $ 446,513
Summary of Maturity analysis of Operating Lease Payments	The maturity analysis of lease payments receivable under operating leases of investment properties was as follows: December 31 2019 2020 NT$ NT$ US$ (Note 4) Year 1 $ 921,649 $ 880,929 $ 31,372 Year 2 744,366 688,123 24,506 Year 3 623,326 471,966 16,808 Year 4 408,634 383,307 13,651 Year 5 320,611 335,706 11,955 Year 6 onwards 830,091 664,259 23,656 $ 3,848,677 $ 3,424,290 $ 121,948
Summary of Investment Properties, Useful Lives	The investment properties were depreciated on a straight-line basis over the following useful lives: Main buildings 10-40 years Right-of-use assets 15-50 years
Summary of Investment Properties, Fair Value	The fair value of the investment properties was as follows: December 31 2019 2020 NT$ NT$ US$ (Note 4) Fair value $ 19,586,287 $ 19,799,714 $ 705,118

Goodwill (Tables)

Goodwill (Tables)	12 Months Ended
	Dec. 31, 2020
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Summary of Goodwill	Cost Accumulated impairment Carrying amount NT$ NT$ NT$ For the year ended December 31, 2018 Balance at January 1, 2018 $ 12,348,607 $ 2,414,113 $ 9,934,494 Cost Accumulated impairment Carrying amount NT$ NT$ NT$ Acquisition through business combinations (Note 29) 39,990,231 - 39,990,231 Effect of foreign currency exchange differences 49,721 - 49,721 Balance at December 31, 2018 $ 52,388,559 $ 2,414,113 $ 49,974,446 For the year ended December 31, 2019 Balance at January 1, 2019 $ 52,388,559 $ 2,414,113 $ 49,974,446 Acquisition through business combinations (Note 29) 264,977 - 264,977 Effect of foreign currency exchange differences (40,987 ) - (40,987 ) Balance at December 31, 2019 $ 52,612,549 $ 2,414,113 $ 50,198,436 For the year ended December 31, 2020 Balance at January 1, 2020 $ 52,612,549 $ 2,414,113 $ 50,198,436 Acquisition through business combinations (Note 29) 4,625,269 - 4,625,269 Effect of foreign currency exchange differences (46,266 ) - (46,266 ) Balance at December 31, 2020 $ 57,191,552 $ 2,414,113 $ 54,777,439 Cost Accumulated Impairment Carrying Amount US$ (Note 4) US$ (Note 4) US$ (Note 4) For the year ended December 31, 2020 Balance at January 1, 2020 $ 1,873,666 $ 85,973 $ 1,787,693 Acquisition through business combinations (Note 29) 164,718 - 164,718 Effect of foreign currency exchange differences (1,647 ) - (1,647 ) Balance at December 31, 2020 $ 2,036,737 $ 85,973 $ 1,950,764 Cost Accumulated impairment Carrying amount NT$ NT$ NT$ Acquisition through business combinations (Note 29) 39,990,231 - 39,990,231 Effect of foreign currency exchange differences 49,721 - 49,721 Balance at December 31, 2018 $ 52,388,559 $ 2,414,113 $ 49,974,446 For the year ended December 31, 2019 Balance at January 1, 2019 $ 52,388,559 $ 2,414,113 $ 49,974,446 Acquisition through business combinations (Note 29) 264,977 - 264,977 Effect of foreign currency exchange differences (40,987 ) - (40,987 ) Balance at December 31, 2019 $ 52,612,549 $ 2,414,113 $ 50,198,436 For the year ended December 31, 2020 Balance at January 1, 2020 $ 52,612,549 $ 2,414,113 $ 50,198,436 Acquisition through business combinations (Note 29) 4,625,269 - 4,625,269 Effect of foreign currency exchange differences (46,266 ) - (46,266 ) Balance at December 31, 2020 $ 57,191,552 $ 2,414,113 $ 54,777,439 Cost Accumulated Impairment Carrying Amount US$ (Note 4) US$ (Note 4) US$ (Note 4) For the year ended December 31, 2020 Balance at January 1, 2020 $ 1,873,666 $ 85,973 $ 1,787,693 Acquisition through business combinations (Note 29) 164,718 - 164,718 Effect of foreign currency exchange differences (1,647 ) - (1,647 ) Balance at December 31, 2020 $ 2,036,737 $ 85,973 $ 1,950,764
Summary of Carrying Amounts of Goodwill Allocated to Cash-generating Units	The carrying amounts of goodwill allocated to cash-generating units were as follows: December 31 2019 2020 Cash-generating units NT$ NT$ US$ (Note 4) Packaging segment $ 35,717,828 $ 35,703,625 $ 1,271,496 Testing segment 13,421,321 13,365,068 475,964 EMS segment (Note 29) 903,346 5,560,645 198,029 Others 155,941 148,101 5,275 $ 50,198,436 $ 54,777,439 $ 1,950,764 b. Impairment assessment At the end of each year, the Group performs evaluation of goodwill for impairment by reviewing the recoverable amounts based on value in use which incorporates cash flow projections estimated by management covering a five-year period. The cash flows beyond that five-year period are extrapolated using a steady per annum growth rate. In assessing value in use, the estimated future cash flows are discounted to their present value using annual pre-tax discount rates which were 9.74%-10.22%, 9.59%-14.99% and 10.39%-14.71% as of December 31, 2018, 2019 and 2020, respectively. For the years ended December 31, 2018, 2019 and 2020, no impairment loss was recognized. The key assumption used in calculating each segment’s value in use also included the growth rates for operating revenues, which were based on the forecast for the Group and the industry as well as the Group’s historical performance. Management believes that any reasonably possible change in the key assumptions on which the recoverable amount was based would not cause the carrying amount of the cash-generating unit to exceed its recoverable amount.

Other Intangible Assets (Tables

Other Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2020
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Summary of Carrying Amounts of Each Class of Other Intangible Assets	The carrying amounts of each class of other intangible assets were as follows: December 31 2019 2020 NT$ NT$ US$ (Note 4) Customer relationships $ 9,333,333 $ 8,334,203 $ 296,802 Computer software 1,929,539 2,678,867 95,401 Patents and acquired specific technology 17,718,523 15,720,213 559,837 Others 42,997 75,385 2,685 $ 29,024,392 $ 26,808,668 $ 954,725 For the year ended December 31, 2018 Customer Relationships Computer Software Patents and Acquired Specific Technology Others Total NT$ NT$ NT$ NT$ NT$ Cost Balance at January 1, 2018 $ 915,636 $ 3,686,452 $ 389,486 $ 198,754 $ 5,190,328 Additions - 528,883 - 8,776 537,659 Disposals - (95,358 ) (231 ) (4,000 ) (99,589 ) Acquisition through business combinations (Note 29) 11,000,000 274,868 20,200,000 32,800 31,507,668 Effect of foreign currency exchange differences - 6,200 (899 ) (332 ) 4,969 Balance at December 31, 2018 $ 11,915,636 $ 4,401,045 $ 20,588,356 $ 235,998 $ 37,141,035 Accumulated amortization Balance at January 1, 2018 $ 801,860 $ 2,822,121 $ 70,084 $ 89,398 $ 3,783,463 Amortization expense 746,979 373,536 1,263,309 18,626 2,402,450 Disposals - (95,202 ) (231 ) (4,000 ) (99,433 ) Acquisition through business combinations (Note 29) - 137,799 - 15,483 153,282 Effect of foreign currency exchange differences - 3,109 (475 ) 939 3,573 Balance at December 31, 2018 $ 1,548,839 $ 3,241,363 $ 1,332,687 $ 120,446 $ 6,243,335 For the year ended December 31, 2019 Customer Relationships Computer Software Patents and Acquired Specific Technology Others Total NT$ NT$ NT$ NT$ NT$ Cost Balance at January 1, 2019 $ 11,915,636 $ 4,401,045 $ 20,588,356 $ 83,657 $ 36,988,694 Additions - 1,358,533 - (7,625 ) 1,350,908 Disposals or derecognization (915,635 ) (1,123,446 ) - (6,315 ) (2,045,396 ) Acquisition through business combinations (Note 29) - 19,944 732,604 - 752,548 Customer Relationships Computer Software Patents and Acquired Specific Technology Others Total NT$ NT$ NT$ NT$ NT$ Effect of foreign currency exchange differences $ - $ (49,198 ) $ (2,264 ) $ (1,417 ) $ (52,879 ) Balance at December 31, 2019 $ 11,000,001 $ 4,606,878 $ 21,318,696 $ 68,300 $ 36,993,875 Accumulated amortization Balance at January 1, 2019 $ 1,548,839 $ 3,241,363 $ 1,332,687 $ 27,772 $ 6,150,661 Amortization expense 1,033,464 583,300 1,955,703 4,139 3,576,606 Disposals or derecognization (915,635 ) (1,116,512 ) - (6,315 ) (2,038,462 ) Acquisition through business combinations (Note 29) - 7,765 313,422 - 321,187 Effect of foreign currency exchange differences - (38,577 ) (1,639 ) (293 ) (40,509 ) Balance at December 31, 2019 $ 1,666,668 $ 2,677,339 $ 3,600,173 $ 25,303 $ 7,969,483 Customer Relationships Computer Software Patents and Acquired Specific Technology Others Total NT$ NT$ NT$ NT$ NT$ Effect of foreign currency exchange differences $ - $ (49,198 ) $ (2,264 ) $ (1,417 ) $ (52,879 ) Balance at December 31, 2019 $ 11,000,001 $ 4,606,878 $ 21,318,696 $ 68,300 $ 36,993,875 Accumulated amortization Balance at January 1, 2019 $ 1,548,839 $ 3,241,363 $ 1,332,687 $ 27,772 $ 6,150,661 Amortization expense 1,033,464 583,300 1,955,703 4,139 3,576,606 Disposals or derecognization (915,635 ) (1,116,512 ) - (6,315 ) (2,038,462 ) Acquisition through business combinations (Note 29) - 7,765 313,422 - 321,187 Effect of foreign currency exchange differences - (38,577 ) (1,639 ) (293 ) (40,509 ) Balance at December 31, 2019 $ 1,666,668 $ 2,677,339 $ 3,600,173 $ 25,303 $ 7,969,483 For the year ended December 31, 2020 Customer Relationships Computer Software Patents and Acquired Specific Technology Others Total NT$ NT$ NT$ NT$ NT$ Cost Balance at January 1, 2020 $ 11,000,001 $ 4,606,878 $ 21,318,696 $ 68,300 $ 36,993,875 Additions - 951,439 171 31,045 982,655 Disposals or derecognization - (55,413 ) - (14,594 ) (70,007 ) Disposal of subsidiaries (Note 30) - (38,125 ) - - (38,125 ) Acquisition through business combinations (Note 29) 103,633 1,451,123 - 114,269 1,669,025 Effect of foreign currency exchange differences 552 (66,459 ) 312 (19,160 ) (84,755 ) Balance at December 31, 2020 $ 11,104,186 $ 6,849,443 $ 21,319,179 $ 179,860 $ 39,452,668 Customer Relationships Computer Software Patents and Acquired Specific Technology Others Total NT$ NT$ NT$ NT$ NT$ Accumulated amortization Balance at January 1, 2020 $ 1,666,668 $ 2,677,339 $ 3,600,173 $ 25,303 $ 7,969,483 Amortization expense 1,000,000 729,330 1,998,554 5,493 3,733,377 Disposals or derecognization - (47,345 ) - (5,044 ) (52,389 ) Disposal of subsidiaries (Note 30) - (10,688 ) - - (10,688 ) Acquisition through business combinations (Note 29) 102,768 843,746 - 79,673 1,026,187 Effect of foreign currency exchange differences 547 (21,806 ) 239 (950 ) (21,970 ) Balance at December 31, 2020 $ 2,769,983 $ 4,170,576 $ 5,598,966 $ 104,475 $ 12,644,000 Customer Relationships Computer Software Patents and Acquired Specific Technology Others Total US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) Cost Balance at January 1, 2020 $ 391,738 $ 164,063 $ 759,213 $ 2,432 $ 1,317,446 Additions - 33,883 6 1,106 34,995 Disposals or derecognization - (1,973 ) - (520 ) (2,493 ) Disposal of subsidiaries (Note 30) - (1,358 ) - - (1,358 ) Acquisition through business combinations (Note 29) 3,691 51,678 - 4,069 59,438 Effect of foreign currency exchange differences 20 (2,367 ) 11 (682 ) (3,018 ) Balance at December 31, 2020 $ 395,449 $ 243,926 $ 759,230 $ 6,405 $ 1,405,010 Customer Relationships Computer Software Patents and Acquired Specific Technology Others Total US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) Accumulated amortization Balance at January 1, 2020 $ 59,354 $ 95,347 $ 128,211 $ 901 $ 283,813 Amortization expense 35,613 25,973 71,173 196 132,955 Disposals or derecognization - (1,686 ) - (180 ) (1,866 ) Disposal of subsidiaries (Note 30) - (381 ) - - (381 ) Acquisition through business combinations (Note 29) 3,660 30,048 - 2,837 36,545 Effect of foreign currency exchange differences 19 (776 ) 9 (33 ) (781 ) Balance at December 31, 2020 $ 98,646 $ 148,525 $ 199,393 $ 3,721 $ 450,285
Summary of Other Intangible Assets Useful Lives	Each class of other intangible assets was amortized on the straight-line basis over the following useful lives: Customer relationships 11 years Computer software 2-10 years Patents and acquired specific technology 5-17 years Others 5-32 years

Borrowings (Tables)

Borrowings (Tables)	12 Months Ended
	Dec. 31, 2020
Statement [LineItems]
Summary of Long-term Notes Payable	3) Long-term notes payable - only as of December 31, 2019 December 31, 2019 NT$ Commercial papers $ 100,016 Less: unamortized discounts 2,137 97,879 Less: current portion 94,798 $ 3,081 Annual interest rate (%) 5.02-6.89
Short Term Bank Loans [member]
Statement [LineItems]
Summary of Borrowings	a. Short-term borrowings Bank loans mainly represented unsecured revolving loans and letters of credit. December 31 2019 2020 NT$ NT$ US$ (Note 4) Secured bank loans, annual interest rate was 0.90%-1.87% as of December 31, 2020 $ - $ 300,495 $ 10,701 Unsecured bank loans, annual interest rates were 0.70%-5.40% and 0.58%-3.83% as of December 31, 2019 and 2020, respectively 40,572,329 34,297,362 1,221,416 40,572,329 34,597,857 1,232,117 Less: financial liabilities for hedging - current (Note 34) 3,233,301 3,307,018 117,771 $ 37,339,028 $ 31,290,839 $ 1,114,346
Long Term Bank Loans [member]
Statement [LineItems]
Summary of Borrowings	b. Long-term borrowings 1) Bank loans December 31 2019 2020 NT$ NT$ US$ (Note 4) Revolving bank loans Syndicated bank loans - repayable through April 2021 to October 2022, annual interest rates were 1.80% and 1.15%-1.17% as of December 31, 2019 and 2020 (Note 36) $ 20,000,000 $ 12,536,424 $ 446,454 Others - repayable through January 2021 to July 2029, annual interest rates were 0.82%-4.13% and 0.56%-4.15% as of December 31, 2019 and 2020, respectively 105,214,824 84,146,125 2,996,657 Mortgage loans Repayable through January 2021 to December 2033, annual interest rates were 2.43%-4.90% and 1.90%-4.90% as of December 31, 2019 and 2020, respectively 4,880,822 10,813,997 385,114 130,095,646 107,496,546 3,828,225 Less: unamortized discounts 10,292 104,323 3,715 130,085,354 107,392,223 3,824,510 Less: current portion 5,017,970 2,250,121 80,133 financial liabilities for hedging - current (Note 34) - 1,970,307 70,168 financial liabilities for hedging - non-current (Note 34) - 5,910,919 210,503 $ 125,067,384 $ 97,260,876 $ 3,463,706
Longterm Bills Payable [member]
Statement [LineItems]
Summary of Borrowings	2) Long-term bills payable December 31 2019 2020 NT$ NT$ US$ (Note 4) Ta Ching Bills Finance Corporation, repayable in March 2022, annual interest rates were 1.01%-1.03% and 0.91% as of December 31, 2019 and 2020, respectively $ 3,100,000 $ 1,000,000 $ 35,613 December 31 2019 2020 NT$ NT$ US$ (Note 4) Mega Bills Finance Corporation, repayable in March 2022, annual interest rates were 1.04% and 0.92%-0.93% as of December 31, 2019 and 2020, respectively $ 2,000,000 $ 2,000,000 $ 71,225 China Bills Finance Corporation, repayable through March 2022 to December 2022, annual interest rates were 1.02%-1.05% and 0.65%-0.90% as of December 31, 2019 and 2020, respectively 2,800,000 2,000,000 71,225 International Bills Finance Corporation, early repaid through March 2020 to June 2020, annual interest rates were 1.02%-1.05% as of December 31, 2019 3,000,000 - - 10,900,000 5,000,000 178,063 Less: unamortized discounts 4,635 1,498 53 $ 10,895,365 $ 4,998,502 $ 178,010

Bonds Payable (Tables)

Bonds Payable (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Bonds Payable	December 31 2019 2020 NT$ NT$ US$ (Note 4) Unsecured domestic bonds Repayable at maturity in January 2021 and interest due annually with annual interest rate at 1.30% $ 7,000,000 $ 7,000,000 $ 249,288 December 31 2019 2020 NT$ NT$ US$ (Note 4) Repayable at maturity in January 2023 and interest due annually with annual interest rate at 1.50% $ 2,000,000 $ 2,000,000 $ 71,225 Repayable at maturity in January 2022 and interest due annually with annual interest rate at 1.25% 3,700,000 3,700,000 131,766 Repayable at maturity in January 2024 and interest due annually with annual interest rate at 1.45% 4,300,000 4,300,000 153,134 Repayable at maturity in April 2024 and interest due annually with annual interest rate at 0.90% 6,500,000 6,500,000 231,481 Repayable at maturity in April 2026 and interest due annually with annual interest rate at 1.03% 3,500,000 3,500,000 124,644 Repayable at maturity in April 2025 and interest due annually with annual interest rate at 0.90% - 10,000,000 356,125 Repayable at maturity in August 2023 and interest due annually with annual interest rate at 0.72% - 3,000,000 106,838 Repayable at maturity in August 2025 and interest due annually with annual interest rate at 0.85% - 5,000,000 178,063 Repayable at maturity in August 2027 and interest due annually with annual interest rate at 0.95% - 2,000,000 71,225 Unsecured international bonds US$200,000 thousand (linked to New Taiwan dollar), repayable at maturity in October 2022 and interest due quarterly with annual interest rate at 2.15% 6,204,800 6,204,800 220,969 US$100,000 thousand (linked to New Taiwan dollar), repayable at maturity in October 2024 and interest due quarterly with annual interest rate at 2.50% 3,102,400 3,102,400 110,484 Secured domestic bonds Repayable at maturity in December 2020 and interest due annually with nil annual interest rate 250,000 - - 36,557,200 56,307,200 2,005,242 Less: discounts on bonds payable 35,045 53,646 1,910 36,522,155 56,253,554 2,003,332 Less: current portion of bonds payable 250,000 6,999,951 249,286 $ 36,272,155 $ 49,253,603 $ 1,754,046

Other Payables (Tables)

Other Payables (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Other Payables	December 31 2019 2020 NT$ NT$ US$ (Note 4) Accrued salary and bonus $ 10,384,089 $ 12,448,548 $ 443,324 Payables for property, plant and equipment 14,282,564 10,013,971 356,623 Accrued employees’ compensation and remuneration to directors 3,206,036 4,405,981 156,908 Accrued employee insurance 900,367 1,105,122 39,356 Accrued utilities 504,866 536,491 19,106 Others 9,903,768 10,905,510 388,373 $ 39,181,690 $ 39,415,623 $ 1,403,690

Retirement Benefit Plans (Table

Retirement Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Defined Benefit Plans Amounts Included in Consolidated Balance Sheets	4) The amounts included in the consolidated balance sheets arising from the Group’s obligation in respect of its defined benefit plans excluding those for executive managers were as follows: December 31 2019 2020 NT$ NT$ US$ (Note 4) Present value of the defined benefit obligation $ 10,668,574 $ 12,159,145 $ 433,018 Fair value of the plan assets (5,742,178 ) (5,962,305 ) (212,333 ) Present value of unfunded defined benefit obligation 4,926,396 6,196,840 220,685 Recorded under other payables (19,014 ) (102,367 ) (3,646 ) Recorded under other non-current assets 11,910 26,306 937 Net defined benefit liability $ 4,919,292 $ 6,120,779 $ 217,976
Summary of Movements in Net Defined Benefit Liability (Asset)	Movements in net defined benefit liability (asset) were as follows: Present Value of the Defined Benefit Obligation Fair Value of the Plan Assets Net Defined Benefit Liability (Asset) NT$ NT$ NT$ Balance at January 1, 2018 $ 7,910,638 $ (4,341,373 ) $ 3,569,265 Service cost Current service cost 224,126 - 224,126 Net interest expense (income) 178,779 (122,709 ) 56,070 Recognized in profit or loss 402,905 (122,709 ) 280,196 Remeasurement Return on plan assets (excluding amounts included in net interest) - (16,589 ) (16,589 ) Actuarial (gain) loss Changes in financial assumptions (8,643 ) - (8,643 ) Experience adjustments 302,499 - 302,499 Changes in demographic assumptions 8,190 - 8,190 Changes in other assumptions 22,723 - 22,723 Recognized in other comprehensive income 324,769 (16,589 ) 308,180 Contributions from the employer - (364,237 ) (364,237 ) Benefits paid from the pension fund (541,989 ) 541,989 - the Group (295,953 ) - (295,953 ) Business combinations 2,522,805 (1,210,524 ) 1,312,281 Exchange differences on foreign plans (26,036 ) 21,320 (4,716 ) Balance at December 31, 2018 10,297,139 (5,492,123 ) 4,805,016 Service cost Current service cost 211,226 - 211,226 Net interest expense (income) 151,635 (97,387 ) 54,248 Recognized in profit or loss 362,861 (97,387 ) 265,474 Remeasurement Return on plan assets (excluding amounts included in net interest) - (104,516 ) (104,516 ) Actuarial (gain) loss Changes in financial assumptions 398,732 - 398,732 Experience adjustments 70,374 - 70,374 Changes in demographic assumptions (2,329 ) - (2,329 ) Recognized in other comprehensive income 466,777 (104,516 ) 362,261 (Continued) Present Value of the Defined Benefit Obligation Fair Value of the Plan Assets Net Defined Benefit Liability (Asset) NT$ NT$ NT$ Contributions from the employer $ - $ (514,617 ) $ (514,617 ) Benefits paid from the pension fund (393,897 ) 393,897 - the Group (21,439 ) - (21,439 ) Business combinations 62,857 (28,380 ) 34,477 Exchange differences on foreign plans (105,724 ) 100,948 (4,776 ) Balance at December 31, 2019 $ 10,668,574 $ (5,742,178 ) $ 4,926,396 Service cost Current service cost 193,693 - 193,693 Past service cost and gain on settlements (25,891 ) - (25,891 ) Net interest expense (income) 119,314 (81,114 ) 38,200 Recognized in profit or loss 287,116 (81,114 ) 206,002 Remeasurement Return on plan assets (excluding amounts included in net interest) - (109,616 ) (109,616 ) Actuarial (gain) loss Changes in financial assumptions 465,433 - 465,433 Experience adjustments 281,661 - 281,661 Changes in demographic assumptions (36,627 ) - (36,627 ) Recognized in other comprehensive income 710,467 (109,616 ) 600,851 Contributions from the employer - (620,433 ) (620,433 ) Benefits paid from the pension fund (552,430 ) 603,137 50,707 the Group (14,520 ) - (14,520 ) Assets extinguished on settlement - 11,910 11,910 Business combinations 1,018,480 - 1,018,480 Exchange differences on foreign plans 41,458 (24,011 ) 17,447 Balance at December 31, 2020 $ 12,159,145 $ (5,962,305 ) $ 6,196,840 Present Value of the Defined Benefit Obligation Fair Value of the Plan Assets Net Defined Benefit Liability (Asset) US$ (Note 4) US$ (Note 4) US$ (Note 4) Balance at January 1, 2020 $ 379,935 $ (204,493 ) $ 175,442 Service cost Current service cost 6,898 - 6,898 Present Value of the Defined Benefit Obligation Fair Value of the Plan Assets Net Defined Benefit Liability (Asset) US$ (Note 4) US$ (Note 4) US$ (Note 4) Past service cost and gain on settlements $ (922 ) $ - $ (922 ) Net interest expense (income) 4,249 (2,889 ) 1,360 Recognized in profit or loss 10,225 (2,889 ) 7,336 Remeasurement Return on plan assets (excluding amounts included in net interest) - (3,904 ) (3,904 ) Actuarial (gain) loss Changes in financial assumptions 16,575 - 16,575 Experience adjustments 10,031 - 10,031 Changes in demographic assumptions (1,304 ) - (1,304 ) Recognized in other comprehensive income 25,302 (3,904 ) 21,398 Contributions from the employer - (22,095 ) (22,095 ) Benefits paid from the pension fund (19,673 ) 21,479 1,806 the Group (517 ) - (517 ) Assets extinguished on settlement - 424 424 Business combinations 36,270 - 36,270 Exchange differences on foreign plans 1,476 (855 ) 621 Balance at December 31, 2020 $ 433,018 $ (212,333 ) $ 220,685
Summary of Fair Value of the Plan Assets by Major Categories	5) The fair value of the plan assets by major categories at each balance sheet date was as follows: December 31 2019 2020 NT$ NT$ US$ (Note 4) Cash $ 2,396,657 $ 2,236,340 $ 79,642 Equity instruments 2,315,637 2,459,708 87,596 Debt instruments 1,029,884 1,092,115 38,893 Others - 174,142 6,202 Total $ 5,742,178 $ 5,962,305 $ 212,333
Summary of Key Assumptions Used for the Actuarial Valuations	8) The present value of the defined benefit obligation and the related current service cost and past service cost were measured using the Projected Unit Credit Method. Except the pension plans for executive managers, the key assumptions used for the actuarial valuations were as follow: December 31 2019 2020 Discount rates (%) 0.08-2.85 0.00-2.77 Expected rates of salary increase (%) 1.00-4.01 1.00-4.06
Summary of Sensitivity Analysis on Defined Obligations	The sensitivity analysis below has been determined based on reasonably possible changes of the respective assumptions occurring at each balance sheet date, while holding all other assumptions constant. December 31 2019 2020 NT$ NT$ US$ (Note 4) Discount Rate 0.5% higher $ (555,266 ) $ (617,803 ) $ (22,002 ) 0.5% lower $ 601,616 $ 600,451 $ 21,384 Expected rates of salary increase 0.5% higher $ 591,915 $ 611,217 $ 21,767 0.5% lower $ (545,528 ) $ (565,555 ) $ (20,141 )
Summary of Maturity Analysis of Undiscounted Pension Benefit	9) Maturit y December 31 2019 2020 NT$ NT$ US$ (Note 4) No later than 1 year $ 422,067 $ 498,092 $ 17,738 Later than 1 year but not later than 5 years 2,081,540 2,553,522 90,937 Later than 5 years 12,216,422 12,325,576 438,945 $ 14,720,029 $ 15,377,190 $ 547,620

Equity (Tables)

Equity (Tables)	12 Months Ended
	Dec. 31, 2020
Statement [LineItems]
Summary of Share Capital	a. Share capita l Ordinary shares December 31 2019 2020 Numbers of shares authorized (in thousands) 5,000,000 5,500,000 Numbers of shares reserved (in thousands) Employee share options 400,000 400,000 Number of shares issued and fully paid (in thousands) 4,330,528 4,351,592 December 31 2019 2020 NT$ NT$ US$ (Note 4) Share capital authorized $ 50,000,000 $ 55,000,000 $ 1,958,689 Share capital reserved Employee share options $ 4,000,000 $ 4,000,000 $ 142,450 Share capital issued and fully paid $ 43,305,287 $ 43,515,920 $ 1,549,712
Summary of Capital Surplus	b. Capital surplus December 31 2019 2020 NT$ NT$ US$ (Note 4) May be used to offset a deficit, distributed as cash dividends, or transferred to share capital (1) Issuance of ordinary shares $ 13,070,330 $ 13,548,426 $ 482,494 Merger by share exchange 117,693,658 117,693,658 4,191,369 (Continued) December 31 2019 2020 NT$ NT$ US$ (Note 4) Difference between consideration and the carrying amount of the subsidiaries’ net assets during actual disposal or acquisition $ 3,254,489 $ 3,240,987 $ 115,420 134,018,477 134,483,071 4,789,283 May be used to offset a deficit only Changes in percentage of ownership interest in subsidiaries (2) 891,876 1,451 52 Treasury share transactions 364,708 510,449 18,178 Exercised employee share options 1,443,995 1,617,254 57,595 Expired share options (Note 28) 645,903 645,903 23,002 Share of changes in capital surplus of associates 16,266 41,239 1,469 Dividends that the claim period has elapsed and unclaimed by shareholders 1,942 3,550 126 3,364,690 2,819,846 100,422 May not be used for any purpose Employee share options 1,304,250 1,894,952 67,484 Others (3) 222,946 569,681 20,288 1,527,196 2,464,633 87,772 $ 138,910,363 $ 139,767,550 $ 4,977,477 (Concluded) 1) Such capital surplus may be used to offset a deficit; in addition, when the Company has no deficit, such capital surplus may be distributed as cash dividends or transferred to share capital (limited to a certain percentage of the Company’s capital surplus and once a year). 2) Such capital surplus arises from the effects of changes in ownership interests in subsidiaries resulting from equity transactions other than actual disposals or acquisitions, or from changes in capital surplus of subsidiaries accounted for using the equity method. 3) Such capital surplus represents the excess of the carrying amount of related accounts over the par value due to employee share options exercised and the Company has not completed registration formalities.
Disclosure of Detailed Information About Appropriation of Retained Earnings Explanatory	The appropriation of earnings for 2018 and 2019 resolved at the Company’s annual shareholders’ meetings in June 2019 and June 2020, respectively were as follows: Appropriation of Earnings Dividends Per Share For Year 2018 For Year 2019 For Year 2018 For Year 2019 NT$ NT$ NT$ NT$ (in dollars) (in dollars) Legal reserve $ 2,203,895 $ 1,697,489 Special reserve 3,548,844 3,944,915 Cash dividends 10,806,454 8,668,331 $ 2.5 $ 2.0 $ 16,559,193 $ 14,310,735
Summary of Unrealized Gain (Loss) on Financial Assets at FVTOCI	2) Unrealized gain (loss) on financial assets at FVTOCI For the Year Ended December 31 2019 2020 NT$ NT$ US$ (Note 4) Balance at January 1 $ (1,015,107 ) $ (203,098 ) $ (7,233 ) Unrealized gain (loss) recognized during the year Debt instruments (2,052 ) (2,136 ) (76 ) Equity instruments (283,472 ) (405,020 ) (14,424 ) Share from associates and joint venture accounted for using the equity method 1,501,689 2,655,570 94,572 Realized gain (loss) recognized during the year Share from the disposal of associates and joint venture accounted for using the equity method - 1,094 39 Equity instruments - 16,383 583 Share from associates and joint venture accounted for using the equity method (404,156 ) (34,891 ) (1,242 ) Balance at December 31 $ (203,098 ) $ 2,027,902 $ 72,219
Schedule of detailed information about hedges of net investments of foreign operations	3) Gain (loss) on hedging instruments - hedges of net investments of foreign operations For the year ended December 31, 2020 NT$ US$ (Note 4) Balance at January 1 $ - $ - Recognized during the period Foreign currency risk – loans denominated in foreign currency (429,265 ) (15,287 ) Balance at December 31 $ (429,265 ) $ (15,287 )
Summary of Shares Held By Subsidiaries	The Company’s shares held by its subsidiaries at each balance sheet date were as follows: Shares Held by Subsidiaries Carrying Amount Carrying Amount Fair Value Fair Value (in thousand shares) NT$ US$ (Note 4) NT$ US$ (Note 4) December 31, 2019 ASE Test 44,100 $ 1,380,721 $ 3,669,140 J&R Holding 23,352 381,709 1,942,876 ASE Test, Inc. 5,489 196,677 456,717 72,941 $ 1,959,107 $ 6,068,733 December 31, 2020 ASE Test 44,100 $ 1,380,721 $ 49,171 $ 3,585,349 $ 127,683 J&R Holding 23,352 381,709 13,594 1,898,508 67,611 ASE Test, Inc. 5,489 196,677 7,004 446,287 15,893 72,941 $ 1,959,107 $ 69,769 $ 5,930,144 $ 211,187
Summary of Non-controlling Interests	f. Non-controlling interests For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Balance at January 1 $ 13,195,312 $ 17,639,487 $ 13,374,912 $ 476,315 Share of profit for the year 1,203,588 1,207,974 1,681,320 59,876 Other comprehensive income (loss) Exchange difference on translating foreign operations (198,365 ) (414,010 ) 178,480 6,356 Unrealized (loss) gain on equity instruments at FVTOCI (23,928 ) (10,773 ) 1,321 47 Loss from hedging - - (145,559 ) (5,184 ) Remeasurement on defined benefit plans (30,079 ) (7,422 ) (9,075 ) (323 ) Non-controlling interests arising from acquisition or disposal of subsidiaries (Note 29) 3,582,866 666,651 (5,658 ) (202 ) Subscribing for ordinary shares from subsidiaries’ cash capital increase - 83,044 - - Acquisition of non-controlling interests in subsidiaries (Note 31) (2,492,915 ) (5,084,785 ) (116,738 ) (4,157 ) Issuance of new ordinary shares by subsidiaries (Note 29) - - 1,711,453 60,949 Partial disposal of subsidiaries 1,693,064 - - - Subsidiaries’ buy back of their own outstanding ordinary shares (Note 31) (801,884 ) (2,017,319 ) (2,299,533 ) (81,892 ) Non-controlling interest relating to outstanding vested employee share options granted by subsidiaries 1,936,643 1,672,310 1,591,904 56,692 Cash dividends to non-controlling interests (424,815 ) (360,245 ) (346,774 ) (12,350 ) Balance at December 31 $ 17,639,487 $ 13,374,912 $ 15,616,053 $ 556,127
Exchange differences on translating foreign operations [member]
Statement [LineItems]
Summary of Other Reserves	1) Exchange differences on translating foreign operations For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Balance at January 1 $ (6,733,659 ) $ (5,888,574 ) $ (10,762,684 ) $ (383,286 ) Recognized for the year Exchange differences on translating foreign operations 426,186 (4,788,135 ) (1,173,204 ) (41,781 ) (Continued) For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Share from associates and joint venture accounted for using the equity method $ 136,608 $ (85,975 ) $ 101,038 $ 3,598 Reclassification adjustments Disposal of associates and joint venture accounted for using the equity method 282,291 - 29,971 1,067 Disposal of foreign operations - - 162,940 5,803 Balance at December 31 $ (5,888,574 ) $ (10,762,684 ) $ (11,641,939 ) $ (414,599 ) (Concluded)

Profit Before Income Tax (Table

Profit Before Income Tax (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Other Operating Income and Expenses, Net	a. Other operating income and expenses, net For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Rental income $ 182,411 $ 136,301 $ 153,682 $ 5,473 Gains (losses) on disposal of property, plant and equipment and other assets (14,644 ) (164,187 ) 732,796 26,097 Impairment losses on property, plant and equipment (Note 15) (133,071 ) (201,006 ) (992,273 ) (35,337 ) Loss on damages and claims (24,114 ) (459,544 ) (176,888 ) (6,299 ) Others 361,001 419,881 785,175 27,961 $ 371,583 $ (268,555 ) $ 502,492 $ 17,895
Summary of Other Income	b. Other income For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Government subsidy $ 435,950 $ 624,351 $ 803,049 $ 28,599 Interest income 466,211 549,681 520,783 18,546 Dividends income 190,397 185,061 150,715 5,367 $ 1,092,558 $ 1,359,093 $ 1,474,547 $ 52,512
Summary of Other Gains, net	c. Other gains, net For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Remeasurement gain on investments accounted for using the equity method due to step acquisition (Note 29) $ 7,421,408 $ 319,712 $ - $ - Net gains on financial assets mandatorily at FVTPL 3,388,485 3,631,763 3,211,125 114,356 Net losses arising on financial instruments held for trading (1,398,995 ) (1,984,941 ) (3,282,973 ) (116,915 ) Gain on disposal of subsidiaries (Note 30) - - 802,753 28,588 Foreign exchange gains (losses), net (1,015,615 ) 1,125,681 1,005,374 35,805 Gain on disposal of investments accounted for using the equity method (Note 14) - - 91,297 3,251 Impairment losses on financial assets (Note 14) (521,010 ) (400,201 ) - - Others - (8,025 ) - - $ 7,874,273 $ 2,683,989 $ 1,827,576 $ 65,085
Summary of Finance Costs	d. Finance costs For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Interest on lease liabilities $ - $ 88,742 $ 88,026 $ 3,135 Interest on borrowings and bonds payable 3,597,932 4,211,541 3,498,999 124,608 Total interest expense for financial liabilities measured at amortized cost 3,597,932 4,300,283 3,587,025 127,743 Less: Amounts included in the cost of qualifying assets Inventories related to real estate business (11,648 ) (35,713 ) (95,589 ) (3,404 ) Property, plant and equipment (50,309 ) (77,715 ) (54,208 ) (1,930 ) Investment properties (89 ) - - - 3,535,886 4,186,855 3,437,228 122,409 Other finance costs 32,355 16,540 22,283 793 $ 3,568,241 $ 4,203,395 $ 3,459,511 $ 123,202
Summary of Capitalized Borrowing Costs	Information relating to the capitalized borrowing costs was as follows: For the Year Ended December 31 2018 2019 2020 Annual interest capitalization rates Inventories related to real estate business (%) 4.35 4.35-4.85 4.20-4.75 Property, plant and equipment (%) 1.84-4.52 0.96-4.03 0.49-3.47 Investment properties (%) 1.84-2.23 - -
Summary of Depreciation and Amortization	e. Depreciation and amortization For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Property, plant and equipment $ 39,893,786 $ 45,240,667 $ 46,016,548 $ 1,638,766 Right-of-use assets - 1,055,458 946,880 33,721 Investment properties 392,667 594,110 562,260 20,023 Other intangible assets 2,402,450 3,576,606 3,733,377 132,955 Total $ 42,688,903 $ 50,466,841 $ 51,259,065 $ 1,825,465 Summary of depreciation by function Operating costs $ 37,903,050 $ 43,749,333 $ 44,017,839 $ 1,567,587 Operating expenses 2,383,403 3,140,902 3,507,849 124,923 $ 40,286,453 $ 46,890,235 $ 47,525,688 $ 1,692,510
Summary of Operating Expenses Directly Related to Investment Properties	Operating expenses directly related to investment properties For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Direct operating expenses of investment properties that generated rental income $ 1,276,751 $ 1,232,826 $ 1,121,854 $ 39,952
Summary of Employee Benefits Expense	f. Employee benefits expense For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Post-employment benefits Defined contribution plans $ 2,965,054 $ 3,148,209 $ 2,979,167 $ 106,096 Defined benefit plans 291,333 277,041 217,186 7,735 3,256,387 3,425,250 3,196,353 113,831 Equity-settled share-based payments 215,648 871,699 955,575 34,030 Other employee benefits 63,940,430 70,279,752 76,648,412 2,729,644 $ 67,412,465 $ 74,576,701 $ 80,800,340 $ 2,877,505 Summary of employee benefits expense by function Operating costs $ 45,363,170 $ 49,173,778 $ 52,526,164 $ 1,870,590 Operating expenses 22,049,295 25,402,923 28,274,176 1,006,915 $ 67,412,465 $ 74,576,701 $ 80,800,340 $ 2,877,505
Summary of Employees' Compensation and Remuneration to Directors	g. Employees’ compensation and the remuneration to directors The Articles stipulates to distribute employees’ compensation and remuneration to directors at the rates in 0.01%-1.00% and no higher than 0.75%, respectively, of net profit before income tax, employees’ compensation and remuneration to directors. For the Year Ended December 31 2019 2020 Accrual Rate (%) Accrual Amount Accrual Rate (%) Accrual Amount NT$ NT$ US$ (Note 4) Employees’ compensation 0.20 $ 34,400 0.20 $ 54,909 $ 1,955 Remuneration to directors 0.40 68,803 0.40 109,818 3,911
Summary of Appropriations of Employees' Compensation (Settled by Cash) and Remuneration to Directors	In March 2019 and 2020, the board of directors resolved the appropriations of employees’ compensation and remuneration to directors in cash for 2018 and 2019, respectively. The differences between the resolved amounts and the accrued amounts reflected in the annual consolidated financial statements for the years ended December 31, 2018 and 2019 were deemed changes in estimates. The differences were both NT$3 thousand (US$0.1 thousand) and were adjusted in net profit for each of the year ended December 31, 2019 and 2020, respectively. For Year 2018 For Year 2019 Employees’ compensation Remuneration to directors Employees’ compensation Remuneration to directors NT$ NT$ NT$ NT$ Resolved by the board of directors $ 45,430 $ 34,070 $ 34,400 $ 68,800 Recognized in the consolidated financial statements $ 45,430 $ 34,073 $ 34,400 $ 68,803

Income Tax (Tables)

Income Tax (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Major Components of Income Tax Expense	The major components of income tax were as follows: For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Current income tax In respect of the current year $ 5,207,309 $ 5,002,954 $ 6,807,882 $ 242,446 Income tax on unappropriated earnings (1,022,560 ) 19,115 680,649 24,240 Changes in estimate for prior years (103,822 ) (352,579 ) (472,512 ) (16,827 ) 4,080,927 4,669,490 7,016,019 249,859 (Continued) For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Deferred income tax In respect of the current year $ (227,327 ) $ 563,512 $ 212,338 $ 7,562 Effect of tax rate changes 657,346 54,072 - - Changes in estimate for prior years 5,696 (213,758 ) (103,021 ) (3,669 ) Effect of foreign currency exchange differences (3,273 ) (62,070 ) (8,438 ) (301 ) 432,442 341,756 100,879 3,592 Income tax expense recognized in profit or loss $ 4,513,369 $ 5,011,246 $ 7,116,898 $ 253,451 (Concluded)
Summary of Reconciliation of Income Tax Expense	A reconciliation of income tax expense calculated at the statutory rates and income tax expense recognized in profit or loss was as follows: For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Profit before income tax $ 31,937,678 $ 23,279,811 $ 35,768,798 $ 1,273,817 Income tax expense calculated at the statutory rates $ 13,540,599 $ 11,802,811 $ 16,907,904 $ 602,133 Nontaxable expense in determining taxable income 353,019 459,133 316,619 11,276 Tax-exempt income (2,515,453 ) (495,883 ) (387,212 ) (13,790 ) Additional income tax on unappropriated earnings (1,022,560 ) 19,115 680,649 24,240 Loss carry-forward and income tax credits currently used (971,124 ) (898,198 ) (1,191,387 ) (42,428 ) Remeasurement of deferred income tax assets, net (4,776,271 ) (5,588,335 ) (8,650,569 ) (308,069 ) Changes in estimate for prior periods (103,822 ) (352,579 ) (472,512 ) (16,827 ) Unrecognized deductible temporary differences - - (138,890 ) (4,946 ) Withholding tax 8,981 65,182 52,296 1,862 Income tax expense recognized in profit or loss $ 4,513,369 $ 5,011,246 $ 7,116,898 $ 253,451
Summary of Income Tax Recognized Directly in Equity	b. Income tax recognized directly in equity For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Deferred income tax Related to employee share options $ (1,099 ) $ 1,404 $ (1,159 ) $ (41 )
Summary of Income Tax Recognized in Other Comprehensive Income	c. Income tax recognized in other comprehensive income For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Deferred income tax Related to remeasurement of defined benefit plans $ 55,346 $ 74,308 $ 114,559 $ 4,080 Unrealized loss on equity instruments at fair value through other comprehensive income - (78,124 ) (237,460 ) (8,457 ) Effect of tax rate changes 70,755 - - - Income tax recognized in other comprehensive income $ 126,101 $ (3,816 ) $ (122,901 ) $ (4,377 )
Summary of Current Tax Assets and Liabilities	d. Current tax assets and liabilities December 31 2019 2020 NT$ NT$ US$ (Note 4) Current tax assets Tax refund receivable $ 90,569 $ 303,265 $ 10,800 Prepaid income tax 462,523 399,555 14,229 $ 553,092 $ 702,820 $ 25,029 Current tax liabilities Income tax payable $ 4,858,578 $ 6,514,502 $ 231,998
Summary of Movements of Deferred Tax Assets and Deferred Tax Liabilities	The movements of deferred tax assets and deferred tax liabilities were as follows: For the year ended December 31, 2018 Balance at January 1 Adjustment on initial Application of IFRS 15 Recognized in Profit or Loss Recognized in Other Comprehensive Income Recognized in Equity Exchange Differences Acquisitions Through Business Combinations Balance at December 31 NT$ NT$ NT$ NT$ NT$ NT$ NT$ NT$ Deferred tax assets (liabilities) Temporary differences Property, plant and equipment $ (3,879,066 ) $ - $ (600,229 ) $ - $ - $ (21,146 ) $ (45,873 ) $ (4,546,314 ) Defined benefit obligation 780,240 - (131,687 ) 126,101 - 27,884 262,286 1,064,824 FVTPL financial instruments (104,903 ) - 284,659 - - (137 ) 27,402 207,021 Others 1,028,409 (97,358 ) (26,147 ) - (1,099 ) 74,327 294,540 1,272,672 (2,175,320 ) (97,358 ) (473,404 ) 126,101 (1,099 ) 80,928 538,355 (2,001,797 ) Loss carry-forward 681,441 - (50,059 ) - - 28,293 12,600 672,275 Investment credits 534,213 - 91,021 - - 5,932 - 631,166 $ (959,666 ) $ (97,358 ) $ (432,442 ) $ 126,101 $ (1,099 ) $ 115,153 $ 550,955 $ (698,356 ) For the year ended December 31, 2019 Balance at January 1 Recognized in Profit or Loss Recognized in Other Comprehensive Income Recognized in Equity Exchange Differences Acquisitions through Business Combinations Balance at December 31 NT$ NT$ NT$ NT$ NT$ NT$ NT$ Deferred tax assets (liabilities) Temporary differences Property, plant and equipment $ (4,546,314 ) $ (80,593 ) $ - $ - $ (17,949 ) $ (16,917 ) $ (4,661,773 ) Defined benefit obligation 1,064,824 (57,746 ) 74,308 - (2,803 ) - 1,078,583 FVTPL financial instruments 207,021 43,285 - - 9 - 250,315 Others 1,272,672 6,148 (78,124 ) 1,404 (21,763 ) 8,184 1,188,521 (2,001,797 ) (88,906 ) (3,816 ) 1,404 (42,506 ) (8,733 ) (2,144,354 ) Loss carry-forward 672,275 (166,128 ) - - (12,203 ) 48,837 542,781 Investment credits 631,166 (86,722 ) - - (7,404 ) - 537,040 $ (698,356 ) $ (341,756 ) $ (3,816 ) $ 1,404 $ (62,113 ) $ 40,104 $ (1,064,533 ) For the year ended December 31, 2020 Balance at January 1 Recognized in Profit or Loss Recognized in Other Comprehensive Income Recognized in Equity Exchange Differences Acquisitions through Business Combinations Disposal of Subsidiaries Balance at December 31 NT$ NT$ NT$ NT$ NT$ NT$ NT$ NT$ Deferred tax assets (liabilities) Temporary differences Property, plant and equipment $ (4,661,773 ) $ (422,833 ) $ - $ - $ 43,364 $ 21,875 $ (13,982 ) $ (5,033,349 ) Defined benefit obligation 1,078,583 (36,633 ) 114,559 - 1,005 212,941 - 1,370,455 FVTPL financial instruments 250,315 (135,103 ) - - (74 ) 2,085 (11,281 ) 105,942 Others 1,188,521 624,442 (237,460 ) (1,159 ) (42,771 ) 114,036 (119,564 ) 1,526,045 (2,144,354 ) 29,873 (122,901 ) (1,159 ) 1,524 350,937 (144,827 ) (2,030,907 ) Loss carry-forward 542,781 (44,651 ) - - (915 ) 183,045 (152,594 ) 527,666 Investment credits 537,040 (86,100 ) - - (21,559 ) - - 429,381 $ (1,064,533 ) $ (100,878 ) $ (122,901 ) $ (1,159 ) $ (20,950 ) $ 533,982 $ (297,421 ) $ (1,073,860 ) Balance at January 1 Recognized in Profit or Loss Recognized in Other Comprehensive Income Recognized in Equity Exchange Differences Acquisitions through Business Combinations Disposal of Subsidiaries Balance at December 31 US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) Deferred tax assets (liabilities) Temporary differences Property, plant and equipment $ (166,018 ) $ (15,058 ) $ - $ - $ 1,544 $ 779 $ (498 ) $ (179,251 ) Defined benefit obligation 38,411 (1,305 ) 4,080 - 36 7,583 - 48,805 FVTPL financial instruments 8,914 (4,811 ) - - (3 ) 74 (402 ) 3,772 Others 42,328 22,238 (8,457 ) (41 ) (1,523 ) 4,061 (4,258 ) 54,348 (76,365 ) 1,064 (4,377 ) (41 ) 54 12,497 (5,158 ) (72,326 ) Loss carry-forward 19,330 (1,590 ) - - (33 ) 6,519 (5,434 ) 18,792 Investment credits 19,125 (3,066 ) - - (768 ) - - 15,291 $ (37,910 ) $ (3,592 ) $ (4,377 ) $ (41 ) $ (747 ) $ 19,016 $ (10,592 ) $ (38,243 )
Summary of Unrecognized Deferred Tax Assets Related to Loss Carry-forward, Investment Credits and Deductible Temporary Differences	December 31 2019 2020 NT$ NT$ US$ (Note 4) Loss carry-forward $ 966,783 $ 1,497,056 $ 53,314 Investment credits 51,217 49,611 1,767 Deductible temporary differences 446,754 377,242 13,434 $ 1,464,754 $ 1,923,909 $ 68,515
Summary of Unused Loss Carry-forward	As of December 31, 2020, the unused loss carry-forward comprised of: Expiry Year NT$ US$ (Note 4) 2021 $ 79,849 $ 2,844 2022 140,029 4,987 2023 192,607 6,859 2024 172,337 6,137 2025 and thereafter 1,439,900 51,279 $ 2,024,722 $ 72,106
Summary of Unused Investment Credits	As of December 31, 2020, unused investment credits comprised of: Tax Credit Source Remaining Creditable Amount Expiry Year NT$ US$ (Note 4) Purchase of machinery and equipment $ 405,188 $ 14,430 2027 Others 73,804 2,628 2026 and thereafter $ 478,992 $ 17,058
Summary of Projects were Exempted From Income Tax	As of December 31, 2020, profits attributable to the following expansion projects were exempted from income tax for a 5-year pe r d Tax-exemption Period Construction and expansion of ASE Test Inc. in 2009 2018.01-2022.12

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Earnings and Weighted Average Number of Ordinary Shares Outstanding in Computation of Earnings Per Share	The earnings and weighted average number of ordinary shares outstanding in the computation of earnings per share were as follows: Net profit for the year For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Profit for the year attributable to owners of the Company $ 26,220,721 $ 17,060,591 $ 26,970,580 $ 960,490 Effect of potentially dilutive ordinary shares: Employee share options issued by subsidiaries (418,295 ) (385,865 ) (521,073 ) (18,557 ) Earnings used in the computation of diluted earnings per share $ 25,802,426 $ 16,674,726 $ 26,449,507 $ 941,933 Weighted average number of ordinary shares outstanding For the Year Ended December 31 2018 2019 2020 Weighted average number of ordinary shares in computation of basic earnings per share 4,245,247 4,251,964 4,265,732 Effect of potentially dilutive ordinary shares: From employee share options 5,103 10,232 22,086 (Continued) For the Year Ended December 31 2018 2019 2020 From employees’ compensation 779 570 815 Weighted average number of ordinary shares in computation of diluted earnings per share 4,251,129 4,262,766 4,288,633

Share-based Payment Arrangeme_2

Share-based Payment Arrangements (Tables)	12 Months Ended
	Dec. 31, 2020
Statement [LineItems]
Summary of Information About Restricted Shares	Information about USISH’s outstanding restricted shares at each balance sheet date was as follows: Range of Exercise Price Per Share (RMB) Remaining Contractual Life (Years) December 31, 2019 2019 restricted shares 13.3 4.3 December 31, 2020 2019 restricted shares 13.2 3.3 2020 restricted shares - 1.7
ASE Inc. option plans [member]
Statement [LineItems]
Summary of Information About Share Options	Information about the share option plans that ASE granted for the period from January 1, 2018 through April 29, 2018 was as follows: For the Period from January 1, 2018 through April 29, 2018 Number of Options (In Thousands) Weighted Average Exercise Price Per Share (NT$) Balance, beginning of period 135,961 $ 30.2 Options forfeited (1,692 ) 36.3 Options exercised (20,557 ) 26.0 Options transferred to the Company in accordance with the joint share exchange agreement (113,712 ) 30.9 Balance, end of period - - Information about the share option plans that the Company granted and assumed for the period from April 30, 2018 through December 31, 2018 and for the years ended December 31, 2019 and 2020 were as follows: For the Period from For the Year Ended December 31 December 31, 2018 2019 2020 Weighted Weighted Weighted Average Average Average Number of Exercise Number of Exercise Number of Exercise Options Price Options Price Options Price (In Per Share (In Per Share (In Per Share Thousands) (NT$) Thousands) (NT$) Thousands) (NT$) Balance, beginning of period - $ - 183,814 $ 58.1 170,786 $ 57.0 Options assumed on April 30, 2018 56,856 61.7 - - - - Options granted 131,863 56.4 - - - - Options expired - - - - (1,006 ) 40.8 Options forfeited (1,582 ) 71.5 (4,214 ) 61.8 (3,949 ) 58.0 Options exercised (3,323 ) 43.6 (8,814 ) 48.4 (21,064 ) 49.2 Balance, end of period 183,814 58.1 170,786 57.0 144,767 56.9 Options exercisable, end of period 36,354 58.1 33,822 63.5 67,388 61.4 Fair value of options granted (NT$) $ 16.28-19.12 $ - $ - The weighted average share prices at exercise dates of share options for the period from January 1, 2018 to April 29, 2018, the period from April 30, 2018 to December 31, 2018, and the year ended December 31, 2019 and 2020 were NT$41.0, NT$68.5, NT$69.3 and NT$68.5 (US$2.4), respectively.
Summary of Outstanding Share Options	Information about the outstanding share options that the Company granted and assumed at each balance sheet date was as follows: Range of Exercise Price Per Share (NT$) Weighted Average Remaining Contractual Life (Years) December 31, 2019 ASE 4 th $ 40.8-45.2 0.5 ASE 5 th 73.0 5.7 The Company 1 st 54.4 8.9 December 31, 2020 ASE 4 th 45.2 0.3 ASE 5 th 73.0 4.7 The Company 1 st 52.9 7.9
USIE option plans [member]
Statement [LineItems]
Summary of Information About Share Options	Information about share options was as follows: For the Year Ended December 31 2018 2019 2020 Weighted Weighted Weighted Number of Average Exercise Number of Average Exercise Number of Average Exercise Options Price Options Price Options Price (In Per Share (In Per Share (In Per Share Thousands) (US$) Thousands) (US$) Thousands) (US$) Balance at January 1 25,556 $ 2.2 16,711 $ 2.1 8,349 $ 2.3 Options forfeited - - - - (7 ) 2.9 Options exercised (8,845 ) 2.2 (8,362 ) 2.0 (8,342 ) 2.3 Balance at December 31 16,711 2.1 8,349 2.3 - - Options exercisable, end of year 16,711 2.1 8,349 2.3 - -
Summary of Outstanding Share Options	Information about USIE’s outstanding share options at each balance sheet date was as follows: Range of Exercise Price Per Share (US$) Weighted Average Remaining Contractual Life (Years) December 31, 2019 1 st $ 1.5 1.0 3 rd 2.9 1.4
Trinomial tree model [member]
Statement [LineItems]
Summary of Inputs Related to Fair Value of Share Options	For the fair values at the grant date of USISH’s 2019 and 2020 plans, the share options plans were measured by using the trinomial tree model, while the restricted shares plans were measured by using the Black-Scholes Option Pricing Model incorporating the effect of the lock-up period. The inputs to the models were as follows: Share option plan 2019 share options plan 2020 share options plan Share price at the grant date RMB15.84 per share RMB21.55 per share Exercise price RMB13.34 per share RMB21.65 per share Expected volatility (%) 45.07-51.80 48.14-53.57 Expected lives (years) 3-5 2.2-4.2 Expected dividend yield - - Risk free interest rate (%) 2.80-2.97 2.80-2.99 Restricted share plan 2019 restricted shares plan 2019 restricted shares plan amended in 2020 2020 restricted shares plan Share price at the grant date RMB16.30 per share RMB16.60 per share RMB24.30 per share Exercise price RMB13.34 per share RMB13.34 per share (Note) Expected volatility (%) 47.77 57.21 56.97 Lock-up periods (years) 1 1 1.3 Expected dividend yield - - - Risk free interest rate (%) 2.70 1.55 2.63
USISH option plans [member]
Statement [LineItems]
Summary of Information About Share Options	Information about share options was as follows: For the Year Ended December 31 2018 2019 2020 Number of Exercise Number of Exercise Number of Exercise Options Price Options Price Options Price (In Per Share (In Per Share (In Per Share Thousands) (RMB) Thousands) (RMB) Thousands) (RMB) Balance at January 1 22,341 $ 15.5 21,537 $ 15.5 35,077 $ 14.5 Options granted - - 17,167 13.3 1,140 21.7 Options forfeited (804) 15.5 (463 ) 15.4 (636 ) 14.0 Options exercised - - (3,164 ) 15.5 (4,315 ) 15.5 Balance at December 31 21,537 15.5 35,077 14.5 31,266 14.6 Options exercisable, end of year 12,884 15.5 13,694 15.5 13,416 15.5 Fair value of options granted (RMB) - $ 6.27-8.35 $ 7.03-8.93
Summary of Outstanding Share Options	Information about USISH’s outstanding share options at each balance sheet date was as follows: Range of Exercise Price Per Share (RMB) Remaining Contractual Life (Years) December 31, 2019 2015 share options $ 15.5 5.9 2019 share options 13.3 4.9 December 31, 2020 2015 share options 15.5 4.9 2019 share options 13.3 3.9 2020 share options 21.7 3.9
Summary of Information About Restricted Shares	Information about restricted shares was as follows: For the Year Ended December 31 2019 2020 Number of Exercise Number of Exercise Options Price Options Price (In Per Share (In Per Share Thousands) (RMB) Thousands) (RMB) Balance at January 1 - $ - 6,156 $ 13.3 Options granted 6,156 13.3 672 4.9 Options exercised - - (1,281 ) 13.2 Balance at December 31 6,156 13.3 5,547 12.2 Options exercisable, end of year - - - - Fair value of options granted (RMB) $ 13.47 $ 18.55

Business Combinations (Tables)

Business Combinations (Tables)	12 Months Ended
	Dec. 31, 2020
Statement [LineItems]
Summary of Subsidiary Acquired	Principal Activity Date of Acquisition Proportion of Voting Equity Interests Acquired (%) Consideration Transferred NT$ US$ (Note 4) SPIL Engaged in the assembly, testing and turnkey services of integrated circuits April 30, 2018 100.00 $ 168,440,585 AMPI Engaged in the April 30, 2019 50.97 $ 250,000 ASEEE Engaged in the production of embedded substrate April 26, 2019 51.00 -
Summary of Assets Acquired and Liabilities Assumed at the Date of Acquisition	c. Assets acquired and liabilities assumed at the date of acquisition SPIL AMPI ASEEE USIPL FAFG NT$ NT$ NT$ NT$ NT$ US$ (Note 4) Assets Cash and cash equivalents $ 20,088,970 $ 349,496 $ 23,197 $ 108,718 $ 2,349,164 $ 83,660 Trade and other receivables 15,840,649 371,144 5,732 58,713 4,434,296 157,917 Inventories 5,693,644 403,887 11,033 229 4,763,237 169,631 Property, plant and equipment 81,985,622 683,207 1,361,572 525,048 1,730,783 61,637 Intangible assets 31,354,386 128,900 290,757 11,704 642,838 22,893 Others 24,945,922 237,766 317,888 99,112 1,798,564 64,051 Liabilities Trade and other payables (19,755,598 ) (224,295 ) (133,278 ) (217,887 ) (4,575,720 ) (162,953 ) Borrowings and bonds payables (24,157,174 ) (951,519 ) (1,371,395 ) (190,737 ) (356,417 ) (12,693 ) Others (3,963,201 ) (148,723 ) (290,273 ) (63,708 ) (2,588,277 ) (92,175 ) Fair value of identifiable net assets acquired $ 132,033,220 $ 849,863 $ 215,233 $ 331,192 $ 8,198,468 $ 291,968
Summary of Goodwill Recognized on Acquisition	e. Goodwill recognized on acquisitions SPIL AMPI ASEEE USIPL FAFG NT$ NT$ NT$ NT$ NT$ US$ (Note 4) Consideration transferred $ 168,440,585 $ 250,000 $ - $ 313,057 $ 12,829,372 $ 456,887 Add: Fair value of investments previously owned - 315,925 117,609 - - - Add: Non-controlling interests 3,582,866 416,716 105,464 142,494 (5,635 ) (201 ) Less: Fair value of identifiable net assets acquired (132,033,220 ) (849,863 ) (215,233 ) (331,192 ) (8,198,468 ) (291,968 ) Goodwill recognized on acquisition $ 39,990,231 $ 132,778 $ 7,840 $ 124,359 $ 4,625,269 $ 164,718
Summary of Net Cash Outflow on Acquisition of Subsidiaries	f. Net cash outflow (inflow) on acquisition of subsidiaries SPIL AMPI ASEEE USIPL FAFG NT$ NT$ NT$ NT$ NT$ US$ (Note 4) Consideration paid in cash $ 168,440,585 $ 250,000 $ - $ 313,057 $ 11,094,802 $ 395,114 Less: Payable for consideration representing the ordinary shares originally held by ASE (53,109,760 ) - - - - - Less: Cash and cash equivalent acquired (20,088,970 ) (349,496 ) (23,197 ) (108,718 ) (2,349,164 ) (83,660 ) Net cash outflow (inflow) on acquisition of subsidiaries $ 95,241,855 $ (99,496 ) $ (23,197 ) $ 204,339 $ 8,745,638 $ 311,454
Summary of Impact of Acquisitions by Comprehensive Income	g. Impact of acquisitions on the results of the Group The results of operations since the acquisition date were included in the consolidated statements of comprehensive income and were as follows: SPIL (For the Period from April 30, 2018 through December 31, 2018) AMPI (For the Period from April 30, 2019 through December 31, 2019) ASEEE (For the Period from April 26, 2019 through December 31, 2019) USIPL (For the Period from October 31, 2019 through December 31, 2019) FAFG (For the Period from December 1, 2020 through December 31, 2020) NT$ NT$ NT$ NT$ NT$ US$ (Note 4) Operating revenue $ 61,247,727 $ 704,243 $ (1,159 ) $ 39,080 $ 2,043,440 $ 72,772 Net profit (loss) $ 7,627,382 $ (217,163 ) $ (469,598 ) $ (11,995 ) $ 91,179 $ 3,247
Summary of Consideration Transferred in business combination	b. Consideration Transferred SPIL AMPI ASEEE USIPL FAFG NT$ NT$ NT$ NT$ NT$ US$ (Note 4) Cash $ 168,440,585 $ 250,000 $ - $ 313,057 $ 10,800,558 $ 384,635 Equity instrument issued - - - - 1,734,570 61,772 Contingent consideration arrangement - - - - 294,244 10,479 Fair value of identifiable net assets acquired $ 168,440,585 $ 250,000 $ - $ 313,057 $ 12,829,372 $ 456,886

Disposal of Subsidiaries (Table

Disposal of Subsidiaries (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Analysis of Assets and Liabilities on Date Control was Lost	a. Analysis of assets and liabilities on the date control was lost NT$ US$ (Note 4) Current Assets Cash and cash equivalent $ 200,347 $ 7,135 Trade receivables, net 318,425 11,340 Inventories 239,865 8,542 Other current assets 111,913 3,985 Non-Current Assets Property, plant and equipment 7,546,413 268,747 Right-of-use assets 812,861 28,948 Deferred tax assets 298,217 10,620 Other non-current assets 43,482 1,548 Current Liabilities Trade and other payables (1,739,330 ) (61,942 ) Current portion of long-term borrowings (1,746,000 ) (62,179 ) Other current liabilities (24,564 ) (875 ) NT$ US$ (Note 4) Non-Current Liabilities Long-term borrowings (2,947,682 ) (104,974 ) Deferred tax liabilities (796 ) (28 ) Net assets disposed of $ 3,113,151 $ 110,867
Summary of Gain on Disposal of Subsidiaries	b. Gain on disposal of subsidiarie s NT$ US$ (Note 4) Total consideration (paid in cash) $ 4,078,844 $ 145,258 Net assets disposed of (3,113,151 ) (110,867 ) Reclassification of accumulated exchange difference from equity to profit or loss due to the loss of control over SF (162,940 ) (5,803 ) Gain on disposal of SF $ 802,753 $ 28,588
Summary of Net Cash Inflow on Disposal of Susbsidiaries	c. Net cash inflow on disposals of subsidiaries NT$ US$ (Note 4) Consideration received in cash and cash equivalents $ 4,078,844 $ 145,258 Less: Cash and cash equivalent balances disposed of (200,347 ) (7,135 ) Other receivables (the outstanding receivables of consideration, net of relevant expenditure) (161,458 ) (5,750 ) $ 3,717,039 $ 132,373

Cash Flows Information (Tables)

Cash Flows Information (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Non-cash Investing Activities	a. Non-cash investing activities In addition to other notes, the Group entered into the following investing activities which include both cash and non-cash items for the years ended December 31, 2018, 2019 and 2020: For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Payments for property, plant and equipment Purchase of property, plant and equipment $ 39,092,238 $ 63,073,887 $ 59,024,201 $ 2,102,001 Increase in other non-current assets 402,255 68,560 78,291 2,788 For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Decrease (increase) in other payables $ 1,942,259 $ (6,254,579 ) $ 3,029,162 $ 107,876 Capitalized borrowing costs (50,309 ) (77,715 ) (54,208 ) (1,930 ) $ 41,386,443 $ 56,810,153 $ 62,077,446 $ 2,210,735 Proceeds from disposal of property, plant and equipment Consideration from disposal of property, plant and equipment $ 1,133,435 $ 441,444 $ 5,184,925 $ 184,648 Decrease (increase) in other receivables (5,791 ) 7,495 (735,812 ) (26,204 ) $ 1,127,644 $ 448,939 $ 4,449,113 $ 158,444 Payments for investment properties Purchase of investment properties $ 125,853 $ 2,532 $ - $ - Capitalized borrowing costs (89 ) - - - $ 125,764 $ 2,532 $ - $ - Payments for other intangible assets Purchase of other intangible assets $ 537,659 $ 1,350,908 $ 982,655 $ 34,995 Decrease in other payables 40,106 60,160 - - $ 577,765 $ 1,411,068 $ 982,655 $ 34,995
Change in Liabilities Arising From Financing Activities	b. Changes in liabilities arising from financing activities For the year ended December 31, 2018 Short-term Borrowings Bonds Payable Long-term Borrowings Total NT$ NT$ NT$ NT$ Balance at January 1, 2018 $ 17,962,471 $ 23,142,780 $ 35,406,628 $ 76,511,879 Net financing cash flows 22,327,813 (6,185,600 ) 85,510,959 101,653,172 Non-cash changes Acquisition through business combinations 3,619,858 4,457,191 16,080,125 24,157,174 Bonds conversion - (4,457,191 ) - (4,457,191 ) Reclassification for the application of IFRS 9 (1,301,994 ) - - (1,301,994 ) Amortization of issuance cost - 28,756 188,217 216,973 Effects of foreign currency exchange 655,321 - 712,400 1,367,721 Balance at December 31, 2018 $ 43,263,469 $ 16,985,936 $ 137,898,329 $ 198,147,734 For the year ended December 31, 2019 Short-term Borrowings (including financial liabilities for hedging) Bonds Payable Long-term Borrowings Lease Liabilities Total NT$ NT$ NT$ NT$ NT$ Balance at January 1, 2019 $ 47,163,103 $ 16,985,936 $ 137,898,329 $ 6,084,729 $ 208,132,097 Net financing cash flows (4,683,142 ) 19,279,033 1,144,731 (636,556 ) 15,104,066 Interest under operating activities - - - 1,766 1,766 Non-cash changes Lease liabilities - - - 536,216 536,216 Acquisition through business combinations (Note 29) 656,820 245,664 1,523,968 81,649 2,508,101 Amortization of issuance cost - 11,522 189,151 - 200,673 Lease modifications - - - (239,321 ) (239,321 ) Short-term borrowings transferred to long-term borrowings (1,499,000 ) - 1,499,000 - - Effects of foreign currency exchange (1,065,452 ) - (1,176,581 ) (19,559 ) (2,261,592 ) Balance at December 31, 2019 $ 40,572,329 $ 36,522,155 $ 141,078,598 $ 5,808,924 $ 223,982,006 For the year ended December 31, 2020 Short-term Borrowings (including financial liabilities for hedging) Bonds Payable Long-term Borrowings (including financial liabilities for hedging) Lease Liabilities Total NT$ NT$ NT$ NT$ NT$ Balance at January 1, 2020 $ 40,572,329 $ 36,522,155 $ 141,078,598 $ 5,808,924 $ 223,982,006 Net financing cash flows (1,502,323 ) 19,717,149 (26,500,139 ) (844,357 ) (9,129,670 ) Interest under operating activities - - - 111 111 Rent expense under operating activities - - - (7,729 ) (7,729 ) Non-cash changes Lease liabilities - - - 584,642 584,642 Amortization of issuance cost - 14,250 156,982 - 171,232 Lease modifications - - - (289,687 ) (289,687 ) Short-term borrowings transferred to long-term borrowings (3,850,000 ) - 3,850,000 - - Adjustments for government subsidy - - 41,650 - 41,650 Acquisition of subsidiaries (Note 29) 356,417 - - 633,606 990,023 Disposal of subsidiaries (Note 30) - - (4,693,682 ) (670 ) (4,694,352 ) Effects of foreign currency exchange (978,565 ) - (1,542,685 ) (9,010 ) (2,530,260 ) Balance at December 31, 2020 $ 34,597,858 $ 56,253,554 $ 112,390,724 $ 5,875,830 $ 209,117,966 Short-term Borrowings (including financial liabilities for hedging) Bonds Payable Long-term Borrowings (including financial liabilities for hedging) Lease Liabilities Total US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) Balance at January 1, 2020 $ 1,444,883 $ 1,300,647 $ 5,024,168 $ 206,871 $ 7,976,569 Net financing cash flows (53,502 ) 702,178 (943,737 ) (30,070 ) (325,131 ) Interest under operating activities - - - 4 4 Rent expense under operating activities - - - (275 ) (275 ) Non-cash changes Lease liabilities - - - 20,821 20,821 Amortization of issuance cost - 507 5,591 - 6,098 Lease modifications - - - (10,316 ) (10,316 ) Short-term Borrowings (including financial liabilities for hedging) Bonds Payable Long-term Borrowings (including financial liabilities for hedging) Lease Liabilities Total US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) Short-term borrowings transferred to long-term borrowings (137,108 ) - 137,108 - - Adjustments for government subsidy - - 1,483 - 1,483 Acquisition of subsidiaries (Note 29) 12,693 - - 22,564 35,257 Disposal of subsidiaries (Note 30) - - (167,154 ) (24 ) (167,178 ) Effects of foreign currency exchange (34,849 ) - (54,939 ) (322 ) (90,110 ) Balance at December 31, 2020 $ 1,232,117 $ 2,003,332 $ 4,002,520 $ 209,253 $ 7,447,222

Financial Instruments (Tables)

Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2020
Statement [LineItems]
Summary of Fair Value of Financial Instruments	The carrying amounts and fair value of bonds payable as of December 31, 2019 and 2020 were as follows: Carrying Amount Fair Value NT$ US$ (Note 4) NT$ US$ (Note 4) December 31, 2019 $ 36,522,155 $ 36,766,117 December 31, 2020 56,253,554 $ 2,003,332 56,448,769 $ 2,010,284
Summary of Financial Assets Measured at Level 3 Fair Value	2) Reconciliation of Level 3 fair value measurements of financial assets For the year ended December 31, 2019 Financial Assets at FVTPL Financial Assets at FVTOCI Financial Assets Equity Instruments Equity Instruments Debt Instruments Total NT$ NT$ NT$ NT$ Balance at January 1 $ 475,123 $ 580,399 $ 1,016,924 $ 2,072,446 Recognized in profit or loss 3,431 - - 3,431 Recognized in other comprehensive income 　Included in unrealized losses on financial assets at FVTOCI - (216,121 ) (2,052 ) (218,173 ) 　Effects of foreign currency exchange (14,368 ) (5,695 ) - (20,063 ) Net increase in trade receivables - - 3,171,205 3,171,205 Trade receivables factoring - - (1,141,515 ) (1,141,515 ) Purchases 541,528 409,985 - 951,513 Disposals - (12,665 ) - (12,665 ) Balance at December 31 $ 1,005,714 $ 755,903 $ 3,044,562 $ 4,806,179 For the year ended December 31, 2020 Financial Assets at FVTPL Financial Assets at FVTOCI Financial Assets Equity Instruments Debt Instruments Equity Instruments Debt Instruments Total NT$ NT$ NT$ NT$ NT$ Balance at January 1 $ 1,005,714 $ - $ 755,903 $ 3,044,562 $ 4,806,179 Recognized in profit or loss (17,941 ) - - - (17,941 ) Recognized in other comprehensive income Includevd in unrealized losses on financial assets at FVTOCI - - (149,856 ) (2,136 ) (151,992 ) Effects of foreign currency exchange (15,455 ) - (15,562 ) - (31,017 ) Net increase in trade receivables - 370,110 - 5,635,706 6,005,816 Trade receivables factoring - (370,110 ) - (7,038,983 ) (7,409,093 ) Purchases 893,234 - 259,168 - 1,152,402 Disposals (329,370 ) - (121,255 ) - (450,625 ) Exercise of call option (25,988 ) - - - (25,988 ) Balance at December 31 $ 1,510,194 $ - $ 728,398 $ 1,639,149 $ 3,877,741 Financial Assets at FVTPL Financial Assets at FVTOCI Financial Assets Equity Instruments Debt Instruments Equity Instruments Debt Instruments Total US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) Balance at January 1 $ 35,816 $ - $ 26,920 $ 108,424 $ 171,160 Recognized in profit or loss (639 ) - - - (639 ) Recognized in other comprehensive income Included in unrealized losses on financial assets at FVTOCI - - (5,337 ) (76 ) (5,413 ) Effects of foreign currency exchange (550 ) - (555 ) - (1,105 ) Net increase in trade receivables - 13,181 - 200,702 213,883 Trade receivables factoring - (13,181 ) - (250,676 ) (263,857 ) Purchases 31,810 - 9,230 - 41,040 Disposals (11,730 ) - (4,318 ) - (16,048 ) Exercise of call option (926 ) - - - (926 ) Balance at December 31 $ 53,781 $ - $ 25,940 $ 58,374 $ 138,095
Summary of Categories of Financial Instruments	c. Categories of financial instruments December 31 2019 2020 NT$ NT$ US$ (Note 4) Financial assets FVTPL Mandatorily at FVTPL $ 5,288,996 $ 6,135,793 $ 218,511 Measured at amortized cost (Note 1) 139,668,804 147,521,583 5,253,618 FVTOCI Equity instruments 755,903 728,398 25,940 Debt instruments 1,014,872 1,012,736 36,066 Trade receivables, net 2,029,690 626,413 22,308 Financial liabilities FVTPL Held for trading 973,571 1,537,208 54,744 Financial liabilities for hedging 3,233,301 11,188,244 398,442 Measured at amortized cost (Note 2) 310,187,110 304,737,749 10,852,485 Note 1: The balances included financial assets measured at amortized cost which comprised cash and cash equivalents, trade and other receivables and other financial assets. Note 2: The balances included financial liabilities measured at amortized cost which comprised short-term borrowings, trade and other payables, bonds payable and long-term borrowings.
Summary of Detailed Information About Hedged	December 31, 2019 Hedging Instrument/ Line item in Carrying Amount Hedged Items Balance sheet Asset Liability NT$ NT$ Fair value hedge Borrowings denominated in foreign currencies/ Financial assets at FVTPL Financial liabilities for hedging - current $ - $ 3,233,301 December 31, 2020 Hedging Instrument/ Line item in Carrying Amount Hedged Items Balance sheet Asset Liability NT$ US$ (Note 4) NT$ US$ (Note 4) Fair value hedge Borrowings denominated in foreign currencies/ Financial assets at FVTPL Financial liabilities for hedging - current $ - $ - $ 3,307,018 $ 117,771 Hedge of net investment in foreign operation Financial liabilities for hedging - current - - 1,970,307 70,168 Hedge of net investment in foreign operation Financial liabilities for hedging - non-current - - 5,910,919 210,503
Summary of Detailed Information About Hedged Items	Change in Value Used for Calculating Hedge Ineffectiveness Accumulated Gains or Losses in Other Equity Carrying Amount of Hedged Item in Fair Value Hedge Accumulated Amount of Fair Value Hedge Adjustments on Hedged Item Hedging Instrument/ Hedged Item Hedging Instrument Hedged Item Continuing Hedges Hedge Accounting No Longer Applied Asset Asset NT$ NT$ NT$ NT$ NT$ NT$ Fair value hedge Borrowings denominated in foreign currencies/ Financial assets at FVTPL $ 71,743 $ (71,743 ) $ - $ - $ 2,791,574 $ 15,625 Change in Value Used for Calculating Hedge Ineffectiveness Accumulated Gains or Losses in Other Equity Carrying Amount of Hedged Item in Fair Value Hedge Accumulated Amount of Fair Value Hedge Adjustments on Hedged Item Hedging Instrument/ Hedged Item Hedging Instrument Hedged Item Continuing Hedges Hedge Accounting No Longer Applied Asset Asset NT$ NT$ NT$ NT$ NT$ NT$ Fair value hedge Borrowings denominated in foreign currencies/ Financial assets at FVTPL $ 157,842 $ (157,842 ) $ - $ - $ 2,859,132 $ (142,217 ) Hedge of net investment in foreign operation 574,824 (574,824 ) (574,824 ) - - - Change in Value Used for Calculating Hedge Ineffectiveness Accumulated Gains or Losses in Other Equity Carrying Amount of Hedged Item in Fair Value Hedge Accumulated Amount of Fair Value Hedge Adjustments on Hedged Item Hedging Instrument/ Hedged Ite m Hedging Instrument Hedged Item Continuing Hedges Hedge Accounting No Longer Applied Asset Asset US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) Fair value hedge Borrowings denominated in foreign currencies/ Financial assets at FVTPL $ 5,621 $ (5,621 ) $ - $ - $ 101,821 $ (5,065 ) Hedge of net investment in foreign operatio n 20,471 (20,471 ) (20,471 ) - - -
Summary of Maturity Analysis for Non-derivative Financial Liabilities	December 31, 2019 On Demand or Less than 1 Month 1 to 3 Months 3 Months to 1 Year 1 to 5 Years More than 5 Years NT$ NT$ NT$ NT$ NT$ Non-derivative financial liabilities Non-interest bearing $ 35,283,757 $ 38,803,904 $ 7,989,256 $ 33,797 $ 184,338 Obligation under leases 75,388 115,297 532,747 1,536,600 4,412,859 Floating interest rate liabilities 10,740,844 6,708,303 18,868,999 133,341,087 7,190,891 Fixed interest rate liabilities 6,819,585 3,712,979 2,281,375 34,405,594 3,689,219 $ 52,919,574 $ 49,340,483 $ 29,672,377 $ 169,317,078 $ 15,477,307 December 31, 2020 On Demand or Less than 1 Month 1 to 3 Months 3 Months to 1 Year 1 to 5 Years More than 5 Years NT$ NT$ NT$ NT$ NT$ Non-derivative financial liabilities Non-interest bearing $ 43,111,390 $ 44,122,659 $ 8,223,684 $ 319,510 $ 176,536 Obligation under leases 103,734 151,921 619,908 1,779,041 4,088,301 Floating interest rate liabilities 13,792,596 8,190,076 10,214,154 102,253,481 7,999,130 Fixed interest rate liabilities 11,895,281 528,290 3,349,614 46,900,450 5,631,522 $ 68,903,001 $ 52,992,946 $ 22,407,360 $ 151,252,482 $ 17,895,489 On Demand or Less than 1 Month 1 to 3 Months 3 Months to 1 Year 1 to 5 Years More than 5 Years US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) Non-derivative financial liabilities Non-interest bearing $ 1,535,306 $ 1,571,320 $ 292,866 $ 11,379 $ 6,287 Obligation under leases 3,694 5,410 22,077 63,356 145,595 Floating interest rate liabilities 491,189 291,669 363,752 3,641,506 284,869 Fixed interest rate liabilities 423,621 18,814 119,288 1,670,244 200,553 $ 2,453,810 $ 1,887,213 $ 797,983 $ 5,386,485 $ 637,304
Summary of Maturity Analysis for Derivative Financial Instruments	On Demand or Less than 1 Month 1 to 3 Months 3 Months to 1 Year NT$ NT$ NT$ December 31, 2019 Net settled Forward exchange contracts $ (74,864 ) $ (13,246 ) $ - On Demand or Less than 1 Month 1 to 3 Months 3 Months to 1 Year NT$ NT$ NT$ Gross settled Forward exchange contracts Inflows $ 9,296,123 $ 4,420,233 $ 230,354 Outflows (9,248,333 ) (4,392,070 ) (227,848 ) 47,790 28,163 2,506 Swap contracts Inflows 10,187,215 15,025,154 34,327,100 Outflows (10,163,964 ) (15,032,603 ) (34,773,848 ) 23,251 (7,449 ) (446,748 ) $ 71,041 $ 20,714 $ (444,242 ) On Demand or Less than 1 Month 1 to 3 Months 3 Months to 1 Year Over 1 Year NT$ NT$ NT$ NT$ December 31, 2020 Net settled Forward exchange contracts $ 30,514 $ 18,429 $ - $ - Gross settled Forward exchange contracts Inflows $ 8,862,682 $ 5,565,137 $ 531,336 $ - Outflows (8,798,238 ) (5,518,153 ) (526,880 ) - 64,444 46,984 4,456 - Swap contracts Inflows 19,311,999 17,179,871 36,739,200 $ - Outflows (19,524,820 ) (17,486,997 ) (37,495,172 ) - (212,821 ) (307,124 ) (755,972 ) - Target redemption forward contracts Inflows 42,720 96,120 416,520 227,128 Outflows (44,471 ) (100,060 ) (433,595 ) (236,081 ) (1,751 ) (3,940 ) (17,075 ) (8,953 ) $ (150,128 ) $ (264,080 ) $ (768,591 ) $ (8,953 ) On Demand or Less than 1 Month 1 to 3 Months 3 Months to 1 Year Over 1 Year US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) December 31, 2020 Net settled Forward exchange contracts $ 1,087 $ 656 $ - $ - Gross settled Forward exchange contracts Inflows $ 315,623 $ 198,189 $ 18,922 $ - Outflows (313,328 ) (196,516 ) (18,763 ) - 2,295 1,673 159 - On Demand or Less than 1 Month 1 to 3 Months 3 Months to 1 Year Over 1 Year US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) Swap contracts Inflows 687,749 611,819 1,308,376 $ - Outflows (695,328 ) (622,756 ) (1,335,298 ) - (7,579 ) (10,937 ) (26,922 ) - Target redemption forward contracts Inflows 1,522 3,423 14,833 8,089 Outflows (1,584 ) (3,563 ) (15,441 ) (8,408 ) (62 ) (140 ) (608 ) (319 ) $ (5,346 ) $ (9,404 ) $ (27,371 ) $ (319 )
Summary of Disclosure of Detailed Information about Maturity Analysis of Obligation under Leases	Further information for maturity analysis of obligation under leases was as follows: Less than 1 Year 1 to 5 Years 5 to 10 Years 10 to 15 Years 15 to 20 Years More than 20 Years NT$ NT$ NT$ NT$ NT$ NT$ Obligation under leases $ 875,563 $ 1,779,041 $ 1,422,331 $ 776,735 $ 674,446 $ 1,214,789 Further information for maturity analysis of obligation under leases was as follows: Less than 1 Year 1 to 5 Years 5 to 10 Years 10 to 15 Years 15 to 20 Years More than 20 Years NT$ NT$ NT$ NT$ NT$ NT$ Obligation under leases $ 875,563 $ 1,779,041 $ 1,422,331 $ 776,735 $ 674,446 $ 1,214,789 Less than 1 Year 1 to 5 Years 5 to 10 Years 10 to 15 Years 15 to 20 Years More than 20 Years US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) US$ (Note 4) Obligation under leases $ 31,181 $ 63,356 $ 50,653 $ 27,661 $ 24,019 $ 43,262
Interest rate risk [member]
Statement [LineItems]
Summary of Interest Rate Risk	The carrying amounts of th e n December 31 2019 2020 NT$ NT$ US$ (Note 4) Fair value interest rate risk Financial liabilities $ 41,952,056 $ 56,599,417 $ 2,015,649 Cash flow interest rate risk Financial assets 46,467,663 45,489,788 1,620,007 Financial liabilities 169,709,237 131,715,366 4,690,718
Measured at fair value on a recurring basis [member]
Statement [LineItems]
Summary of Fair Value of Financial Instruments	1) Fair value hierarchy Level 1 Level 2 Level 3 Total NT$ NT$ NT$ NT$ December 31, 2019 Financial assets at FVTPL Derivative financial assets Forward exchange contracts $ - $ 104,308 $ - $ 104,308 Swap contracts - 56,561 - 56,561 Call option - - 24,556 24,556 Non-derivative financial assets Quoted ordinary shares 3,460,123 - - 3,460,123 Open-end mutual funds 662,290 - - 662,290 Private-placement funds - - 603,718 603,718 Unquoted preferred shares - - 377,440 377,440 $ 4,122,413 $ 160,869 $ 1,005,714 $ 5,288,996 Financial assets at FVTOCI Investments in equity instruments Unquoted ordinary shares $ - $ - $ 565,028 $ 565,028 Unquoted preferred shares - - 158,718 158,718 Limited partnership - - 32,157 32,157 Investments in debt instruments Unsecured subordinate corporate bonds - - 1,014,872 1,014,872 Trade receivables, net - - 2,029,690 2,029,690 $ - $ - $ 3,800,465 $ 3,800,465 Financial liabilities at FVTPL Derivative financial liabilities Swap contracts $ - $ 862,581 $ - $ 862,581 Forward exchange contracts - 110,990 - 110,990 $ - $ 973,571 $ - $ 973,571 Level 1 Level 2 Level 3 Total NT$ US$ (Note 4) NT$ US$ (Note 4) NT$ US$ (Note 4) NT$ US$ (Note 4) December 31, 2020 Financial assets at FVTPL Derivative financial assets Forward exchange contracts $ - $ - $ 122,511 $ 4,363 $ - $ - $ 122,511 $ 4,363 Swap contracts - - 99,312 3,537 - - 99,312 3,537 Non-derivative financial assets Quoted ordinary shares 4,064,438 144,745 - - - - 4,064,438 144,745 Private-placement funds - - - - 1,124,754 40,055 1,124,754 40,055 Unquoted preferred shares - - - - 385,440 13,726 385,440 13,726 Open-end mutual funds 339,338 12,085 - - - - 339,338 12,085 $ 4,403,776 $ 156,830 $ 221,823 $ 7,900 $ 1,510,194 $ 53,781 $ 6,135,793 $ 218,511 Financial assets at FVTOCI Investments in equity instruments Unquoted ordinary shares $ - $ - $ - $ - $ 567,377 $ 20,206 $ 567,377 $ 20,206 Unquoted preferred shares - - - - 151,329 5,389 151,329 5,389 Limited partnership - - - - 9,692 345 9,692 345 Investments in debt instruments Unsecured subordinate corporate bonds - - - - 1,012,736 36,066 1,012,736 36,066 Trade receivables, net - - - - 626,413 22,308 626,413 22,308 $ - $ - $ - $ - $ 2,367,547 $ 84,314 $ 2,367,547 $ 84,314 Financial liabilities at FVTPL Derivative financial liabilities Swap contracts $ - $ - $ 1,448,972 $ 51,602 $ - $ - $ 1,448,972 $ 51,602 Target redemption forward contracts - - 79,216 2,821 - - 79,216 2,821 Forward exchange contracts - - 9,020 321 - - 9,020 321 $ - $ - $ 1,537,208 $ 54,744 $ - $ - $ 1,537,208 $ 54,744

Related Party Transactions (Tab

Related Party Transactions (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Compensation to Key Management Personnel	For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Short-term employee benefits $ 1,041,216 $ 1,027,191 $ 1,264,980 $ 45,049 Post-employment benefits 3,884 2,208 2,007 72 Share-based payments 9,145 134,544 153,774 5,476 $ 1,054,245 $ 1,163,943 $ 1,420,761 $ 50,597

Assets Pledged as Collateral _2

Assets Pledged as Collateral or for Security (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Assets Pledged as Collateral or for Security	The following assets were provided as collateral for bank borrowings, tariff guarantees of imported raw materials or collateral: December 31 2019 2020 NT$ NT$ US$ (Note 4) Inventories related to real estate business $ 6,063,303 $ 10,564,873 $ 376,242 Property, plant and equipment 138,831 124,124 4,420 Investment properties 12,167,772 11,847,145 421,907 Other financial assets (including current and non-current) 637,775 460,890 16,414 $ 19,007,681 $ 22,997,032 $ 818,983

Significant Assets and Liabil_2

Significant Assets and Liabilities Denominated in Foreign Currencies (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Significant Assets and Liabilities Denominated in Foreign Currencies	The following information was aggregated by the foreign currencies other than functional currencies of the group entities and the exchange rates between foreign currencies and respective functional currencies were disclosed. The significant financial assets and liabilities denominated in foreign currencies were as follows: Foreign Currencies (In Thousand) Exchange Rate Carrying Amount (In Thousand) December 31, 2019 Monetary financial assets US$ $ 4,125,872 US$1=NT$29.98 $ 123,693,628 US$ 1,189,539 US$1=RMB6.9762 35,662,384 JPY 13,889,872 JPY1=NT$0.2760 3,833,605 JPY 771,392 JPY1=US$0.0092 212,904 Monetary financial liabilities US$ 3,823,359 US$1=NT$29.98 114,624,313 US$ 1,211,472 US$1=RMB6.9762 36,319,926 JPY 14,628,543 JPY1=NT$0.2760 4,037,478 JPY 815,929 JPY1=US$0.0092 225,197 December 31, 2020 Monetary financial assets US$ 4,269,075 US$1=NT$28.48 121,583,265 US$ 1,527,381 US$1=RMB6.5249 43,499,803 US$ 41,643 EUR1=US$0.8143 1,185,984 JPY 13,544,360 JPY1=NT$0.2763 3,742,306 JPY 1,174,208 JPY1=US$0.0097 324,434 HKD 174,765 HKD1=NT$3.6730 641,912 Monetary financial liabilities US$ 4,439,915 US$1=NT$28.48 126,448,786 US$ 1,517,568 US$1=RMB6.5249 43,220,325 US$ 20,896 EUR1=US$0.8143 595,128 JPY 13,657,967 JPY1=NT$0.2763 3,773,695 JPY 1,188,650 JPY1=US$0.0097 328,424 HKD 18,814 HKD1=NT$3.6730 69,103
Summary of Realized and Unrealized Foreign Exchange Gain (Loss)	The significant realized and unrealized foreign exchange gain (loss) were as follows: For the Year Ended December 31 2018 2019 2020 Functional Currencies Exchange Rate Net Foreign Exchange Loss Exchange Rate Net Foreign Exchange Gain (Loss) Exchange Rate Net Foreign Exchange Gain (Loss) NT$ NT$ NT$ US$ (Note 4) US$ US$1=NT$30.715 $ (67,476 ) US$1=NT$29.98 $ (84,177 ) US$1=NT$28.48 $ (143,804 ) $ (5,121 ) NT$ (849,234 ) 1,203,823 1,382,067 49,219 RMB RMB1=NT$4.4753 (120,005 ) RMB1=NT$4.2975 14,055 RMB1=NT$4.3648 (181,624 ) (6,468 ) $ (1,036,715 ) $ 1,133,701 $ 1,056,639 $ 37,630

Operating Segments Information

Operating Segments Information (Tables)	12 Months Ended
	Dec. 31, 2020
Text block [abstract]
Summary of Segment Information	a. Segment revenues and operation results Note 1: Inter-group revenues were eliminated upon consolidation. Note 2: The disaggregated product and service type from the Group's contract with customer is the same as those disclosed in above reportable segment.
Summary of Revenue from Major Products and Services	b. Revenue from major products and services For the Year Ended December 31 2018 2019 2020 NT$ NT$ NT$ US$ (Note 4) Packaging service $ 178,308,222 $ 198,916,897 $ 218,666,071 $ 7,787,253 Testing service 35,903,202 42,658,686 47,271,074 1,683,443 EMS 151,890,384 165,789,479 204,690,669 7,289,554 Others 4,990,613 5,817,122 6,350,896 226,171 $ 371,092,421 $ 413,182,184 $ 476,978,710 $ 16,986,421
Summary of Geographical Information	c. Geographical information 2) Non-current assets December 31 2019 2020 NT$ NT$ US$ (Note 4) Taiwan $ 239,532,971 $ 239,353,978 $ 8,524,002 China 68,747,648 63,907,990 2,275,926 Others 26,645,450 34,107,657 1,214,660 $ 334,926,069 $ 337,369,625 $ 12,014,588 Non-current assets exclude financial instruments, post-employment benefit assets, and deferred tax assets.

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Detail)	Dec. 31, 2020TWD-USDshares	Dec. 31, 2019shares
Disclosure of subsidiaries [line items]
Convenience exchange rate | TWD-USD	28.08
Number of shares in entity held by entity	72,941,000	72,941,000
Bottom of range [member]
Disclosure of subsidiaries [line items]
Number of shares in entity held by entity	1
Percentage of total shares held in Subsidiaries	0.10%

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Summary of Subsidiaries (Detail)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
The Company [Member] | ASE [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the packaging and testing of semiconductors
Establishment and Operating Location	R.O.C.
Percentage of Ownership (%)	100.00%	100.00%
The Company [Member] | USIINC [Member]
Disclosure of subsidiaries [Line Items]
Main Business	Holding company
Establishment and Operating Location	R.O.C.
Percentage of Ownership (%)	100.00%	100.00%
The Company [Member] | SPIL [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the assembly, testing and turnkey services of integrated circuit
Establishment and Operating Location	R.O.C.
Percentage of Ownership (%)	100.00%	100.00%
ASE [Member] | ASE Holding Limited [Member]
Disclosure of subsidiaries [Line Items]
Main Business	Holding company
Establishment and Operating Location	Bermuda
Percentage of Ownership (%)	100.00%	100.00%
ASE [Member] | J & R Holding Limited ("J&R Holding") [member]
Disclosure of subsidiaries [Line Items]
Main Business	Holding company
Establishment and Operating Location	Bermuda
Percentage of Ownership (%)	100.00%	100.00%
ASE [Member] | Innosource Limited [member]
Disclosure of subsidiaries [Line Items]
Main Business	Holding company
Establishment and Operating Location	British Virgin Islands
Percentage of Ownership (%)	100.00%	100.00%
ASE [Member] | Omniquest Industrial Limited [member]
Disclosure of subsidiaries [Line Items]
Main Business	Holding company
Establishment and Operating Location	British Virgin Islands
Percentage of Ownership (%)	71.00%	71.00%
ASE [Member] | ASE Marketing & Service Japan Co., Ltd. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in marketing and sales services
Establishment and Operating Location	Japan
Percentage of Ownership (%)	100.00%	100.00%
ASE [Member] | ASE Test, Inc. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the testing of semiconductors
Establishment and Operating Location	R.O.C.
Percentage of Ownership (%)	100.00%	100.00%
ASE [Member] | Luchu Development Corporation [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the development of real estate properties
Establishment and Operating Location	R.O.C.
Percentage of Ownership (%)	67.10%	67.10%
ASE [Member] | ASEEE [member]
Disclosure of subsidiaries [Line Items]
Main Business	Merged into ASE in February 2020
Establishment and Operating Location	R.O.C.
Percentage of Ownership (%)	0.00%	100.00%
ASE [Member] | Advanced Microelectronic Products Inc. ("AMPI") [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the manufacturing of integrated circuit
Establishment and Operating Location	R.O.C.
Percentage of Ownership (%)	7.60%	7.60%
ASE Test Inc [Member] | Luchu Development Corporation [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the development of real estate properties
Establishment and Operating Location	R.O.C.
Percentage of Ownership (%)	19.00%	19.00%
ASE Test Inc [Member] | TLJ Intertech Inc. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in information software services
Establishment and Operating Location	R.O.C.
Percentage of Ownership (%)	60.00%	60.00%
ASE Test Inc [Member] | MingFeng Information Service Corp., Ltd. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in information software services
Establishment and Operating Location	R.O.C.
Percentage of Ownership (%)	100.00%	100.00%
ASE Test Inc [Member] | Advanced Microelectronic Products Inc. ("AMPI") [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the manufacturing of integrated circuit
Establishment and Operating Location	R.O.C.
Percentage of Ownership (%)	43.40%	43.40%
ASE Test Inc [Member] | Alto Enterprises Limited [member]
Disclosure of subsidiaries [Line Items]
Main Business	Holding company
Establishment and Operating Location	British Virgin Islands
Percentage of Ownership (%)	100.00%	100.00%
ASE Test Inc [Member] | Super Zone Holdings Limited [member]
Disclosure of subsidiaries [Line Items]
Main Business	Holding company
Establishment and Operating Location	Hong Kong
Percentage of Ownership (%)	100.00%	100.00%
ASE Holding Limited [Member] | ASE Test Limited ("ASE Test") [member]
Disclosure of subsidiaries [Line Items]
Main Business	Holding company
Establishment and Operating Location	Singapore
Percentage of Ownership (%)	10.20%	10.20%
ASE Holding Limited [Member] | ASE Investment (Labuan) Inc. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Holding company
Establishment and Operating Location	Malaysia
Percentage of Ownership (%)	70.10%	70.10%
J&R Holding Limited [Member] | Omniquest Industrial Limited [member]
Disclosure of subsidiaries [Line Items]
Main Business	Holding company
Establishment and Operating Location	British Virgin Islands
Percentage of Ownership (%)	8.40%	8.40%
J&R Holding Limited [Member] | ASE Test Limited ("ASE Test") [member]
Disclosure of subsidiaries [Line Items]
Main Business	Holding company
Establishment and Operating Location	Singapore
Percentage of Ownership (%)	89.80%	89.80%
J&R Holding Limited [Member] | J&R Industrial Inc. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in leasing equipment and investing activity
Establishment and Operating Location	R.O.C.
Percentage of Ownership (%)	100.00%	100.00%
J&R Holding Limited [Member] | ASE Japan Co., Ltd. ("ASE Japan") [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the packaging and testing of semiconductors
Establishment and Operating Location	Japan
Percentage of Ownership (%)	100.00%	100.00%
J&R Holding Limited [Member] | ASE (U.S.) Inc. [member]
Disclosure of subsidiaries [Line Items]
Main Business	After-sales service and sales support
Establishment and Operating Location	U.S.A.
Percentage of Ownership (%)	100.00%	100.00%
J&R Holding Limited [Member] | Global Advanced Packaging Technology Limited [member]
Disclosure of subsidiaries [Line Items]
Main Business	Holding company
Establishment and Operating Location	British Cayman Islands
Percentage of Ownership (%)	100.00%	100.00%
J&R Holding Limited [Member] | Suzhou ASEN Semiconductors Co., Ltd. ("ASEN") [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the packaging and testing of semiconductors
Establishment and Operating Location	Suzhou, China
Percentage of Ownership (%)	100.00%	100.00%
J&R Holding Limited [Member] | Anstock Limited [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in financing activity
Establishment and Operating Location	British Cayman Islands
Percentage of Ownership (%)	100.00%	100.00%
J&R Holding Limited [Member] | Anstock II Limited [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in financing activity
Establishment and Operating Location	British Cayman Islands
Percentage of Ownership (%)	100.00%	100.00%
Innosource Limited Investor [Member] | Omniquest Industrial Limited [member]
Disclosure of subsidiaries [Line Items]
Main Business	Holding company
Establishment and Operating Location	British Virgin Islands
Percentage of Ownership (%)	20.60%	20.60%
Innosource Limited Investor [Member] | ASE (Shanghai) Inc. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the production of substrates
Establishment and Operating Location	Shanghai, China
Percentage of Ownership (%)	8.50%	8.50%
Omniquest Industrial Limited [Member] | ASE Corporation [member]
Disclosure of subsidiaries [Line Items]
Main Business	Holding company
Establishment and Operating Location	British Cayman Islands
Percentage of Ownership (%)	100.00%	100.00%
Alto Enterprises Limited [Member] | ASE (Kunshan) Inc. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the packaging and testing of semiconductors
Establishment and Operating Location	Kun Shan, China
Percentage of Ownership (%)	22.90%	22.90%
Alto Enterprises Limited [Member] | ASE Investment (Kun Shan) Limited [member]
Disclosure of subsidiaries [Line Items]
Main Business	Holding company
Establishment and Operating Location	Kun Shan, China
Percentage of Ownership (%)	85.90%	85.90%
Super Zone Holdings Limited [Member] | Advanced Semiconductor Engineering (China) Ltd. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the packaging and testing of semiconductors
Establishment and Operating Location	Shanghai, China
Percentage of Ownership (%)	100.00%	100.00%
ASE Investment Labuan Inc [Member] | ASE (Korea) Inc. ("ASE Korea") [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the packaging and testing of semiconductors
Establishment and Operating Location	Korea
Percentage of Ownership (%)	100.00%	100.00%
ASE Korea [Member] | ASE WeiHai Inc. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the packaging and testing of semiconductors
Establishment and Operating Location	Shandong, China
Percentage of Ownership (%)	100.00%	100.00%
ASE Test [Member] | ASE Test Holdings, Ltd. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Holding company
Establishment and Operating Location	British Cayman Islands
Percentage of Ownership (%)	100.00%	100.00%
ASE Test [Member] | ASE Holdings (Singapore) Pte. Ltd. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Holding company
Establishment and Operating Location	Singapore
Percentage of Ownership (%)	100.00%	100.00%
ASE Test [Member] | ASE Singapore Pte. Ltd. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the packaging and testing of semiconductors
Establishment and Operating Location	Singapore
Percentage of Ownership (%)	100.00%	100.00%
ASE Test [Member] | ASE Investment (Labuan) Inc. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Holding company
Establishment and Operating Location	Malaysia
Percentage of Ownership (%)	29.90%	29.90%
ASE Test Holdings Ltd [Member] | ISE Labs, Inc. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the testing of semiconductors
Establishment and Operating Location	U.S.A.
Percentage of Ownership (%)	100.00%	100.00%
ISE Labs Inc [Member] | ISE Services Inc [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in wafer procurement and customer product management services and commenced operations in February 2020
Establishment and Operating Location	U.S.A.
Percentage of Ownership (%)	100.00%	0.00%
ASE Holdings (Singapore) Pte Ltd [Member] | ASE Electronics (M) Sdn. Bhd. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the packaging and testing of semiconductors
Establishment and Operating Location	Malaysia
Percentage of Ownership (%)	100.00%	100.00%
Global Advanced Packaging Technology Limited [Member] | ASE Assembly & Test (Shanghai) Limited [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the packaging and testing of semiconductors
Establishment and Operating Location	Shanghai, China
Percentage of Ownership (%)	100.00%	100.00%
Global Advanced Packaging Technology Limited [Member] | ASE Advanced Semiconductor Shanghai Limited [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the packaging and testing of semiconductors and was established and spun off from ASESH in November 2020
Establishment and Operating Location	Shanghai, China
Percentage of Ownership (%)	100.00%	0.00%
ASESH [Member] | ASE Investment (Kun Shan) Limited [member]
Disclosure of subsidiaries [Line Items]
Main Business	Holding company
Establishment and Operating Location	Kun Shan, China
Percentage of Ownership (%)	14.10%	14.10%
ASESH [Member] | Shanghai Ding Hui Real Estate Development Co., Ltd. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the development, construction and sale of real estate properties
Establishment and Operating Location	Shanghai, China
Percentage of Ownership (%)	60.00%	60.00%
ASESH [Member] | ISE Labs, China, Ltd. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the testing of semiconductor
Establishment and Operating Location	Shanghai, China
Percentage of Ownership (%)	100.00%	100.00%
ASESH [Member] | Wuxi Tongzhi Microelectronics Co., Ltd. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the packaging and testing of semiconductors
Establishment and Operating Location	Wuxi, China
Percentage of Ownership (%)	100.00%	100.00%
DH [Member] | Shanghai Ding Qi Property Management Co., Ltd. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the management of real estate properties
Establishment and Operating Location	Shanghai, China
Percentage of Ownership (%)	100.00%	100.00%
DH [Member] | Shanghai Ding Wei Real Estate Development Co., Ltd. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the development, construction and leasing of real estate properties
Establishment and Operating Location	Shanghai, China
Percentage of Ownership (%)	100.00%	100.00%
DH [Member] | Shanghai Ding Yu Real Estate Development Co., Ltd. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the development, construction and leasing of real estate properties
Establishment and Operating Location	Shanghai, China
Percentage of Ownership (%)	100.00%	100.00%
DH [Member] | Kun Shan Ding Hong Real Estate Development Co., Ltd. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the development, construction and leasing of real estate properties
Establishment and Operating Location	Kun Shan, China
Percentage of Ownership (%)	100.00%	100.00%
DH [Member] | Shanghai Ding Xu Property Management Co., Ltd. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the management of real estate properties
Establishment and Operating Location	Shanghai, China
Percentage of Ownership (%)	100.00%	100.00%
DH [Member] | Shanghai Dingyao Estate Development Co Ltd [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in property management and was invested in April 2020
Establishment and Operating Location	Shanghai, China
Percentage of Ownership (%)	100.00%	0.00%
DH [Member] | Shanghai Ding Fan Business Management Co Ltd [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the management of real estate properties (acquired from DW in November 2020)
Establishment and Operating Location	Shanghai, China
Percentage of Ownership (%)	100.00%	0.00%
DW [Member] | Shanghai Ding Fan Business Management Co Ltd [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in leasing and management of real estate properties (disposed to DH in November 2020)
Establishment and Operating Location	Shanghai, China
Percentage of Ownership (%)	0.00%	100.00%
ASE Investment Kun Shan Limited [Member] | ASE (Kunshan) Inc. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the packaging and testing of semiconductors
Establishment and Operating Location	Kun Shan, China
Percentage of Ownership (%)	49.30%	49.30%
ASE Corporation [Member] | ASE Mauritius Inc. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Holding company
Establishment and Operating Location	Mauritius
Percentage of Ownership (%)	100.00%	100.00%
ASE Corporation [Member] | ASE Labuan Inc. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Holding company
Establishment and Operating Location	Malaysia
Percentage of Ownership (%)	100.00%	100.00%
ASE Mauritius Inc [Member] | ASE (Kunshan) Inc. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the packaging and testing of semiconductors
Establishment and Operating Location	Kun Shan, China
Percentage of Ownership (%)	27.80%	27.80%
ASE Mauritius Inc [Member] | ASE (Shanghai) Inc. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the production of substrates
Establishment and Operating Location	Shanghai, China
Percentage of Ownership (%)	91.50%	91.50%
ASE Labuan Inc [Member] | ASE Electronics Inc. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the production of substrates
Establishment and Operating Location	R.O.C.
Percentage of Ownership (%)	100.00%	100.00%
ASE (Shanghai) Inc. [Member] | Shanghai Ding Hui Real Estate Development Co., Ltd. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the development, construction and sale of real estate properties
Establishment and Operating Location	Shanghai, China
Percentage of Ownership (%)	40.00%	40.00%
ASE (Shanghai) Inc. [Member] | Advanced Semiconductor Engineering (HK) Limited [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the trading of substrates
Establishment and Operating Location	Hong Kong
Percentage of Ownership (%)	100.00%	100.00%
ASE (Shanghai) Inc. [Member] | Universal Scientific Industrial (Shanghai) Co., Ltd. ("USISH") [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the designing, manufacturing and sales of electronic components
Establishment and Operating Location	Shanghai, China
Percentage of Ownership (%)	0.80%	0.80%
USIINC [Member] | Huntington Holdings International Co., Ltd. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Holding company
Establishment and Operating Location	British Virgin Islands
Percentage of Ownership (%)	100.00%	100.00%
Huntington Holdings International Co Ltd [Member] | Unitech Holdings International Co., Ltd. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Holding company
Establishment and Operating Location	British Virgin Islands
Percentage of Ownership (%)	100.00%	100.00%
Huntington Holdings International Co Ltd [Member] | Real Tech Holdings Limited [member]
Disclosure of subsidiaries [Line Items]
Main Business	Holding company
Establishment and Operating Location	British Virgin Islands
Percentage of Ownership (%)	100.00%	100.00%
Huntington Holdings International Co Ltd [Member] | Universal ABIT Holding Co., Ltd. [member]
Disclosure of subsidiaries [Line Items]
Main Business	In the process of liquidation
Establishment and Operating Location	British Cayman Islands
Percentage of Ownership (%)	100.00%	100.00%
Real Tech Holdings Limited [Member] | Universal Scientific Industrial (Kunshan) Co., Ltd. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Liquidated in June 2020
Establishment and Operating Location	Kun Shan, China
Percentage of Ownership (%)	0.00%	100.00%
Real Tech Holdings Limited [Member] | USI Enterprise Limited ("USIE") [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the service of investment advisory and warehousing management
Establishment and Operating Location	Hong Kong
Percentage of Ownership (%)	95.90%	95.80%
USIE [Member] | USISH [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the designing, manufacturing and sales of electronic components
Establishment and Operating Location	Shanghai, China
Percentage of Ownership (%)	76.60%	77.70%
USISH [Member] | Universal Global Technology Co., Limited [member]
Disclosure of subsidiaries [Line Items]
Main Business	Holding company
Establishment and Operating Location	Hong Kong
Percentage of Ownership (%)	100.00%	100.00%
USISH [Member] | Universal Global Technology (Kunshan) Co., Ltd. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the designing and manufacturing of electronic components
Establishment and Operating Location	Kun Shan, China
Percentage of Ownership (%)	100.00%	100.00%
USISH [Member] | Universal Global Technology (Shanghai) Co., Ltd. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the processing and sales of computer and communication peripherals as well as business in import and export of goods and technology
Establishment and Operating Location	Shanghai, China
Percentage of Ownership (%)	100.00%	100.00%
USISH [Member] | USI Electronics (Shenzhen) Co., Ltd. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the design, manufacturing and sales of motherboards and computer peripherals
Establishment and Operating Location	Shenzhen, China
Percentage of Ownership (%)	50.00%	50.00%
USISH [Member] | Universal Global Electronics (Shanghai) Co., Ltd. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the sales of electronic components and telecommunications equipment
Establishment and Operating Location	Shanghai, China
Percentage of Ownership (%)	100.00%	100.00%
USISH [Member] | Huanrong Electronics (Huizhou) Co., Ltd. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the research and manufacturing of new electronic applications, communications, computers and other electronics products and also provided auxiliary technical services as well as import and export services (acquired from Universal Global Electronics (Shanghai) Co., Ltd. in November 2020)
Establishment and Operating Location	Huizhou, China
Percentage of Ownership (%)	100.00%	0.00%
USISH [Member] | FINANCIERE AFG（FAFG ) [member]
Disclosure of subsidiaries [Line Items]
Main Business	Holding company
Establishment and Operating Location	France
Percentage of Ownership (%)	10.40%	0.00%
Universal Global Technology Co Limited [Member] | USI America Inc. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the manufacturing and processing of motherboards and wireless network communication and provision of related technical service
Establishment and Operating Location	U.S.A.
Percentage of Ownership (%)	100.00%	100.00%
Universal Global Technology Co Limited [Member] | Universal Global Industrial Co., Limited [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in manufacturing, trading and investing activity
Establishment and Operating Location	Hong Kong
Percentage of Ownership (%)	100.00%	100.00%
Universal Global Technology Co Limited [Member] | Universal Global Scientific Industrial Co., Ltd. ("UGTW") [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the manufacturing of components of telecomm and cars and provision of related R&D services
Establishment and Operating Location	R.O.C.
Percentage of Ownership (%)	100.00%	100.00%
Universal Global Technology Co Limited [Member] | Universal Scientific Industrial De Mexico S.A. De C.V. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the assembling of motherboards and computer components
Establishment and Operating Location	Mexico
Percentage of Ownership (%)	100.00%	100.00%
Universal Global Technology Co Limited [Member] | USI Japan Co., Ltd. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the manufacturing and sales of computer peripherals, integrated chip and other related accessories
Establishment and Operating Location	Japan
Percentage of Ownership (%)	100.00%	100.00%
Universal Global Technology Co Limited [Member] | USI Electronics (Shenzhen) Co., Ltd. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the design, manufacturing and sales of motherboards and computer peripherals
Establishment and Operating Location	Shenzhen, China
Percentage of Ownership (%)	50.00%	50.00%
Universal Global Technology Co Limited [Member] | Universal Global Electronics Co., Ltd [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in accepting and outsourcing orders as well as sales of electronic components and service of technical advisory
Establishment and Operating Location	Hong Kong
Percentage of Ownership (%)	100.00%	100.00%
Universal Global Technology Co Limited [Member] | Universal Scientific Industrial (France) ("USIFR") [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in investing activities and was established in August 2019
Establishment and Operating Location	France
Percentage of Ownership (%)	100.00%	100.00%
Universal Global Technology Co Limited [Member] | Universal Scientific Industrial Vietnam Company Limited [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in IC assembly for wearable devices and was established in July 2020.
Establishment and Operating Location	Vietnam
Percentage of Ownership (%)	100.00%	0.00%
UGTW [Member] | Universal Scientific Industrial Co., Ltd. ("USI") [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the manufacturing, processing and sales of computers, computer peripherals and related accessories
Establishment and Operating Location	R.O.C.
Percentage of Ownership (%)	100.00%	100.00%
USI Electronics Shenzhen Co Ltd [Member] | Huanrong Electronics (Huizhou) Co., Ltd. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the research and manufacturing of new electronic applications, communications, computers and other electronics products and also provided auxiliary technical services as well as import and export services (disposed to USISH in November 2020)
Establishment and Operating Location	Huizhou, China
Percentage of Ownership (%)	0.00%	100.00%
Universal Global Electronics Co Ltd [Member] | Semicondutores Avancados do Brasil S.A. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Liquidated in December 2020
Establishment and Operating Location	Brasil
Percentage of Ownership (%)	0.00%	75.00%
Universal Global Electronics Co Ltd [Member] | Universal Scientific Industrial Poland Sp. z o.o. ("USIPL") (The name was changed on June 2020 and the former name was Chung Hong Electronics Poland Sp. z o.o.)
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the design and manufacturing of electronic components and new electronic applications
Establishment and Operating Location	Poland
Percentage of Ownership (%)	100.00%	60.00%
Universal Global Electronics (Shanghai) Co., Ltd. [member] | USI Science and Technology (Shenzhen) Co., Ltd. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the design of electronic components, service of technical advisory; wholesale of electronic components and communication peripherals as well as business in import and export of goods and management of properties and was established in November 2020.
Establishment and Operating Location	Shenzhen, China
Percentage of Ownership (%)	100.00%	0.00%
USIFR [Member] | FAFG [member]
Disclosure of subsidiaries [Line Items]
Main Business	Holding company
Establishment and Operating Location	France
Percentage of Ownership (%)	89.60%	0.00%
USIFR [Member] | ASTEELFLASH GROUP [Member]
Disclosure of subsidiaries [Line Items]
Main Business	Holding company
Establishment and Operating Location	France
Percentage of Ownership (%)		0.00%
FAFG [member] | ASTEELFLASH GROUP [Member]
Disclosure of subsidiaries [Line Items]
Main Business	Holding company
Establishment and Operating Location	France
Percentage of Ownership (%)	100.00%	0.00%
FAFG [member] | MANUFACTURING POWER TUNISIA [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the design and manufacturing of electronic components
Establishment and Operating Location	Tunisia
Percentage of Ownership (%)	0.10%
FAFG [member] | ASTEELFLASH MEXICO S.A. de C.V. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the design and manufacturing of electronic components
Establishment and Operating Location	Mexico
Percentage of Ownership (%)	0.10%
ASTEELFLASH GROUP [member] | MANUFACTURING POWER TUNISIA [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the design and manufacturing of electronic components
Establishment and Operating Location	Tunisia
Percentage of Ownership (%)	99.90%	0.00%
ASTEELFLASH GROUP [member] | ASTEELFLASH MEXICO S.A. de C.V. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the design and manufacturing of electronic components
Establishment and Operating Location	Mexico
Percentage of Ownership (%)	99.90%	0.00%
ASTEELFLASH GROUP [member] | ASTEELFLASH (BEDFORD) LIMITED [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the design and manufacturing of electronic components
Establishment and Operating Location	United Kingdom
Percentage of Ownership (%)	100.00%	0.00%
ASTEELFLASH GROUP [member] | ASTEELFLASH FRANCE [Member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the design and manufacturing of electronic components
Establishment and Operating Location	France
Percentage of Ownership (%)	99.90%	0.00%
ASTEELFLASH GROUP [member] | ASTEELFLASH TUNISIE S.A. [Member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the design and manufacturing of electronic components
Establishment and Operating Location	Tunisia
Percentage of Ownership (%)	100.00%	0.00%
ASTEELFLASH GROUP [member] | ASTEELFLASH HONG KONG LIMITED [Member]
Disclosure of subsidiaries [Line Items]
Main Business	Holding company
Establishment and Operating Location	Hong Kong
Percentage of Ownership (%)	100.00%	0.00%
ASTEELFLASH GROUP [member] | ASTEELFLASH GERMANY GmbH [Member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the design and manufacturing of electronic components
Establishment and Operating Location	Germany
Percentage of Ownership (%)	100.00%	0.00%
ASTEELFLASH GROUP [member] | ASTEELFLASH US HOLDING CORP [Member]
Disclosure of subsidiaries [Line Items]
Main Business	Holding company
Establishment and Operating Location	U.S.A.
Percentage of Ownership (%)	100.00%	0.00%
ASTEELFLASH GROUP [member] | ASTEEL ELECTRONIQUE FOUCHANA [Member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the design and manufacturing of electronic components
Establishment and Operating Location	Tunisia
Percentage of Ownership (%)		0.00%
ASTEELFLASH GROUP [member] | AFERH TUNISIE [Member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the management, training and consulting of human resources
Establishment and Operating Location	Tunisia
Percentage of Ownership (%)	0.50%	0.00%
ASTEELFLASH GROUP [member] | ASTEEL ELECTRONICS MANUFACTURING SERVICES [Member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the design and manufacturing of electronic components
Establishment and Operating Location	Tunisia
Percentage of Ownership (%)	0.10%
ASTEELFLASH (BEDFORD) LIMITED [Member] | ASTEELFLASH TUNISIE S.A. [Member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the design and manufacturing of electronic components
Establishment and Operating Location	Tunisia
Percentage of Ownership (%)		0.00%
ASTEELFLASH TECHNOLOGIE [Member] | ASTEELFLASH FRANCE [Member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the design and manufacturing of electronic components
Establishment and Operating Location	France
Percentage of Ownership (%)		0.00%
ASTEELFLASH FRANCE [Member] | ASTEELFLASH TUNISIE S.A. [Member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the design and manufacturing of electronic components
Establishment and Operating Location	Tunisia
Percentage of Ownership (%)		0.00%
ASTEELFLASH FRANCE [Member] | ASTEEL ELECTRONIQUE FOUCHANA [Member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the design and manufacturing of electronic components
Establishment and Operating Location	Tunisia
Percentage of Ownership (%)	94.20%	0.00%
ASTEELFLASH FRANCE [Member] | ASTEEL ELECTRONICS MANUFACTURING SERVICES [Member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the design and manufacturing of electronic components
Establishment and Operating Location	Tunisia
Percentage of Ownership (%)	99.90%	0.00%
ASTEELFLASH FRANCE [Member] | SCI CHASSET [Member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the management and operation of real estate properties and holding the ownership of real estate properties
Establishment and Operating Location	France
Percentage of Ownership (%)	100.00%	0.00%
ASTEELFLASH FRANCE [Member] | AFERH [Member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the management, training and consulting of human resources
Establishment and Operating Location	France
Percentage of Ownership (%)	100.00%	0.00%
ASTEELFLASH FRANCE [Member] | ASTEELFLASH TECHNOLOGIE [Member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in projection of plastic and the design and manufacturing of industrial components
Establishment and Operating Location	France
Percentage of Ownership (%)	100.00%	0.00%
ASTEELFLASH FRANCE [Member] | ASTEELFLASH BRETAGNE [Member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the design and manufacturing of electronic components
Establishment and Operating Location	France
Percentage of Ownership (%)	100.00%	0.00%
ASTEELFLASH TUNISIE S.A. [member] | ASTEEL ELECTRONIQUE TUNISIE [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the design and manufacturing of electronic components
Establishment and Operating Location	Tunisia
Percentage of Ownership (%)	100.00%	0.00%
ASTEELFLASH TUNISIE S.A. [member] | ASTEEL ELECTRONIQUE FOUCHANA [Member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the design and manufacturing of electronic components
Establishment and Operating Location	Tunisia
Percentage of Ownership (%)		0.00%
AFERH [Member] | AFERH TUNISIE [Member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the management, training and consulting of human resources
Establishment and Operating Location	Tunisia
Percentage of Ownership (%)	99.50%	0.00%
ASTEELFLASH HONG KONG LIMITED [Member] | ASTEELFLASH SUZHOU CO LTD [Member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the design and manufacturing of electronic components
Establishment and Operating Location	Suzhou, China
Percentage of Ownership (%)	100.00%	0.00%
ASTEELFLASH SUZHOU CO., LTD. [member] | ASTEELFLASH TUNISIE S.A. [Member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the design and manufacturing of electronic components
Establishment and Operating Location	Tunisia
Percentage of Ownership (%)		0.00%
ASTEELFLASH SUZHOU CO., LTD. [member] | ASTEEL ELECTRONIQUE FOUCHANA [Member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the design and manufacturing of electronic components
Establishment and Operating Location	Tunisia
Percentage of Ownership (%)		0.00%
ASTEELFLASH GERMANY GmbH [member] | ASTEELFLASH TUNISIE S.A. [Member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the design and manufacturing of electronic components
Establishment and Operating Location	Tunisia
Percentage of Ownership (%)		0.00%
ASTEELFLASH GERMANY GmbH [member] | ASTEELFLASH HERSFELD GmbH [Member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the design and manufacturing of electronic components
Establishment and Operating Location	Germany
Percentage of Ownership (%)	100.00%	0.00%
ASTEELFLASH GERMANY GmbH [member] | ASTEELFLASH EBERBACH GmbH [Member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the design and manufacturing of electronic components
Establishment and Operating Location	Germany
Percentage of Ownership (%)	100.00%	0.00%
ASTEELFLASH GERMANY GmbH [member] | ASTEELFLASH BONN GmbH [Member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the design and manufacturing of electronic components
Establishment and Operating Location	Germany
Percentage of Ownership (%)	100.00%	0.00%
ASTEELFLASH GERMANY GmbH [member] | ASTEELFLASH SCHWANDORF GmbH [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the design and manufacturing of electronic components
Establishment and Operating Location	Germany
Percentage of Ownership (%)	100.00%	0.00%
ASTEELFLASH GERMANY GmbH [member] | ASTEELFLASH PLZEN S.R.O. [Member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the design and manufacturing of electronic components
Establishment and Operating Location	Czech Republic
Percentage of Ownership (%)	100.00%	0.00%
ASTEELFLASH GERMANY GmbH [member] | ASTEELFLASH DESIGN SOLUTIONS HAMBOURG GmbH [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the design and manufacturing of electronic components
Establishment and Operating Location	Germany
Percentage of Ownership (%)	100.00%	0.00%
ASTEELFLASH GERMANY GmbH [member] | EN ELECTRONICNETWORK SRL [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the design and manufacturing of electronic components
Establishment and Operating Location	Romania
Percentage of Ownership (%)	100.00%	0.00%
ASTEELFLASH MEXICO S.A. de C.V. [member] | ASTEELFLASH TUNISIE S.A. [Member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the design and manufacturing of electronic components
Establishment and Operating Location	Tunisia
Percentage of Ownership (%)		0.00%
ASTEELFLASH US HOLDING CORP. [member] | ASTEELFLASH USA CORP [Member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the design and manufacturing of electronic components
Establishment and Operating Location	U.S.A.
Percentage of Ownership (%)	100.00%	0.00%
ASTEELFLASH USA CORP. [member] | ASTEELFLASH TUNISIE S.A. [Member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the design and manufacturing of electronic components
Establishment and Operating Location	Tunisia
Percentage of Ownership (%)		0.00%
ASTEELFLASH USA CORP. [member] | ASTEEL ELECTRONIQUE FOUCHANA [Member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the design and manufacturing of electronic components
Establishment and Operating Location	Tunisia
Percentage of Ownership (%)		0.00%
SPIL [Member] | SPIL (B.V.I.) Holding Limited [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in investing activities
Establishment and Operating Location	British Virgin Islands
Percentage of Ownership (%)	100.00%	100.00%
SPIL [Member] | Siliconware Investment Co., Ltd. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in investing activities
Establishment and Operating Location	R.O.C.
Percentage of Ownership (%)	100.00%	100.00%
SPIL (B.V.I.) Holding Limited [Member] | Siliconware USA, Inc. [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in marketing activities
Establishment and Operating Location	U.S.A.
Percentage of Ownership (%)	100.00%	100.00%
SPIL (B.V.I.) Holding Limited [Member] | SPIL (Cayman) Holding Limited [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in investing activities
Establishment and Operating Location	British Cayman Islands
Percentage of Ownership (%)	100.00%	100.00%
SPIL Cayman Holding Limited [Member] | Siliconware Technology (Suzhou) Limited ("SZ") [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the packaging and testing of semiconductors
Establishment and Operating Location	Suzhou, China
Percentage of Ownership (%)	100.00%	100.00%
SPIL Cayman Holding Limited [Member] | Siliconware Electronics (Fujian) Co., Limited ("SF") [member]
Disclosure of subsidiaries [Line Items]
Main Business	Engaged in the packaging and testing of semiconductors and was disposed in October 2020 (Note 30)
Establishment and Operating Location	Fujian, China
Percentage of Ownership (%)	0.00%	100.00%

Cash and Cash Equivalents - Sum

Cash and Cash Equivalents - Summary of Cash and Cash Equivalents (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018TWD ($)	Dec. 31, 2017TWD ($)
Cash and cash equivalents [abstract]
Cash on hand	$ 6,073	$ 216	$ 6,567
Checking accounts and demand deposits	48,734,866	1,735,572	44,565,936
Cash equivalents Cash equivalents (time deposits with original maturity of less than three months)	2,797,132	99,613	15,558,372
Cash and cash equivalents,total	$ 51,538,071	$ 1,835,401	$ 60,130,875	$ 2,141,413	$ 51,518,436	$ 46,078,066

Financial Instruments at Fair_3

Financial Instruments at Fair Value Through Profit or Loss - Summary of Financial Instruments at Fair Value Through Profit or Loss (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Disclosure of detailed information about financial instruments [line items]
Financial assets mandatorily classified as at FVTPL	$ 6,135,793	$ 218,511	$ 5,288,996
Current	4,342,605	154,651	4,127,566
Non-current	1,793,188	63,860	1,161,430
Financial liabilities held for trading	1,537,208	54,744	973,571
Quoted ordinary shares [member] | Non derivative financial assets [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets mandatorily classified as at FVTPL	4,064,438	144,745	3,460,123
Open-end mutual funds [member] | Non derivative financial assets [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets mandatorily classified as at FVTPL	339,338	12,085	662,290
Forward Exchange Contract [member] | Derivative financial instruments [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets mandatorily classified as at FVTPL	122,511	4,363	104,308
Financial liabilities held for trading	9,020	321	110,990
Swap contracts [member] | Derivative financial instruments [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets mandatorily classified as at FVTPL	99,312	3,537	56,561
Financial liabilities held for trading	1,448,972	51,602	862,581
Call option [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets mandatorily classified as at FVTPL			24,556
Call option [member] | Derivative financial instruments [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets mandatorily classified as at FVTPL			24,556
Unquoted preferred shares [member] | Non derivative financial assets [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets mandatorily classified as at FVTPL	385,440	13,726	377,440
Private-placement funds [member] | Non derivative financial assets [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets mandatorily classified as at FVTPL	1,124,754	40,055	$ 603,718
Target redemption forward contracts [Member] | Derivative financial instruments [member]
Disclosure of detailed information about financial instruments [line items]
Financial liabilities held for trading	$ 79,216	$ 2,821

Financial Instruments at Fair_4

Financial Instruments at Fair Value Through Profit or Loss - Summary of Outstanding Contracts Not Accounted for Hedge Accounting (Detail) € in Thousands, ₩ in Thousands, ¥ in Thousands, ¥ in Thousands, RM in Thousands, $ in Thousands, $ in Thousands, $ in Thousands, $ in Thousands

12 Months Ended

Dec. 31, 2020TWD ($)

Dec. 31, 2019TWD ($)

Dec. 31, 2020USD ($)

Dec. 31, 2020CNY (¥)

Dec. 31, 2020HKD ($)

Dec. 31, 2020JPY (¥)

Dec. 31, 2020EUR (€)

Dec. 31, 2020KRW (₩)

Dec. 31, 2020MYR (RM)

Dec. 31, 2020SGD ($)

Dec. 31, 2019USD ($)

Dec. 31, 2019CNY (¥)

Dec. 31, 2019HKD ($)

Dec. 31, 2019JPY (¥)

Dec. 31, 2019KRW (₩)

Dec. 31, 2019MYR (RM)

Dec. 31, 2019SGD ($)

Disclosure of detailed information about financial instruments [line items]

Maturity Period

2020-01

Sell NT$/buy US$ [member] | Bottom of range [member]

Disclosure of detailed information about financial instruments [line items]

Maturity Period

2020-01

Sell NT$/buy US$ [member] | Top of range [member]

Disclosure of detailed information about financial instruments [line items]

Maturity Period

2021-12

2020-12

Sell US$/Buy RMB [member]

Disclosure of detailed information about financial instruments [line items]

Maturity Period

2020-02

Sell US$/Buy RMB [member] | Bottom of range [member]

Disclosure of detailed information about financial instruments [line items]

Maturity Period

2021-01

Sell US$/Buy RMB [member] | Top of range [member]

Disclosure of detailed information about financial instruments [line items]

Maturity Period

2021-02

Sell US$/buy JPY [member] | Bottom of range [member]

Disclosure of detailed information about financial instruments [line items]

Maturity Period

2020-02

Sell US$/buy JPY [member] | Top of range [member]

Disclosure of detailed information about financial instruments [line items]

Maturity Period

2020-03

Sell US$/buy NT$ [member]

Disclosure of detailed information about financial instruments [line items]

Maturity Period

2020-01

Sell US$/buy NT$ [member] | Bottom of range [member]

Disclosure of detailed information about financial instruments [line items]

Maturity Period

2021-01

Sell US$/Buy KRW [member]

Disclosure of detailed information about financial instruments [line items]

Maturity Period

2021-01

2020-01

Sell US$/Buy MYR [member]

Disclosure of detailed information about financial instruments [line items]

Maturity Period

2021-01

2020-01

Sell US/Buy HKD$ [member]

Disclosure of detailed information about financial instruments [line items]

Maturity Period

2021-02

Swap contracts [member] | Sell NT$/buy US$ [member]

Disclosure of detailed information about financial instruments [line items]

Notional Amount

$ 51,140,082

$ 50,241,799

$ 1,755,000

$ 1,660,000

Swap contracts [member] | Sell NT$/buy US$ [member] | Bottom of range [member]

Disclosure of detailed information about financial instruments [line items]

Maturity Period

2021-01

Swap contracts [member] | Sell US$/Buy RMB [member]

Disclosure of detailed information about financial instruments [line items]

Notional Amount

59,793

¥ 395,742

49,666

¥ 349,800

Swap contracts [member] | Sell US$/buy JPY [member]

Disclosure of detailed information about financial instruments [line items]

Notional Amount

41,630

¥ 4,300,000

45,878

¥ 5,000,000

Swap contracts [member] | Sell US$/buy NT$ [member]

Disclosure of detailed information about financial instruments [line items]

Notional Amount

$ 19,073,846

$ 5,719,478

675,240

189,960

Swap contracts [member] | Sell US$/buy NT$ [member] | Top of range [member]

Disclosure of detailed information about financial instruments [line items]

Maturity Period

2021-02

Swap contracts [member] | Sell US$/Buy KRW [member]

Disclosure of detailed information about financial instruments [line items]

Notional Amount

30,000

₩ 33,066,000

28,000

₩ 32,454,800

Swap contracts [member] | Sell US$/Buy MYR [member]

Disclosure of detailed information about financial instruments [line items]

Notional Amount

11,000

RM 45,507

Swap contracts [member] | Sell US/Buy HKD$ [member]

Disclosure of detailed information about financial instruments [line items]

Notional Amount

13,804

$ 107,000

Forward exchange contracts [member]

Disclosure of detailed information about financial instruments [line items]

Maturity Period

2020-01

Forward exchange contracts [member] | Sell RMB/Buy US$ [member]

Disclosure of detailed information about financial instruments [line items]

Maturity Period

2021-01

Notional Amount

116,093

756,946

316,896

2,224,491

Forward exchange contracts [member] | Sell RMB/Buy US$ [member] | Top of range [member]

Disclosure of detailed information about financial instruments [line items]

Maturity Period

2020-02

Forward exchange contracts [member] | Sell NT$/buy US$ [member]

Disclosure of detailed information about financial instruments [line items]

Maturity Period

2020-01

Notional Amount

$ 2,667,230

$ 2,275,860

95,000

75,000

Forward exchange contracts [member] | Sell NT$/buy US$ [member] | Bottom of range [member]

Disclosure of detailed information about financial instruments [line items]

Maturity Period

2021-01

Forward exchange contracts [member] | Sell NT$/buy US$ [member] | Top of range [member]

Disclosure of detailed information about financial instruments [line items]

Maturity Period

2021-02

Forward exchange contracts [member] | Sell US$/Buy RMB [member]

Disclosure of detailed information about financial instruments [line items]

Notional Amount

363,000

¥ 2,385,500

109,000

¥ 767,277

Forward exchange contracts [member] | Sell US$/Buy RMB [member] | Bottom of range [member]

Disclosure of detailed information about financial instruments [line items]

Maturity Period

2021-01

2020-01

Forward exchange contracts [member] | Sell US$/Buy RMB [member] | Top of range [member]

Disclosure of detailed information about financial instruments [line items]

Maturity Period

2021-04

2020-03

Forward exchange contracts [member] | Sell US$/buy JPY [member]

Disclosure of detailed information about financial instruments [line items]

Notional Amount

100,076

¥ 10,405,845

87,398

¥ 9,509,491

Forward exchange contracts [member] | Sell US$/buy NT$ [member]

Disclosure of detailed information about financial instruments [line items]

Notional Amount

$ 776,867

$ 5,142,441

27,470

170,000

Forward exchange contracts [member] | Sell US$/buy NT$ [member] | Bottom of range [member]

Disclosure of detailed information about financial instruments [line items]

Maturity Period

2021-01

2020-01

Forward exchange contracts [member] | Sell US$/buy NT$ [member] | Top of range [member]

Disclosure of detailed information about financial instruments [line items]

Maturity Period

2021-02

2020-02

Forward exchange contracts [member] | Sell HKD/Buy US$ [member]

Disclosure of detailed information about financial instruments [line items]

Maturity Period

2021-01

2020-01

Notional Amount

529

$ 4,100

218,297

$ 1,705,281

Forward exchange contracts [member] | Sell US$/Buy EUR [member]

Disclosure of detailed information about financial instruments [line items]

Maturity Period

2021-01

Notional Amount

1,607

€ 1,320

Forward exchange contracts [member] | Sell US$/Buy KRW [member]

Disclosure of detailed information about financial instruments [line items]

Notional Amount

16,000

₩ 17,575,300

Forward exchange contracts [member] | Sell US$/Buy MYR [member]

Disclosure of detailed information about financial instruments [line items]

Notional Amount

24,000

RM 98,737

26,000

RM 108,330

Forward exchange contracts [member] | Sell US$/Buy MYR [member] | Bottom of range [member]

Disclosure of detailed information about financial instruments [line items]

Maturity Period

2021-01

2020-01

Forward exchange contracts [member] | Sell US$/Buy MYR [member] | Top of range [member]

Disclosure of detailed information about financial instruments [line items]

Maturity Period

2021-04

2020-05

Forward exchange contracts [member] | Sell US$/Buy SGD [member]

Disclosure of detailed information about financial instruments [line items]

Notional Amount

18,500

$ 24,868

$ 8,600

$ 11,691

Forward exchange contracts [member] | Sell US$/Buy SGD [member] | Bottom of range [member]

Disclosure of detailed information about financial instruments [line items]

Maturity Period

2021-01

Forward exchange contracts [member] | Sell US$/Buy SGD [member] | Top of range [member]

Disclosure of detailed information about financial instruments [line items]

Maturity Period

2020-02

Target redemption forward contracts [member] | Sell EUR/Buy US$ [member]

Disclosure of detailed information about financial instruments [line items]

Notional Amount

$ 27,475

€ 23,279

Target redemption forward contracts [member] | Sell EUR/Buy US$ [member] | Bottom of range [member]

Disclosure of detailed information about financial instruments [line items]

Maturity Period

2022-04

Target redemption forward contracts [member] | Sell EUR/Buy US$ [member] | Top of range [member]

Disclosure of detailed information about financial instruments [line items]

Maturity Period

2022-06

Financial Assets at Fair Valu_3

Financial Assets at Fair Value Through Other Comprehensive Income - Summary of Financial Assets at Fair Value Through Other Comprehensive Income (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Financial assets at fair value through other comprehensive income [abstract]
Investments in equity instruments at FVTOCI	$ 728,398	$ 25,940	$ 755,903
Investments in debt instruments at FVTOCI	1,012,736	36,066	1,014,872
Total	$ 1,741,134	$ 62,006	$ 1,770,775

Financial Assets at Fair Valu_4

Financial Assets at Fair Value Through Other Comprehensive Income - Summary of Investments in Equity Instruments at Fair Value Through Other Comprehensive Income (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Disclosure of fair value of investments in equity instruments designated at fair value through other comprehensive income [line items]
Investments in equity instruments at FVTOCI	$ 728,398	$ 25,940	$ 755,903
Unquoted ordinary shares [member]
Disclosure of fair value of investments in equity instruments designated at fair value through other comprehensive income [line items]
Investments in equity instruments at FVTOCI	567,377	20,206	565,028
Limited partnership [member]
Disclosure of fair value of investments in equity instruments designated at fair value through other comprehensive income [line items]
Investments in equity instruments at FVTOCI	9,692	345	32,157
Unquoted preferred shares [member]
Disclosure of fair value of investments in equity instruments designated at fair value through other comprehensive income [line items]
Investments in equity instruments at FVTOCI	$ 151,329	$ 5,389	$ 158,718

Financial Assets at Fair Valu_5

Financial Assets at Fair Value Through Other Comprehensive Income - Summary of Investments in Debt Instruments at Fair Value Through Other Comprehensive Income (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Financial assets at fair value through other comprehensive income [line items]
Investments in debt instruments at FVTOCI	$ 1,012,736	$ 36,066	$ 1,014,872
Unsecured subordinate corporate bonds [member]
Financial assets at fair value through other comprehensive income [line items]
Investments in debt instruments at FVTOCI	$ 1,012,736	$ 36,066	$ 1,014,872

Financial Assets at Fair Valu_6

Financial Assets at Fair Value Through Other Comprehensive Income - Additional Information (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)Bonds	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2019USD ($)
Financial assets at fair value through other comprehensive income [line items]
Unsecured subordinate corporate bonds amount	$ 1,082,000	$ 38,533	$ 1,325,327
Unsecured subordinate corporate bonds [member]
Financial assets at fair value through other comprehensive income [line items]
Unsecured subordinate corporate bonds amount	$ 1,000,000	$ 36	$ 1,000	$ 36
Number of bonds acquired	1,000
Corporate bonds annual interest rate	3.50%	3.50%	3.50%	3.50%
Effective interest rate	3.20%	3.20%	3.20%	3.20%

Trade Receivables, Net - Summar

Trade Receivables, Net - Summary of Trade Receivables, Net (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Disclosure of financial assets [Line Items]
Trade receivables	$ 91,207,576	$ 3,248,133	$ 76,918,783
At FVTOCI	626,413	22,308	2,029,690
Total trade receivable	91,833,989	3,270,441	78,948,473
Cost [member]
Disclosure of financial assets [Line Items]
Trade receivables	91,304,934	3,251,600	77,055,280
Allowance for doubtful debts [member]
Disclosure of financial assets [Line Items]
Trade receivables	$ 97,358	$ 3,467	$ 136,497

Trade Receivables, Net - Additi

Trade Receivables, Net - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2020
Bottom of range [member]
Disclosure of financial assets [Line Items]
Average credit terms	30 days
Top of range [member]
Disclosure of financial assets [Line Items]
Average credit terms	90 days

Trade Receivables, Net - Summ_2

Trade Receivables, Net - Summary of Loss Allowance of Trade Receivables Based on Group's Provision Matrix (Detail) - Trade receivables [member] $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Disclosure of provision matrix [line items]
Gross carrying amount	$ 91,304,934	$ 3,251,600	$ 77,055,280
Loss allowance (Lifetime ECL)	(97,358)	(3,467)	(136,497)
Net Amount	$ 91,207,576	$ 3,248,133	$ 76,918,783
Top of range [member]
Disclosure of provision matrix [line items]
Expected credit loss rate	10.00%	10.00%
Not past due [member]
Disclosure of provision matrix [line items]
Expected credit loss rate	0.00%	0.00%	0.00%
Gross carrying amount	$ 86,820,792	$ 3,091,908	$ 70,042,018
Loss allowance (Lifetime ECL)	(18,911)	(673)	(12,379)
Net Amount	86,801,881	3,091,235	70,029,639
Less than 1 month [member]
Disclosure of provision matrix [line items]
Gross carrying amount	3,823,249	136,156	6,111,309
Loss allowance (Lifetime ECL)	(2,053)	(73)	(841)
Net Amount	$ 3,821,196	$ 136,083	$ 6,110,468
Less than 1 month [member] | Bottom of range [member]
Disclosure of provision matrix [line items]
Expected credit loss rate	0.00%	0.00%	0.00%
Less than 1 month [member] | Top of range [member]
Disclosure of provision matrix [line items]
Expected credit loss rate	10.00%	10.00%	10.00%
1 to 3 months [member]
Disclosure of provision matrix [line items]
Gross carrying amount	$ 557,487	$ 19,854	$ 695,384
Loss allowance (Lifetime ECL)	(20,629)	(735)	(26,587)
Net Amount	$ 536,858	$ 19,119	$ 668,797
1 to 3 months [member] | Bottom of range [member]
Disclosure of provision matrix [line items]
Expected credit loss rate	0.00%	0.00%	0.00%
1 to 3 months [member] | Top of range [member]
Disclosure of provision matrix [line items]
Expected credit loss rate	70.00%	70.00%	70.00%
More than 91 days [member]
Disclosure of provision matrix [line items]
Gross carrying amount	$ 92,873	$ 3,307	$ 153,458
Loss allowance (Lifetime ECL)	(45,232)	(1,611)	(53,629)
Net Amount	$ 47,641	$ 1,696	$ 99,829
More than 91 days [member] | Bottom of range [member]
Disclosure of provision matrix [line items]
Expected credit loss rate	1.00%	1.00%	1.00%
More than 91 days [member] | Top of range [member]
Disclosure of provision matrix [line items]
Expected credit loss rate	100.00%	100.00%	100.00%
Individually impaired [member]
Disclosure of provision matrix [line items]
Gross carrying amount	$ 10,533	$ 375	$ 53,111
Loss allowance (Lifetime ECL)	$ (10,533)	$ (375)	(43,061)
Net Amount			$ 10,050
Individually impaired [member] | Bottom of range [member]
Disclosure of provision matrix [line items]
Expected credit loss rate	50.00%	50.00%	50.00%
Individually impaired [member] | Top of range [member]
Disclosure of provision matrix [line items]
Expected credit loss rate	100.00%	100.00%	100.00%

Trade Receivables, Net - Summ_3

Trade Receivables, Net - Summary of Movements of Loss Allowance of Trade Receivables (Detail) - Trade receivables [member] $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Disclosure of financial assets [Line Items]
Beginning balance	$ 136,497	$ 4,861	$ 155,389	$ 64,901
Net remeasurement of loss allowance	(55,742)	(1,985)	(38,277)	150,128
Reclassification	(6,970)	(248)	(5,877)
Acquisition through business combinations	32,460	1,156	25,553	3,482
Amounts written off	(3,944)	(141)		(60,109)
Effects of foreign currency exchange differences	(4,943)	(176)	(291)	(3,013)
Ending balance	$ 97,358	$ 3,467	$ 136,497	$ 155,389

Trade Receivables, Net - Summ_4

Trade Receivables, Net - Summary of Loss Allowance For Current Financial Assets At FVTOCI (Details) - Trade receivables [member] $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Disclosure For Loss Allowance For Current Financial Assets At FVTOCI [Line Items]
Gross carrying amount	$ 626,413	$ 22,308	$ 2,029,691
Loss allowance (Lifetime ECLs)			(1)
Net Amount	$ 626,413	$ 22,308	$ 2,029,690
Not past due [member]
Disclosure For Loss Allowance For Current Financial Assets At FVTOCI [Line Items]
Expected credit loss rate	0.00%	0.00%	0.00%
Gross carrying amount	$ 613,968	$ 21,864	$ 2,029,324
Net Amount	$ 613,968	$ 21,864	$ 2,029,324
Less than 1 month [member]
Disclosure For Loss Allowance For Current Financial Assets At FVTOCI [Line Items]
Expected credit loss rate	0.00%	0.00%
Gross carrying amount	$ 9,874	$ 352
Net Amount	$ 9,874	$ 352
1 to 3 months [member]
Disclosure For Loss Allowance For Current Financial Assets At FVTOCI [Line Items]
Expected credit loss rate	0.00%	0.00%	0.00%
Gross carrying amount	$ 2,571	$ 92	$ 207
Net Amount	$ 2,571	$ 92	$ 207
More than 91 days [member]
Disclosure For Loss Allowance For Current Financial Assets At FVTOCI [Line Items]
Expected credit loss rate			1.00%
Gross carrying amount			$ 160
Loss allowance (Lifetime ECLs)			(1)
Net Amount			$ 159

Trade Receivables, Net - Trans

Trade Receivables, Net - Transfer of Financial Asset (Detail) € in Thousands, $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2020EUR (€)	Dec. 31, 2019TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2020EUR (€)
Receivables Factoring Proceeds [Member] | BNP Paribas [Member]
Disclosure of transferred financial assets that are not derecognised in their entirety [line items]
Assets that entity continues to recognise						€ 16,691
Receivables Factoring Proceeds [Member] | HSBC [Member]
Disclosure of transferred financial assets that are not derecognised in their entirety [line items]
Assets that entity continues to recognise						6,773
Receivables Factoring Proceeds [Member] | Citi Bank Taiwan Limited [Member]
Disclosure of transferred financial assets that are not derecognised in their entirety [line items]
Assets that entity continues to recognise | $					$ 94,471
Receivables Factoring Proceeds [Member] | Standard Chartered Bank [Member]
Disclosure of transferred financial assets that are not derecognised in their entirety [line items]
Assets that entity continues to recognise | $					$ 53,800
Receivables Factoring Proceeds [Member] | First Commercial Bank [Member]
Disclosure of transferred financial assets that are not derecognised in their entirety [line items]
Assets that entity continues to recognise | $	$ 6,879			$ 7,567
Reclassified to Other Receivables [Member] | BNP Paribas [Member]
Disclosure of transferred financial assets that are not derecognised in their entirety [line items]
Transferred to other receivables						15,315
Reclassified to Other Receivables [Member] | HSBC [Member]
Disclosure of transferred financial assets that are not derecognised in their entirety [line items]
Transferred to other receivables						€ 6,456
Advances Received But Unused [Member] | BNP Paribas [Member]
Disclosure of transferred financial assets that are not derecognised in their entirety [line items]
Advances received			€ 14,481
Advances Received But Unused [Member] | HSBC [Member]
Disclosure of transferred financial assets that are not derecognised in their entirety [line items]
Advances received			5,779
Advances Received Used [Member] | BNP Paribas [Member]
Disclosure of transferred financial assets that are not derecognised in their entirety [line items]
Advances received			1,376
Advances Received Used [Member] | HSBC [Member]
Disclosure of transferred financial assets that are not derecognised in their entirety [line items]
Advances received			€ 317
Advances Received Used [Member] | Citi Bank Taiwan Limited [Member]
Disclosure of transferred financial assets that are not derecognised in their entirety [line items]
Advances received | $		$ 94,471
Advances Received Used [Member] | Standard Chartered Bank [Member]
Disclosure of transferred financial assets that are not derecognised in their entirety [line items]
Advances received | $		$ 53,800
Advances Received Used [Member] | First Commercial Bank [Member]
Disclosure of transferred financial assets that are not derecognised in their entirety [line items]
Advances received | $	$ 6,879			$ 7,567
Interest Rate On Advances Received Against Trade Receivables Sold [Member] | BNP Paribas [Member]
Disclosure of transferred financial assets that are not derecognised in their entirety [line items]
Interest rates on advances received	0.80%	0.80%	0.80%
Interest Rate On Advances Received Against Trade Receivables Sold [Member] | HSBC [Member]
Disclosure of transferred financial assets that are not derecognised in their entirety [line items]
Interest rates on advances received	1.45%	1.45%	1.45%
Interest Rate On Advances Received Against Trade Receivables Sold [Member] | Citi Bank Taiwan Limited [Member] | Maximum [Member]
Disclosure of transferred financial assets that are not derecognised in their entirety [line items]
Interest rates on advances received	0.95%	0.95%	0.95%
Interest Rate On Advances Received Against Trade Receivables Sold [Member] | Citi Bank Taiwan Limited [Member] | Minimum [Member]
Disclosure of transferred financial assets that are not derecognised in their entirety [line items]
Interest rates on advances received	0.84%	0.84%	0.84%
Interest Rate On Advances Received Against Trade Receivables Sold [Member] | Standard Chartered Bank [Member]
Disclosure of transferred financial assets that are not derecognised in their entirety [line items]
Interest rates on advances received	0.91%	0.91%	0.91%
Interest Rate On Advances Received Against Trade Receivables Sold [Member] | First Commercial Bank [Member]
Disclosure of transferred financial assets that are not derecognised in their entirety [line items]
Interest rates on advances received	1.95%	1.95%	1.95%	2.20%

Trade Receivables, Net - Tra_2

Trade Receivables, Net - Transfer of Financial Asset (Parenthetical) (Detail) $ in Thousands	Dec. 31, 2020USD ($)
Citi Bank Taiwan Limited [Member]
Disclosure of transferred financial assets that are not derecognised in their entirety [line items]
Promissory notes issued	$ 2,000

Inventories - Summary of Invent

Inventories - Summary of Inventories (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Classes of current inventories [abstract]
Finished goods	$ 8,788,460	$ 312,979	$ 7,174,716
Work in process	6,816,602	242,757	2,952,182
Raw materials	29,428,008	1,048,006	20,996,346
Supplies	2,691,779	95,861	2,229,576
Raw materials and supplies in transit	791,610	28,191	530,930
Inventories	$ 48,516,459	$ 1,727,794	$ 33,883,750

Inventories - Additional Inform

Inventories - Additional Information (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Classes of current inventories [abstract]
Cost of inventories recognized as operating costs	$ 398,068,260	$ 14,176,220	$ 347,877,603	$ 309,020,850
Write-downs of inventories	$ 1,493,793	$ 53,198	$ 452,134	$ 980,927

Inventories Related to Real E_3

Inventories Related to Real Estate Business - Summary of Inventories Related to Real Estate Business (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Disclosure of detailed information about property, plant and equipment [Line Items]
Inventories related to real estate business	$ 13,471,645	$ 479,760	$ 11,416,726
Land and buildings held for sale [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Inventories related to real estate business	625,791	22,286	9,983
Construction in progress and machinery in transit [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Inventories related to real estate business	11,058,328	393,815	9,619,217
Land held for construction [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Inventories related to real estate business	$ 1,787,526	$ 63,659	$ 1,787,526

Inventories Related to Real E_4

Inventories Related to Real Estate Business - Additional Information (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Disclosure of detailed information about property, plant and equipment [Line Items]
Inventories related to real estate business expected to be recovered longer than twelve months	$ 13,471,645	$ 479,759	$ 11,416,726

Other Financial Assets - Summar

Other Financial Assets - Summary of Other Financial Assets (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Disclosure of financial assets [Line Items]
Other financial assets	$ 1,082,000	$ 38,533	$ 1,325,327
Current	551,655	19,646	765,834
Non-current	530,345	18,887	559,493
Time deposits with original maturity of over three months [member]
Disclosure of financial assets [Line Items]
Other financial assets	35,988	1,282	25,885
Guaranty deposits [member]
Disclosure of financial assets [Line Items]
Other financial assets	516,505	18,394	661,667
Pledged time deposits [member]
Disclosure of financial assets [Line Items]
Other financial assets	367,550	13,089	620,817
Others [member]
Disclosure of financial assets [Line Items]
Other financial assets	$ 161,957	$ 5,768	$ 16,958

Investments Accounted for Usi_3

Investments Accounted for Using the Equity Method - Summary of Investments Accounted for Using the Equity Method (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Investments in subsidiaries, joint ventures and associates [abstract]
Investments in associates	$ 12,335,239	$ 439,289	$ 11,805,505
Investments in joint ventures	471,434	16,789	279,702
Investments accounted for using the equity method	$ 12,806,673	$ 456,078	$ 12,085,207	$ 9,312,308

Investments Accounted for Usi_4

Investments Accounted for Using the Equity Method - Summary of Investments in Associates Accounted for Using the Equity Method (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2020USD ($)
Disclosure of associates and joint ventures [line items]
Investments in associates	$ 12,335,239	$ 11,805,505	$ 439,289
Yann Yuan Investment Co., Ltd. [member]
Disclosure of associates and joint ventures [line items]
Main Business	Engaged in investing activities
Operating Location	R.O.C.
Percentages of ownership held by the Group	32.21%	32.21%
ChipMOS Technologies Inc. [member]
Disclosure of associates and joint ventures [line items]
Main Business	Engaged in the packaging and testing of semiconductors
Operating Location	R.O.C.
Percentages of ownership held by the Group	10.85%	20.48%
M-Universe Investments Pte. Ltd. [member]
Disclosure of associates and joint ventures [line items]
Main Business	Investment company
Operating Location	Singapore
Percentages of ownership held by the Group	42.23%	42.23%
Hung Ching Development & Construction Co. [member]
Disclosure of associates and joint ventures [line items]
Main Business	Engaged in the development, construction and leasing of real estate properties
Operating Location	R.O.C.
Percentages of ownership held by the Group	26.22%	26.22%
Hung Ching Kwan Co. [member]
Disclosure of associates and joint ventures [line items]
Main Business	Engaged in the leasing of real estate properties
Operating Location	R.O.C.
Percentages of ownership held by the Group	27.31%	27.31%
Deca Technologies Inc. [member]
Disclosure of associates and joint ventures [line items]
Main Business	Holding company and the group engaged in manufacturing, development and marketing of wafer level packaging and interconnect technology
Operating Location	British Cayman Islands
Percentages of ownership held by the Group	17.85%	22.02%
Cost [member]
Disclosure of associates and joint ventures [line items]
Investments in associates before deferred gain on transfer of land	$ 12,635,388	$ 12,105,654	449,978
Cost [member] | Yann Yuan Investment Co., Ltd. [member]
Disclosure of associates and joint ventures [line items]
Investments in associates before deferred gain on transfer of land	6,670,035	3,934,190	237,537
Cost [member] | ChipMOS Technologies Inc. [member]
Disclosure of associates and joint ventures [line items]
Investments in associates before deferred gain on transfer of land	2,406,843	4,370,075	85,714
Cost [member] | M-Universe Investments Pte. Ltd. [member]
Disclosure of associates and joint ventures [line items]
Investments in associates before deferred gain on transfer of land	1,848,588	1,814,699	65,833
Cost [member] | Hung Ching Development & Construction Co. [member]
Disclosure of associates and joint ventures [line items]
Investments in associates before deferred gain on transfer of land	1,352,760	1,380,162	48,175
Cost [member] | Hung Ching Kwan Co. [member]
Disclosure of associates and joint ventures [line items]
Investments in associates before deferred gain on transfer of land	270,087	283,105	9,618
Cost [member] | Deca Technologies Inc. [member]
Disclosure of associates and joint ventures [line items]
Investments in associates before deferred gain on transfer of land	87,075	323,423	3,101
Deferred gain on transfer of land [member]
Disclosure of associates and joint ventures [line items]
Investments in associates	$ 300,149	$ 300,149	$ 10,689

Investments Accounted for Usi_5

Investments Accounted for Using the Equity Method - Additional Information (Detail) $ / shares in Units, ¥ in Thousands, shares in Thousands, $ in Thousands, $ in Thousands

Jun. 30, 2020TWD ($)$ / sharesshares

Jun. 30, 2020USD ($)

Mar. 31, 2019

Apr. 30, 2019TWD ($)

Mar. 31, 2019CNY (¥)

Dec. 31, 2020TWD ($)

Dec. 31, 2020USD ($)

Dec. 31, 2019TWD ($)

Dec. 31, 2018TWD ($)

Dec. 31, 2021TWD ($)

Dec. 31, 2021USD ($)

Dec. 31, 2020USD ($)

Disclosure of Investments Accounted for Using Equity Method [line Items]

Gain on disposal of investments accounted for using the equity method

$ 243,057

Impairment losses on financial assets

$ 400,201

$ 521,010

Investments in joint ventures

$ 471,434

279,702

$ 16,789

Deca Technologies Inc [member]

Disclosure of Investments Accounted for Using Equity Method [line Items]

Gain on disposal of investments accounted for using the equity method

$ 17,180

$ 612

Impairment losses on financial assets

$ 400,201

Percentage of Ownership (%)

17.85%

17.85%

ChipMos Technologies Inc [member]

Disclosure of Investments Accounted for Using Equity Method [line Items]

Gain on disposal of investments accounted for using the equity method

$ 74,117

$ 2,639

Disposal of Ordinary shares | shares

70,000

Percentage of Ownership (%)

10.85%

10.85%

Nominal value per share | $ / shares

$ 32

SUMA-USI Electronics Co., Ltd. [member]

Disclosure of Investments Accounted for Using Equity Method [line Items]

Percentage of ownership interest in joint venture

49.00%

Investments in joint ventures

$ 469,307

$ 16,713

SUMA-USI Electronics Co., Ltd. [member] | Cancon Information Industry Co Ltd [Member]

Disclosure of Investments Accounted for Using Equity Method [line Items]

Consideration paid in cash for shares | ¥

¥ 107,800

Investments Accounted for Usi_6

Investments Accounted for Using the Equity Method - Summary of Fair Values of Investments in Associates with Available Published Price Quotation (Detail) - Level 1 of fair value hierarchy [member] $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Hung Ching Development & Construction Co. [member]
Disclosure of associates and joint ventures [line items]
Fair value of investments in associates with available published price quotation	$ 1,317,692	$ 46,926	$ 1,551,033
ChipMos Technologies Inc [member]
Disclosure of associates and joint ventures [line items]
Fair value of investments in associates with available published price quotation	$ 2,710,572	$ 96,530	$ 5,100,181

Investments Accounted for Usi_7

Investments Accounted for Using the Equity Method - Summary of Aggregate Information of Associates that are Not Individually Material (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Disclosure of associates and joint ventures [line items]
Net profit	$ 28,651,900	$ 1,020,366	$ 18,268,565	$ 27,424,309
Other comprehensive income (loss)	495,313	17,640	(4,370,611)	(852,632)
Total comprehensive income (loss)	29,147,213	1,038,006	13,897,954	26,571,677
Associates that are not individually material [member]
Disclosure of associates and joint ventures [line items]
Net profit	545,833	19,438	321,413	147,535
Other comprehensive income (loss)	2,784,094	99,149	1,401,453	(613,471)
Total comprehensive income (loss)	$ 3,329,927	$ 118,587	$ 1,722,866	$ (465,936)

Investments Accounted for Usi_8

Investments Accounted for Using the Equity Method - Summary of Investments in joint ventures Accounted for using the Equity Method (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2020USD ($)
Disclosure of joint ventures [line items]
Carrying Amount	$ 471,434	$ 279,702	$ 16,789
SUMA-USI Electronics Co., Ltd [member]
Disclosure of joint ventures [line items]
Main Business	Engaged in the design and production of electronic products
Operating Location	China
Carrying Amount	$ 471,434	$ 279,702	$ 16,789
percentages of ownership	49.00%	49.00%

Investments Accounted for Usi_9

Investments Accounted for Using the Equity Method - Summary of Aggregate Information of the Joint Venture that is Not Individually Material (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Disclosure of joint ventures [line items]
Net Loss	$ 28,651,900	$ 1,020,366	$ 18,268,565	$ 27,424,309
Other comprehensive income (loss)	495,313	17,640	(4,370,611)	(852,632)
Total comprehensive income (loss)	29,147,213	1,038,006	13,897,954	26,571,677
Joint venture that is not individually material [member]
Disclosure of joint ventures [line items]
Net Loss	1,780	63	(139,137)	(306,156)
Other comprehensive income (loss)	3,881	138	(3,169)
Total comprehensive income (loss)	$ 5,661	$ 201	$ (142,306)	$ (306,156)

Property, Plant and Equipment -

Property, Plant and Equipment - Summary of Property, Plant and Equipment (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning balance	$ 232,093,327
Depreciation expense	46,016,548	$ 1,638,766	$ 45,240,667	$ 39,893,786
Additions	59,024,201	2,102,001	63,073,887	39,092,238
Ending balance	233,207,324	8,305,104	232,093,327
Cost [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning balance	576,444,907	20,528,666		370,320,242
Additions	59,024,201	2,102,001	63,073,887	39,092,238
Disposals	(15,730,635)	(560,209)	(22,630,764)	(29,456,450)
Disposal Of Subsidiaries	(8,127,308)	(289,434)
Reclassification	538,074	19,162	745,331	(14,891)
Acquisition through business combinations	5,917,803	210,748	7,034,875	156,721,779
Effect of foreign currency exchange differences	(2,861,733)	(101,913)	(6,782,466)	(1,200,829)
Ending balance	615,205,309	21,909,021	576,444,907
Cost [member] | Previously stated [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning balance			535,462,089
Ending balance				535,462,089
Cost [member] | Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning balance			535,004,044
Ending balance				535,004,044
Accumulated depreciation, amortisation and impairment [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning balance	344,351,580	12,263,233		235,151,836
Depreciation expense	46,016,548	1,638,766	45,240,667	39,893,786
Impairment losses recognized	992,273	35,337	201,006	133,071
Disposals	(11,006,578)	(391,972)	(22,024,853)	(28,266,113)
Disposal Of Subsidiaries	(580,895)	(20,687)
Reclassification	311,848	11,106	294,232	(265)
Acquisition through business combinations	4,187,020	149,110	4,465,048	74,736,157
Effect of foreign currency exchange differences	(2,273,811)	(80,976)	(4,513,055)	(778,971)
Ending balance	381,997,985	13,603,917	344,351,580
Accumulated depreciation, amortisation and impairment [member] | Previously stated [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning balance			320,869,501
Ending balance				320,869,501
Accumulated depreciation, amortisation and impairment [member] | Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning balance			320,688,535
Ending balance				320,688,535
Land [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning balance	10,333,822
Ending balance	10,336,568	368,112	10,333,822
Land [member] | Cost [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning balance	10,333,822	368,014		3,258,518
Acquisition through business combinations	46,388	1,652	189,111	6,880,400
Effect of foreign currency exchange differences	(43,642)	(1,554)	(21,258)	27,051
Ending balance	10,336,568	368,112	10,333,822
Land [member] | Cost [member] | Previously stated [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning balance			10,165,969
Ending balance				10,165,969
Land [member] | Cost [member] | Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning balance			10,165,969
Ending balance				10,165,969
Buildings and improvements [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning balance	85,409,580
Ending balance	82,273,186	2,929,957	85,409,580
Buildings and improvements [member] | Cost [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning balance	153,972,960	5,483,368		100,187,928
Additions	86,409	3,077	806,844	144,898
Disposals	(365,758)	(13,026)	(983,690)	(677,206)
Disposal Of Subsidiaries	(3,665,811)	(130,549)
Reclassification	7,367,875	262,389	13,601,469	5,388,709
Acquisition through business combinations	1,142,690	40,694	1,044,383	37,127,957
Effect of foreign currency exchange differences	(266,536)	(9,492)	(2,204,057)	(464,275)
Ending balance	158,271,829	5,636,461	153,972,960
Buildings and improvements [member] | Cost [member] | Previously stated [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning balance			141,708,011
Ending balance				141,708,011
Buildings and improvements [member] | Cost [member] | Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning balance			141,708,011
Ending balance				141,708,011
Buildings and improvements [member] | Accumulated depreciation, amortisation and impairment [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning balance	68,563,380	2,441,716		41,915,064
Depreciation expense	7,401,223	263,576	6,989,392	6,325,948
Impairment losses recognized	0	0	78,562	29,531
Disposals	(300,832)	(10,713)	(881,149)	(491,033)
Disposal Of Subsidiaries	(153,002)	(5,449)
Reclassification	3,462	123	210,558	(265)
Acquisition through business combinations	548,190	19,522	445,682	15,097,920
Effect of foreign currency exchange differences	(63,778)	(2,271)	(1,023,739)	(133,091)
Ending balance	75,998,643	2,706,504	68,563,380
Buildings and improvements [member] | Accumulated depreciation, amortisation and impairment [member] | Previously stated [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning balance			62,744,074
Ending balance				62,744,074
Buildings and improvements [member] | Accumulated depreciation, amortisation and impairment [member] | Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning balance			62,744,074
Ending balance				62,744,074
Machinery and equipment1 [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning balance	112,996,670
Ending balance	122,063,883	4,347,004	112,996,670
Machinery and equipment1 [member] | Cost [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning balance	376,745,448	13,416,861		253,198,003
Additions	695,561	24,771	413,008	192,673
Disposals	(12,818,849)	(456,512)	(19,139,634)	(26,493,282)
Disposal Of Subsidiaries	(3,223,448)	(114,795)
Reclassification	52,980,977	1,886,787	41,302,651	32,060,513
Acquisition through business combinations	3,972,397	141,467	5,507,315	95,810,062
Effect of foreign currency exchange differences	(2,459,521)	(87,590)	(5,176,282)	(929,579)
Ending balance	415,892,565	14,810,989	376,745,448
Machinery and equipment1 [member] | Cost [member] | Previously stated [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning balance			353,838,390
Ending balance				353,838,390
Machinery and equipment1 [member] | Cost [member] | Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning balance			353,838,390
Ending balance				353,838,390
Machinery and equipment1 [member] | Accumulated depreciation, amortisation and impairment [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning balance	263,748,778	9,392,763		187,012,805
Depreciation expense	36,373,712	1,295,360	35,747,308	31,751,251
Impairment losses recognized	981,535	34,955	102,056	97,680
Disposals	(8,306,990)	(295,833)	(18,640,266)	(25,704,778)
Disposal Of Subsidiaries	(345,834)	(12,316)
Reclassification	497,230	17,708	83,777
Acquisition through business combinations	3,049,895	108,615	4,000,338	53,210,063
Effect of foreign currency exchange differences	(2,169,644)	(77,267)	(3,294,855)	(616,601)
Ending balance	293,828,682	10,463,985	263,748,778
Machinery and equipment1 [member] | Accumulated depreciation, amortisation and impairment [member] | Previously stated [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning balance			245,750,420
Ending balance				245,750,420
Machinery and equipment1 [member] | Accumulated depreciation, amortisation and impairment [member] | Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning balance			245,750,420
Ending balance				245,750,420
Other equipment [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning balance	6,715,694
Ending balance	4,680,222	166,674	6,715,694
Other equipment [member] | Cost [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning balance	18,755,116	667,917		7,812,080
Additions	47,137	1,678	76,671	84,860
Disposals	(2,419,423)	(86,162)	(2,507,440)	(2,251,060)
Disposal Of Subsidiaries	(445,506)	(15,866)
Reclassification	222,066	7,908	3,062,838	2,148,211
Acquisition through business combinations	702,500	25,018	43,611	11,122,171
Effect of foreign currency exchange differences	(11,008)	(391)	(300,686)	(78,095)
Ending balance	16,850,882	600,102	18,755,116
Other equipment [member] | Cost [member] | Previously stated [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning balance			18,838,167
Ending balance				18,838,167
Other equipment [member] | Cost [member] | Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning balance			18,380,122
Ending balance				18,380,122
Other equipment [member] | Accumulated depreciation, amortisation and impairment [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning balance	12,039,422	428,754		6,223,967
Depreciation expense	2,241,613	79,830	2,503,967	1,816,587
Impairment losses recognized	10,738	382	20,388	5,860
Disposals	(2,398,756)	(85,426)	(2,503,438)	(2,070,302)
Disposal Of Subsidiaries	(82,059)	(2,922)
Reclassification	(188,844)	(6,725)	(103)
Acquisition through business combinations	588,935	20,973	19,028	6,428,174
Effect of foreign currency exchange differences	(40,389)	(1,438)	(194,461)	(29,279)
Ending balance	12,170,660	433,428	12,039,422
Other equipment [member] | Accumulated depreciation, amortisation and impairment [member] | Previously stated [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning balance			12,375,007
Ending balance				12,375,007
Other equipment [member] | Accumulated depreciation, amortisation and impairment [member] | Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning balance			12,194,041
Ending balance				12,194,041
Construction in progress and machinery in transit [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning balance	16,637,561
Ending balance	13,853,465	493,357	16,637,561
Construction in progress and machinery in transit [member] | Cost [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning balance	16,637,561	592,506		5,863,713
Additions	58,195,094	2,072,475	61,777,364	38,669,807
Disposals	(126,605)	(4,509)		(34,902)
Disposal Of Subsidiaries	(792,543)	(28,224)
Reclassification	(60,032,844)	(2,137,922)	(57,221,627)	(39,612,324)
Acquisition through business combinations	53,828	1,917	250,455	5,781,189
Effect of foreign currency exchange differences	(81,026)	(2,886)	919,817	244,069
Ending balance	$ 13,853,465	$ 493,357	16,637,561
Construction in progress and machinery in transit [member] | Cost [member] | Previously stated [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning balance			10,911,552
Ending balance				10,911,552
Construction in progress and machinery in transit [member] | Cost [member] | Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Beginning balance			$ 10,911,552
Ending balance				$ 10,911,552

Property, Plant and Equipment_2

Property, Plant and Equipment - Additional Information (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Accumulated depreciation, amortisation and impairment [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Impairment losses recognized property plant "and" equipment	$ 992,273	$ 35,337	$ 201,006	$ 133,071

Property, Plant and Equipment_3

Property, Plant and Equipment - Summary of Property, Plant and Equipment Depreciated Useful Lives (Detail) - Buildings and improvements [member]	12 Months Ended
	Dec. 31, 2020
Bottom of range [member] | Main plant buildings [Member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Property, plant and equipment useful lives	10
Bottom of range [member] | Cleanrooms [Member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Property, plant and equipment useful lives	10
Bottom of range [member] | Others [Member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Property, plant and equipment useful lives	3
Bottom of range [member] | Machinery and equipment1 [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Property, plant and equipment useful lives	2
Bottom of range [member] | Other equipment [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Property, plant and equipment useful lives	2
Top of range [member] | Main plant buildings [Member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Property, plant and equipment useful lives	55
Top of range [member] | Cleanrooms [Member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Property, plant and equipment useful lives	20
Top of range [member] | Others [Member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Property, plant and equipment useful lives	20
Top of range [member] | Machinery and equipment1 [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Property, plant and equipment useful lives	10
Top of range [member] | Other equipment [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Property, plant and equipment useful lives	20

Lease Arrangements - Summary of

Lease Arrangements - Summary of Right-of-Use Assets (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2020USD ($)
Disclosure of quantitative information about right-of-use assets [line items]
Carrying amounts	$ 8,620,612		$ 9,792,221	$ 307,002
Additions to right-of-use assets	702,996	$ 25,035	824,268
Depreciation charge for right-of-use assets	946,880	33,721	1,055,458
Land [member]
Disclosure of quantitative information about right-of-use assets [line items]
Carrying amounts	5,840,779		7,036,887	208,005
Depreciation charge for right-of-use assets	214,682	7,645	215,301
Buildings and improvements [member]
Disclosure of quantitative information about right-of-use assets [line items]
Carrying amounts	2,548,838		2,121,797	90,771
Depreciation charge for right-of-use assets	370,458	13,193	307,708
Machinery and equipment [member]
Disclosure of quantitative information about right-of-use assets [line items]
Carrying amounts	181,065		588,443	6,448
Depreciation charge for right-of-use assets	335,039	11,932	507,443
Other equipment [member]
Disclosure of quantitative information about right-of-use assets [line items]
Carrying amounts	49,930		45,094	$ 1,778
Depreciation charge for right-of-use assets	$ 26,701	$ 951	$ 25,006

Lease Arrangements - Summary _2

Lease Arrangements - Summary of Lease Liabilities (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Lease liabilities [abstract]
Current	$ 774,444	$ 27,580	$ 632,802
Non-current	$ 5,101,386	$ 181,673	$ 5,176,123

Lease Arrangements - Summary _3

Lease Arrangements - Summary of the Group's Lease Liabilities are Mainly From Land and Buildings and Improvements. Range of Discount Rate for Lease Liabilities (Detail)	Dec. 31, 2020	Dec. 31, 2019
Land [member] | Bottom of range [member]
Disclosure of detailed information about property, plant and equipment [line items]
Discount Rate For Lease Liabilities	0.54%	0.54%
Land [member] | Top of range [member]
Disclosure of detailed information about property, plant and equipment [line items]
Discount Rate For Lease Liabilities	8.00%	4.90%
Buildings and improvements [member] | Bottom of range [member]
Disclosure of detailed information about property, plant and equipment [line items]
Discount Rate For Lease Liabilities	0.54%	0.30%
Buildings and improvements [member] | Top of range [member]
Disclosure of detailed information about property, plant and equipment [line items]
Discount Rate For Lease Liabilities	8.84%	8.62%

Lease Arrangements - Additional

Lease Arrangements - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2020
Land [member] | Bottom of range [member]
Disclosure of detailed information about property, plant and equipment [line items]
Lease Term	1 year
Land [member] | Top of range [member]
Disclosure of detailed information about property, plant and equipment [line items]
Lease Term	54 years
Buildings [member] | Bottom of range [member]
Disclosure of detailed information about property, plant and equipment [line items]
Lease Term	1 year
Buildings [member] | Top of range [member]
Disclosure of detailed information about property, plant and equipment [line items]
Lease Term	30 years

Lease Arrangements - Summary _4

Lease Arrangements - Summary of Other Related Lease Information (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Disclosure of detailed information about property, plant and equipment [abstract]
Expenses relating to short-term leases	$ 682,142	$ 24,293	$ 421,924
Expenses relating to low-value assets leases	5,433	193	4,473
Expenses relating to variable lease payments not included in the measurement of lease liabilities	43,112	1,535	53,403
Total cash outflow for leases	$ (1,854,456)	$ (66,042)	$ (1,511,277)

Investment Properties - Summary

Investment Properties - Summary of Investment Properties (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018TWD ($)
Disclosure of detailed information about investment property [line items]
Beginning balance	$ 12,854,071		$ 7,738,379
Depreciation expenses	562,260	$ 20,023	594,110		$ 392,667
Ending balance	12,538,083	446,513	12,854,071		7,738,379
Land [member]
Disclosure of detailed information about investment property [line items]
Beginning balance	35,965		35,965
Ending balance	35,965	1,281	35,965		35,965
Buildings and improvements [member]
Disclosure of detailed information about investment property [line items]
Beginning balance	6,737,798		7,702,414
Ending balance	6,480,338	230,781	6,737,798		7,702,414
Right-of-use assets [member]
Disclosure of detailed information about investment property [line items]
Beginning balance	6,080,308
Ending balance	6,021,780	214,451	6,080,308
Cost [member]
Disclosure of detailed information about investment property [line items]
Beginning balance	14,314,126	509,763	14,314,126		8,442,750
Additions	6,352	226	2,532		125,853
Disposals	(1,902)	(68)	(1,843)
Reclassification	42,317	1,507	(511,199)		14,891
Effects of foreign currency exchange differences	236,790	8,433	(513,066)		(137,739)
Ending balance	14,597,683	519,861	14,314,126	$ 509,763	14,314,126
Cost [member] | Previously stated [member]
Disclosure of detailed information about investment property [line items]
Beginning balance			8,445,755
Ending balance					8,445,755
Cost [member] | Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of detailed information about investment property [line items]
Beginning balance				15,337,702
Ending balance
Cost [member] | Land [member]
Disclosure of detailed information about investment property [line items]
Beginning balance	35,965	1,281			35,965
Ending balance	35,965	1,281	35,965	1,281
Cost [member] | Land [member] | Previously stated [member]
Disclosure of detailed information about investment property [line items]
Beginning balance			35,965
Ending balance					35,965
Cost [member] | Land [member] | Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of detailed information about investment property [line items]
Beginning balance				35,965
Ending balance
Cost [member] | Buildings and improvements [member]
Disclosure of detailed information about investment property [line items]
Beginning balance	7,710,369	274,586	7,710,369		8,406,785
Additions	6,352	226	2,532		125,853
Disposals	(1,902)	(68)	(1,843)
Reclassification	(3,884)	(138)	(490,130)		14,891
Effects of foreign currency exchange differences	111,870	3,984	(209,980)		(137,739)
Ending balance	7,822,805	278,590	7,710,369	274,586	7,710,369
Cost [member] | Buildings and improvements [member] | Previously stated [member]
Disclosure of detailed information about investment property [line items]
Beginning balance			8,409,790
Ending balance					8,409,790
Cost [member] | Buildings and improvements [member] | Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of detailed information about investment property [line items]
Beginning balance				8,409,790
Ending balance
Cost [member] | Right-of-use assets [member]
Disclosure of detailed information about investment property [line items]
Beginning balance	6,567,792	233,896	6,567,792
Reclassification	46,201	1,645	(21,069)
Effects of foreign currency exchange differences	124,920	4,449	(303,086)
Ending balance	6,738,913	239,990	6,567,792	233,896	6,567,792
Cost [member] | Right-of-use assets [member] | Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of detailed information about investment property [line items]
Beginning balance				6,891,947
Ending balance
Accumulated depreciation, amortisation and impairment [member]
Disclosure of detailed information about investment property [line items]
Beginning balance	1,460,055	51,996	1,460,055		323,314
Depreciation expenses	562,260	20,023	594,110		392,667
Disposals	(1,293)	(46)	(1,240)
Reclassification	9,119	325	(209,912)		265
Effects of foreign currency exchange differences	29,459	1,050	76,999		(8,870)
Ending balance	2,059,600	73,348	1,460,055	51,996	1,460,055
Accumulated depreciation, amortisation and impairment [member] | Previously stated [member]
Disclosure of detailed information about investment property [line items]
Beginning balance			707,376
Ending balance					707,376
Accumulated depreciation, amortisation and impairment [member] | Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of detailed information about investment property [line items]
Beginning balance				1,000,098
Ending balance
Accumulated depreciation, amortisation and impairment [member] | Buildings and improvements [member]
Disclosure of detailed information about investment property [line items]
Beginning balance	972,571	34,636	972,571		323,314
Depreciation expenses	353,048	12,573	377,536		392,667
Disposals	(1,293)	(46)	(1,240)
Reclassification	(1,498)	(53)	(210,455)		265
Effects of foreign currency exchange differences	19,639	699	99,354		(8,870)
Ending balance	1,342,467	47,809	972,571	34,636	972,571
Accumulated depreciation, amortisation and impairment [member] | Buildings and improvements [member] | Previously stated [member]
Disclosure of detailed information about investment property [line items]
Beginning balance			707,376
Ending balance					707,376
Accumulated depreciation, amortisation and impairment [member] | Buildings and improvements [member] | Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of detailed information about investment property [line items]
Beginning balance				707,376
Ending balance
Accumulated depreciation, amortisation and impairment [member] | Right-of-use assets [member]
Disclosure of detailed information about investment property [line items]
Beginning balance	487,484	17,360	487,484
Depreciation expenses	209,212	7,450	216,574
Reclassification	10,617	378	543
Effects of foreign currency exchange differences	9,820	351	(22,355)
Ending balance	$ 717,133	$ 25,539	$ 487,484	17,360	$ 487,484
Accumulated depreciation, amortisation and impairment [member] | Right-of-use assets [member] | Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of detailed information about investment property [line items]
Beginning balance				$ 292,722
Ending balance

Investment Properties - Additio

Investment Properties - Additional Information (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)
Disclosure of detailed information about investment property [line items]
Adjustment to rent income	$ 54,139	$ 1,928
Bottom of range [member]
Disclosure of detailed information about investment property [line items]
Operating lease Term	1 year	1 year
Top of range [member]
Disclosure of detailed information about investment property [line items]
Operating lease Term	15 years	15 years

Investment Properties - Summa_2

Investment Properties - Summary of Maturity Analysis Of Operating Lease Payments (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Disclosure of detailed information about investment property [line items]
Undiscounted operating lease payments to be received	$ 3,424,290	$ 121,948	$ 3,848,677
Year 1 [member]
Disclosure of detailed information about investment property [line items]
Undiscounted operating lease payments to be received	880,929	31,372	921,649
Year 2 [member]
Disclosure of detailed information about investment property [line items]
Undiscounted operating lease payments to be received	688,123	24,506	744,366
Year 3 [member]
Disclosure of detailed information about investment property [line items]
Undiscounted operating lease payments to be received	471,966	16,808	623,326
Year 4 [member]
Disclosure of detailed information about investment property [line items]
Undiscounted operating lease payments to be received	383,307	13,651	408,634
Year 5 [member]
Disclosure of detailed information about investment property [line items]
Undiscounted operating lease payments to be received	335,706	11,955	320,611
Year 6 onwards [member]
Disclosure of detailed information about investment property [line items]
Undiscounted operating lease payments to be received	$ 664,259	$ 23,656	$ 830,091

Investment Properties - Investm

Investment Properties - Investment Properties Depreciated on a Straight-Line Basis Over Useful Lives (Detail)	12 Months Ended
	Dec. 31, 2020
Bottom of range [member] | Main plant buildings [Member]
Disclosure of detailed information about investment property [line items]
Investment properties are depreciated using the straight-line method over their estimated useful lives	10
Bottom of range [member] | Right-of-use assets [member]
Disclosure of detailed information about investment property [line items]
Investment properties are depreciated using the straight-line method over their estimated useful lives	15
Top of range [member] | Main plant buildings [Member]
Disclosure of detailed information about investment property [line items]
Investment properties are depreciated using the straight-line method over their estimated useful lives	40
Top of range [member] | Right-of-use assets [member]
Disclosure of detailed information about investment property [line items]
Investment properties are depreciated using the straight-line method over their estimated useful lives	50

Investment Properties - Summa_3

Investment Properties - Summary of Investment Properties, Fair Value (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Disclosure of detailed information about investment property [line items]
Fair value	$ 12,538,083	$ 446,513	$ 12,854,071	$ 7,738,379
Fair value [member] | Level 3 of fair value hierarchy [member]
Disclosure of detailed information about investment property [line items]
Fair value	$ 19,799,714	$ 705,118	$ 19,586,287

Goodwill - Summary of Goodwill

Goodwill - Summary of Goodwill (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Disclosure of reconciliation of changes in goodwill [line items]
Beginning balance	$ 50,198,436	$ 1,787,693	$ 49,974,446	$ 9,934,494
Acquisition through business combinations	4,625,269	164,718	264,977	39,990,231
Effect of foreign currency exchange differences	(46,266)	(1,647)	(40,987)	49,721
Ending balance	54,777,439	1,950,764	50,198,436	49,974,446
Cost [member]
Disclosure of reconciliation of changes in goodwill [line items]
Beginning balance	52,612,549	1,873,666	52,388,559	12,348,607
Acquisition through business combinations	4,625,269	164,718	264,977	39,990,231
Effect of foreign currency exchange differences	(46,266)	(1,647)	(40,987)	49,721
Ending balance	57,191,552	2,036,737	52,612,549	52,388,559
Accumulated impairment [Member]
Disclosure of reconciliation of changes in goodwill [line items]
Beginning balance	2,414,113	85,973	2,414,113	2,414,113
Acquisition through business combinations	0	0
Effect of foreign currency exchange differences	0	0
Ending balance	$ 2,414,113	$ 85,973	$ 2,414,113	$ 2,414,113

Goodwill - Summary of Carrying

Goodwill - Summary of Carrying Amounts of Goodwill Allocated to Cash-generating Units (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018TWD ($)	Dec. 31, 2017TWD ($)
Disclosure of information for cash-generating units [line items]
Goodwill	$ 54,777,439	$ 1,950,764	$ 50,198,436	$ 1,787,693	$ 49,974,446	$ 9,934,494
Packaging segment [member]
Disclosure of information for cash-generating units [line items]
Goodwill	35,703,625	1,271,496	35,717,828
Testing segment [member]
Disclosure of information for cash-generating units [line items]
Goodwill	13,365,068	475,964	13,421,321
EMS Segment Member [Member]
Disclosure of information for cash-generating units [line items]
Goodwill	5,560,645	198,029	903,346
All other segments [member]
Disclosure of information for cash-generating units [line items]
Goodwill	$ 148,101	$ 5,275	$ 155,941

Goodwill - Additional Informati

Goodwill - Additional Information (Detail) - TWD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of reconciliation of changes in goodwill [line items]
Impairment loss on goodwill	$ 0	$ 0	$ 0
Bottom of range [member]
Disclosure of reconciliation of changes in goodwill [line items]
Discount rate applied to cash flow projections	10.39%	9.59%	9.74%
Top of range [member]
Disclosure of reconciliation of changes in goodwill [line items]
Discount rate applied to cash flow projections	(14.71%)	(14.99%)	10.22%

Other Intangible Assets - Summa

Other Intangible Assets - Summary of Carrying Amounts of Each Class of Other Intangible Assets (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Disclosure of detailed information about intangible assets [line items]
Beginning balance	$ 29,024,392
Additions	982,655	$ 34,995	$ 1,350,908	$ 537,659
Amortization expense	3,733,377	132,955	3,576,606	2,402,450
Disposal of subsidiaries	(297,421)	(10,592)
Ending balance	26,808,668	954,725	29,024,392
Cost [member]
Disclosure of detailed information about intangible assets [line items]
Beginning balance	36,993,875	1,317,446		5,190,328
Additions	982,655	34,995	1,350,908	537,659
Disposals or derecognization	(70,007)	(2,493)	(2,045,396)	(99,589)
Disposal of subsidiaries	(38,125)	(1,358)
Acquisition through business combinations	1,669,025	59,438	752,548	31,507,668
Effect of foreign currency exchange differences	(84,755)	(3,018)	(52,879)	4,969
Ending balance	39,452,668	1,405,010	36,993,875
Cost [member] | Previously stated [member]
Disclosure of detailed information about intangible assets [line items]
Beginning balance			37,141,035
Ending balance				37,141,035
Cost [member] | Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of detailed information about intangible assets [line items]
Beginning balance			36,988,694
Ending balance				36,988,694
Accumulated depreciation and amortization [Member]
Disclosure of detailed information about intangible assets [line items]
Beginning balance	7,969,483	283,813		3,783,463
Amortization expense	3,733,377	132,955	3,576,606	2,402,450
Disposals or derecognization	(52,389)	(1,866)	(2,038,462)	(99,433)
Disposal of subsidiaries	(10,688)	(381)
Acquisition through business combinations	1,026,187	36,545	321,187	153,282
Effect of foreign currency exchange differences	(21,970)	(781)	(40,509)	3,573
Ending balance	12,644,000	450,285	7,969,483
Accumulated depreciation and amortization [Member] | Previously stated [member]
Disclosure of detailed information about intangible assets [line items]
Beginning balance			6,243,335
Ending balance				6,243,335
Accumulated depreciation and amortization [Member] | Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of detailed information about intangible assets [line items]
Beginning balance			6,150,661
Ending balance				6,150,661
Customer relationships [Member]
Disclosure of detailed information about intangible assets [line items]
Beginning balance	9,333,333
Ending balance	8,334,203	296,802	9,333,333
Customer relationships [Member] | Cost [member]
Disclosure of detailed information about intangible assets [line items]
Beginning balance	11,000,001	391,738		915,636
Additions	0
Disposals or derecognization	0		(915,635)
Acquisition through business combinations	103,633	3,691		11,000,000
Effect of foreign currency exchange differences	552	20
Ending balance	11,104,186	395,449	11,000,001
Customer relationships [Member] | Cost [member] | Previously stated [member]
Disclosure of detailed information about intangible assets [line items]
Beginning balance			11,915,636
Ending balance				11,915,636
Customer relationships [Member] | Cost [member] | Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of detailed information about intangible assets [line items]
Beginning balance			11,915,636
Ending balance				11,915,636
Customer relationships [Member] | Accumulated depreciation and amortization [Member]
Disclosure of detailed information about intangible assets [line items]
Beginning balance	1,666,668	59,354		801,860
Amortization expense	1,000,000	35,613	1,033,464	746,979
Disposals or derecognization	0		(915,635)
Acquisition through business combinations	102,768	3,660
Effect of foreign currency exchange differences	547	19
Ending balance	2,769,983	98,646	1,666,668
Customer relationships [Member] | Accumulated depreciation and amortization [Member] | Previously stated [member]
Disclosure of detailed information about intangible assets [line items]
Beginning balance			1,548,839
Ending balance				1,548,839
Customer relationships [Member] | Accumulated depreciation and amortization [Member] | Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of detailed information about intangible assets [line items]
Beginning balance			1,548,839
Ending balance				1,548,839
Computer software [Member]
Disclosure of detailed information about intangible assets [line items]
Beginning balance	1,929,539
Ending balance	2,678,867	95,401	1,929,539
Computer software [Member] | Cost [member]
Disclosure of detailed information about intangible assets [line items]
Beginning balance	4,606,878	164,063		3,686,452
Additions	951,439	33,883	1,358,533	528,883
Disposals or derecognization	(55,413)	(1,973)	(1,123,446)	(95,358)
Disposal of subsidiaries	(38,125)	(1,358)
Acquisition through business combinations	1,451,123	51,678	19,944	274,868
Effect of foreign currency exchange differences	(66,459)	(2,367)	(49,198)	6,200
Ending balance	6,849,443	243,926	4,606,878
Computer software [Member] | Cost [member] | Previously stated [member]
Disclosure of detailed information about intangible assets [line items]
Beginning balance			4,401,045
Ending balance				4,401,045
Computer software [Member] | Cost [member] | Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of detailed information about intangible assets [line items]
Beginning balance			4,401,045
Ending balance				4,401,045
Computer software [Member] | Accumulated depreciation and amortization [Member]
Disclosure of detailed information about intangible assets [line items]
Beginning balance	2,677,339	95,347		2,822,121
Amortization expense	729,330	25,973	583,300	373,536
Disposals or derecognization	(47,345)	(1,686)	(1,116,512)	(95,202)
Disposal of subsidiaries	(10,688)	(381)
Acquisition through business combinations	843,746	30,048	7,765	137,799
Effect of foreign currency exchange differences	(21,806)	(776)	(38,577)	3,109
Ending balance	4,170,576	148,525	2,677,339
Computer software [Member] | Accumulated depreciation and amortization [Member] | Previously stated [member]
Disclosure of detailed information about intangible assets [line items]
Beginning balance			3,241,363
Ending balance				3,241,363
Computer software [Member] | Accumulated depreciation and amortization [Member] | Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of detailed information about intangible assets [line items]
Beginning balance			3,241,363
Ending balance				3,241,363
Patents and acquired specific technology [Member]
Disclosure of detailed information about intangible assets [line items]
Beginning balance	17,718,523
Ending balance	15,720,213	559,837	17,718,523
Patents and acquired specific technology [Member] | Cost [member]
Disclosure of detailed information about intangible assets [line items]
Beginning balance	21,318,696	759,213		389,486
Additions	171	6
Disposals or derecognization	0			(231)
Acquisition through business combinations	0		732,604	20,200,000
Effect of foreign currency exchange differences	312	11	(2,264)	(899)
Ending balance	21,319,179	759,230	21,318,696
Patents and acquired specific technology [Member] | Cost [member] | Previously stated [member]
Disclosure of detailed information about intangible assets [line items]
Beginning balance			20,588,356
Ending balance				20,588,356
Patents and acquired specific technology [Member] | Cost [member] | Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of detailed information about intangible assets [line items]
Beginning balance			20,588,356
Ending balance				20,588,356
Patents and acquired specific technology [Member] | Accumulated depreciation and amortization [Member]
Disclosure of detailed information about intangible assets [line items]
Beginning balance	3,600,173	128,211		70,084
Amortization expense	1,998,554	71,173	1,955,703	1,263,309
Disposals or derecognization	0			(231)
Acquisition through business combinations	0		313,422
Effect of foreign currency exchange differences	239	9	(1,639)	(475)
Ending balance	5,598,966	199,393	3,600,173
Patents and acquired specific technology [Member] | Accumulated depreciation and amortization [Member] | Previously stated [member]
Disclosure of detailed information about intangible assets [line items]
Beginning balance			1,332,687
Ending balance				1,332,687
Patents and acquired specific technology [Member] | Accumulated depreciation and amortization [Member] | Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of detailed information about intangible assets [line items]
Beginning balance			1,332,687
Ending balance				1,332,687
Others [Member]
Disclosure of detailed information about intangible assets [line items]
Beginning balance	42,997
Ending balance	75,385	2,685	42,997
Others [Member] | Cost [member]
Disclosure of detailed information about intangible assets [line items]
Beginning balance	68,300	2,432		198,754
Additions	31,045	1,106		8,776
Additions			(7,625)
Disposals or derecognization	(14,594)	(520)	(6,315)	(4,000)
Acquisition through business combinations	114,269	4,069		32,800
Effect of foreign currency exchange differences	(19,160)	(682)	(1,417)	(332)
Ending balance	179,860	6,405	68,300
Others [Member] | Cost [member] | Previously stated [member]
Disclosure of detailed information about intangible assets [line items]
Beginning balance			235,998
Ending balance				235,998
Others [Member] | Cost [member] | Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of detailed information about intangible assets [line items]
Beginning balance			83,657
Ending balance				83,657
Others [Member] | Accumulated depreciation and amortization [Member]
Disclosure of detailed information about intangible assets [line items]
Beginning balance	25,303	901		89,398
Amortization expense	5,493	196	4,139	18,626
Disposals or derecognization	(5,044)	(180)	(6,315)	(4,000)
Acquisition through business combinations	79,673	2,837		15,483
Effect of foreign currency exchange differences	(950)	(33)	(293)	939
Ending balance	$ 104,475	$ 3,721	25,303
Others [Member] | Accumulated depreciation and amortization [Member] | Previously stated [member]
Disclosure of detailed information about intangible assets [line items]
Beginning balance			120,446
Ending balance				120,446
Others [Member] | Accumulated depreciation and amortization [Member] | Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of detailed information about intangible assets [line items]
Beginning balance			$ 27,772
Ending balance				$ 27,772

Other Intangible Assets - Sum_2

Other Intangible Assets - Summary of Other Intangible Assets Useful Lives (Detail)	12 Months Ended
	Dec. 31, 2020
Customer relationships [Member]
Disclosure of intangible assets with indefinite useful life [line items]
Other intangible assets useful lives	11 years
Bottom of range [member] | Computer software [Member]
Disclosure of intangible assets with indefinite useful life [line items]
Other intangible assets useful lives	2 years
Bottom of range [member] | Patents and acquired specific technology [Member]
Disclosure of intangible assets with indefinite useful life [line items]
Other intangible assets useful lives	5 years
Bottom of range [member] | Others [Member]
Disclosure of intangible assets with indefinite useful life [line items]
Other intangible assets useful lives	5 years
Top of range [member] | Computer software [Member]
Disclosure of intangible assets with indefinite useful life [line items]
Other intangible assets useful lives	10 years
Top of range [member] | Patents and acquired specific technology [Member]
Disclosure of intangible assets with indefinite useful life [line items]
Other intangible assets useful lives	17 years
Top of range [member] | Others [Member]
Disclosure of intangible assets with indefinite useful life [line items]
Other intangible assets useful lives	32 years

Borrowings - Summary of Short T

Borrowings - Summary of Short Term Borrowings (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Disclosure of detailed information about borrowings [line items]
Less: financial liabilities for hedging - current	$ (5,277,325)	$ (187,939)	$ (3,233,301)
Short-term borrowings	31,290,839	1,114,346	37,339,028
Short Term Bank Loans [Member]
Disclosure of detailed information about borrowings [line items]
Secured bank loans, annual interest rate was 0.90%-1.87% as of December 31, 2020	300,495	10,701
Unsecured bank loans, annual interest rates were 0.70%-5.40% and 0.58%-3.83% as of December 31, 2019 and 2020, respectively	34,297,362	1,221,416	40,572,329
Borrowings	34,597,857	1,232,117	40,572,329
Less: financial liabilities for hedging - current	3,307,018	117,771	3,233,301
Short-term borrowings	$ 31,290,839	$ 1,114,346	$ 37,339,028

Borrowings - Summary of Short_2

Borrowings - Summary of Short Term Borrowings (Parenthetical) (Detail)	Dec. 31, 2020	Dec. 31, 2019
Secured Loan [Member] | Bottom of range [member]
Disclosure of detailed information about borrowings [line items]
Annual interest rates	0.90%
Secured Loan [Member] | Top of range [member]
Disclosure of detailed information about borrowings [line items]
Annual interest rates	1.87%
Unsecured Loan [Member] | Bottom of range [member]
Disclosure of detailed information about borrowings [line items]
Annual interest rates	0.58%	0.70%
Unsecured Loan [Member] | Top of range [member]
Disclosure of detailed information about borrowings [line items]
Annual interest rates	3.83%	5.40%

Borrowings - Summary of Bank Lo

Borrowings - Summary of Bank Loans (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Disclosure of detailed information about borrowings [line items]
Less: current portion	$ 2,250,121	$ 80,133	$ 5,112,768
Financial liabilities for hedging - current	5,277,325	187,939	3,233,301
Noncurrent portion	102,259,378	3,641,716	135,965,830
Bank loans [member]
Disclosure of detailed information about borrowings [line items]
Long-term borrowings	107,392,223	3,824,510	130,085,354
Less: current portion	2,250,121	80,133	5,017,970
Financial liabilities for hedging - current	1,970,307	70,168
Financial liabilities for hedging - non-current	5,910,919	210,503
Noncurrent portion	97,260,876	3,463,706	125,067,384
Bank loans [member] | Cost [member]
Disclosure of detailed information about borrowings [line items]
Long-term borrowings	107,496,546	3,828,225	130,095,646
Bank loans [member] | Cost [member] | Syndicated bank loans [Member]
Disclosure of detailed information about borrowings [line items]
Long-term borrowings	12,536,424	446,454	20,000,000
Bank loans [member] | Cost [member] | Other loans [Member]
Disclosure of detailed information about borrowings [line items]
Long-term borrowings	84,146,125	2,996,657	105,214,824
Bank loans [member] | Cost [member] | Mortgage loans [Member]
Disclosure of detailed information about borrowings [line items]
Long-term borrowings	10,813,997	385,114	4,880,822
Bank loans [member] | Net Unamortized Debt Issue Costs [member]
Disclosure of detailed information about borrowings [line items]
Long-term borrowings	$ 104,323	$ 3,715	$ 10,292

Borrowings - Summary of Bank _2

Borrowings - Summary of Bank Loans (Parenthetical) (Detail)	Dec. 31, 2020	Dec. 31, 2019
Syndicated bank loans [Member]
Disclosure of detailed information about borrowings [line items]
Annual interest rates		1.80%
Syndicated bank loans [Member] | Bottom of range [member]
Disclosure of detailed information about borrowings [line items]
Annual interest rates	1.15%
Syndicated bank loans [Member] | Top of range [member]
Disclosure of detailed information about borrowings [line items]
Annual interest rates	1.17%
Other loans [Member] | Bottom of range [member]
Disclosure of detailed information about borrowings [line items]
Annual interest rates	0.56%	0.82%
Other loans [Member] | Top of range [member]
Disclosure of detailed information about borrowings [line items]
Annual interest rates	4.15%	4.13%
Mortgage loans [Member] | Bottom of range [member]
Disclosure of detailed information about borrowings [line items]
Annual interest rates	1.90%	2.43%
Mortgage loans [Member] | Top of range [member]
Disclosure of detailed information about borrowings [line items]
Annual interest rates	4.90%	4.90%

Borrowings - Summary of Bills P

Borrowings - Summary of Bills Payable (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Disclosure of detailed information about borrowings [line items]
Long-term bills payable	$ 4,998,502	$ 178,010	$ 10,895,365
Unamortized Discounts [member]
Disclosure of detailed information about borrowings [line items]
Long-term bills payable	1,498	53	4,635
Longterm Bills Payable [member]
Disclosure of detailed information about borrowings [line items]
Long-term bills payable	5,000,000	178,063	10,900,000
Ta Ching Bills Finance Corporation [member]
Disclosure of detailed information about borrowings [line items]
Long-term bills payable	1,000,000	35,613	3,100,000
Mega Bills Finance Corporation [Member]
Disclosure of detailed information about borrowings [line items]
Long-term bills payable	2,000,000	71,225	2,000,000
China Bills Finance Corporation [member]
Disclosure of detailed information about borrowings [line items]
Long-term bills payable	$ 2,000,000	$ 71,225	2,800,000
International Bills Finance Corporation [member]
Disclosure of detailed information about borrowings [line items]
Long-term bills payable			$ 3,000,000

Borrowings - Summary of Bills_2

Borrowings - Summary of Bills Payable (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Ta Ching Bills Finance Corporation [member]
Disclosure of detailed information about borrowings [line items]
Annual interest rates	0.91%
Borrowings maturity	March 2022
Ta Ching Bills Finance Corporation [member] | Bottom of range [member]
Disclosure of detailed information about borrowings [line items]
Annual interest rates		1.01%
Ta Ching Bills Finance Corporation [member] | Top of range [member]
Disclosure of detailed information about borrowings [line items]
Annual interest rates		1.03%
Mega Bills Finance Corporation [Member]
Disclosure of detailed information about borrowings [line items]
Annual interest rates		1.04%
Borrowings maturity	March 2022
Mega Bills Finance Corporation [Member] | Bottom of range [member]
Disclosure of detailed information about borrowings [line items]
Annual interest rates	0.92%
Mega Bills Finance Corporation [Member] | Top of range [member]
Disclosure of detailed information about borrowings [line items]
Annual interest rates	0.93%
China Bills Finance Corporation [member]
Disclosure of detailed information about borrowings [line items]
Borrowings maturity	March 2022 to December 2022
China Bills Finance Corporation [member] | Bottom of range [member]
Disclosure of detailed information about borrowings [line items]
Annual interest rates	0.65%	1.02%
China Bills Finance Corporation [member] | Top of range [member]
Disclosure of detailed information about borrowings [line items]
Annual interest rates	0.90%	1.05%
International Bills Finance Corporation [member]
Disclosure of detailed information about borrowings [line items]
Borrowings maturity	March 2020 to June 2020
International Bills Finance Corporation [member] | Bottom of range [member]
Disclosure of detailed information about borrowings [line items]
Annual interest rates		1.02%
International Bills Finance Corporation [member] | Top of range [member]
Disclosure of detailed information about borrowings [line items]
Annual interest rates		1.05%

Borrowings - Summary of Long-te

Borrowings - Summary of Long-term Notes Payable (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Disclosure Of Long Term Notes Payable [Line Items]
Bonds issued	$ 56,253,554	$ 2,003,332	$ 36,522,155
Less: current portion			94,798
Bonds payable	$ 49,253,603	$ 1,754,046	36,272,155
Unamortized Discounts [member]
Disclosure Of Long Term Notes Payable [Line Items]
Less: unamortized discounts			2,137
Bonds issued			97,879
Bonds payable			3,081
Commercial Papers [Member]
Disclosure Of Long Term Notes Payable [Line Items]
Bonds payable			$ 100,016
Long Term Notes Payable [Member] | Bottom of range [member]
Disclosure Of Long Term Notes Payable [Line Items]
Annual interest rates			5.02%
Long Term Notes Payable [Member] | Top of range [member]
Disclosure Of Long Term Notes Payable [Line Items]
Annual interest rates			6.89%

Bonds Payable - Summary of Bond

Bonds Payable - Summary of Bonds Payable (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Disclosure of detailed information about borrowings [line items]
Bonds payable	$ 56,253,554	$ 2,003,332	$ 36,522,155
Noncurrent portion	49,253,603	1,754,046	36,272,155
Less: current portion of bonds payable	6,999,951	249,286	250,000
Cost [member]
Disclosure of detailed information about borrowings [line items]
Bonds payable	56,307,200	2,005,242	36,557,200
Cost [member] | Repayable at maturity in January 2021 [member]
Disclosure of detailed information about borrowings [line items]
Bonds payable	7,000,000	249,288	7,000,000
Cost [member] | Repayable at maturity in January 2023 [member]
Disclosure of detailed information about borrowings [line items]
Bonds payable	2,000,000	71,225	2,000,000
Cost [member] | Repayable at maturity in January 2022 [member]
Disclosure of detailed information about borrowings [line items]
Bonds payable	3,700,000	131,766	3,700,000
Cost [member] | Repayable at maturity in January 2024 [member]
Disclosure of detailed information about borrowings [line items]
Bonds payable	4,300,000	153,134	4,300,000
Cost [member] | Repayable at maturity in April 2024 [Member]
Disclosure of detailed information about borrowings [line items]
Bonds payable	6,500,000	231,481	6,500,000
Cost [member] | Repayable at maturity in April 2026 [Member]
Disclosure of detailed information about borrowings [line items]
Bonds payable	3,500,000	124,644	3,500,000
Cost [member] | Repayable at maturity in April 2025 [Member]
Disclosure of detailed information about borrowings [line items]
Bonds payable	10,000,000	356,125
Cost [member] | Repayable at maturity in October 2022 [Member]
Disclosure of detailed information about borrowings [line items]
Bonds payable	6,204,800	220,969	6,204,800
Cost [member] | Repayable at maturity in October 2024 [Member]
Disclosure of detailed information about borrowings [line items]
Bonds payable	3,102,400	110,484	3,102,400
Cost [member] | Repayable at maturity in December 2020 [Member]
Disclosure of detailed information about borrowings [line items]
Bonds payable	0	0	250,000
Cost [member] | Repayable at maturity in August 2023 [Member]
Disclosure of detailed information about borrowings [line items]
Bonds payable	3,000,000	106,838
Cost [member] | Repayable at maturity in August 2025 [Member]
Disclosure of detailed information about borrowings [line items]
Bonds payable	5,000,000	178,063
Cost [member] | Repayable at maturity in August 2027 [Member]
Disclosure of detailed information about borrowings [line items]
Bonds payable	2,000,000	71,225
Discounts on bonds payable [member]
Disclosure of detailed information about borrowings [line items]
Bonds payable	$ 53,646	$ 1,910	$ 35,045

Bonds Payable - Summary of Bo_2

Bonds Payable - Summary of Bonds Payable (Parenthetical) (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Repayable at maturity in January 2021 [member]
Disclosure of detailed information about borrowings [line items]
Interest rate	1.30%	1.30%
Repayable at maturity in January 2023 [member]
Disclosure of detailed information about borrowings [line items]
Interest rate	1.50%	1.50%
Repayable at maturity in January 2022 [member]
Disclosure of detailed information about borrowings [line items]
Interest rate	1.25%	1.25%
Repayable at maturity in January 2024 [member]
Disclosure of detailed information about borrowings [line items]
Interest rate	1.45%	1.45%
Repayable at maturity in April 2024 [Member]
Disclosure of detailed information about borrowings [line items]
Interest rate	0.90%	0.90%
Repayable at maturity in April 2026 [Member]
Disclosure of detailed information about borrowings [line items]
Interest rate	1.03%	1.03%
Repayable at maturity in October 2022 [Member]
Disclosure of detailed information about borrowings [line items]
Interest rate	2.15%	2.15%
Notional Amount	$ 200,000	$ 200,000
Repayable at maturity in October 2024 [Member]
Disclosure of detailed information about borrowings [line items]
Interest rate	2.50%	2.50%
Notional Amount	$ 100,000	$ 100,000
Repayable at maturity in December 2020 [Member]
Disclosure of detailed information about borrowings [line items]
Interest rate	0.00%	0.00%
Repayable at maturity in April 2025 [Member]
Disclosure of detailed information about borrowings [line items]
Interest rate	0.90%	0.90%
Repayable at maturity in August 2023 [Member]
Disclosure of detailed information about borrowings [line items]
Interest rate	0.72%	0.72%
Repayable at maturity in August 2025 [Member]
Disclosure of detailed information about borrowings [line items]
Interest rate	0.85%	0.85%
Repayable at maturity in August 2027 [Member]
Disclosure of detailed information about borrowings [line items]
Interest rate	0.95%	0.95%

Bonds Payable - Additional Info

Bonds Payable - Additional Information (Detail) $ / shares in Units, $ in Thousands, $ in Thousands	1 Months Ended	12 Months Ended
	Dec. 31, 2017TWD ($)$ / shares	Dec. 31, 2019TWD ($)$ / shares	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Disclosure of detailed information about borrowings [line items]
Bonds payable		$ 36,522,155	$ 56,253,554	$ 2,003,332
Secured Domestic Convertible Bonds [Member]
Disclosure of detailed information about borrowings [line items]
Bonds face amount	$ 250,000
Bonds maturity period	3 years
Secured domestic bonds conversion price | $ / shares	$ 4.8	$ 4.8
Bonds redemption description	(1) if the closing price of AMPI’s ordinary shares on the Taipei Exchange exceeds the conversion price by 30% or more for 30 consecutive business days in the period starting from 3 months after the offering to 40 days before the maturity or (2) the outstanding amount of the bonds falls below 10% of the originally offered in the period aforementioned.
Senior Unsecured International Corporate Bonds [Member]
Disclosure of detailed information about borrowings [line items]
Bonds face amount					$ 1,000
Bonds payable					300,000
Senior Unsecured International Corporate Bonds [Member] | Tranche A [Member]
Disclosure of detailed information about borrowings [line items]
Bonds payable					$ 200,000
Borrowings maturity		3 years
Annual interest rates of bonds		2.15%			2.15%
Senior Unsecured International Corporate Bonds [Member] | Tranche B [Member]
Disclosure of detailed information about borrowings [line items]
Bonds payable					$ 100,000
Borrowings maturity		5 years
Annual interest rates of bonds		2.50%			2.50%

Other Payables - Summary of Oth

Other Payables - Summary of Other Payables (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Subclassifications of assets, liabilities and equities [abstract]
Accrued salary and bonus	$ 12,448,548	$ 443,324	$ 10,384,089
Payables for property, plant and equipment	10,013,971	356,623	14,282,564
Accrued employees' compensation and remuneration to directors	4,405,981	156,908	3,206,036
Accrued employee insurance	1,105,122	39,356	900,367
Accrued utilities	536,491	19,106	504,866
Others	10,905,510	388,373	9,903,768
Other payables	$ 39,415,623	$ 1,403,690	$ 39,181,690

Retirement Benefit Plans - Addi

Retirement Benefit Plans - Additional Information (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021TWD ($)	Dec. 31, 2021USD ($)	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)	Dec. 31, 2020USD ($)
Disclosure of defined benefit plans [line items]
Percentage of monthly pension contributions			6.00%	6.00%	6.00%	6.00%
Pension costs			$ 217,186	$ 7,735	$ 277,041	$ 291,333
Expected contribution to defined benefit plans	$ 513,781	$ 18,297	533,777
Pension plans for executive managers [member]
Disclosure of defined benefit plans [line items]
Pension costs			11,184	$ 398	11,567	$ 11,137
Accrued pension liabilities			$ 346,015		$ 335,109		$ 12,322
Bottom of range [member]
Disclosure of defined benefit plans [line items]
Average duration of the defined benefit obligation			9 years	9 years	10 years
Top of range [member]
Disclosure of defined benefit plans [line items]
Average duration of the defined benefit obligation			16 years	16 years	14 years

Retirement Benefit Plans - Summ

Retirement Benefit Plans - Summary of Defined Benefit Plans Amounts Included in Consolidated Balance Sheets (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018TWD ($)	Dec. 31, 2017TWD ($)
Disclosure of net defined benefit liability (asset) [abstract]
Present value of the defined benefit obligation	$ 12,159,145	$ 433,018	$ 10,668,574
Fair value of the plan assets	(5,962,305)	(212,333)	(5,742,178)
Present value of unfunded defined benefit obligation	6,196,840	220,685	4,926,396	$ 175,442	$ 4,805,016	$ 3,569,265
Recorded under other payables	(102,367)	(3,646)	(19,014)
Recorded under other current assets	26,306	937	11,910
Net defined benefit liability	$ 6,120,779	$ 217,976	$ 4,919,292

Retirement Benefit Plans - Su_2

Retirement Benefit Plans - Summary of Movements in Net Defined Benefit Liability (Asset) (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Disclosure of net defined benefit liability (asset) [line items]
Beginning balance	$ 4,926,396	$ 175,442	$ 4,805,016	$ 3,569,265
Current service cost	193,693	6,898	211,226	224,126
Past service cost and gain on settlements	(25,891)	(922)
Net interest expense (income)	38,200	1,360	54,248	56,070
Recognized in profit or loss	206,002	7,336	265,474	280,196
Return on plan assets (excluding amounts included in net interest)	(109,616)	(3,904)	(104,516)	(16,589)
Changes in financial assumptions	465,433	16,575	398,732	(8,643)
Experience adjustments	281,661	10,031	70,374	302,499
Changes in demographic assumptions	(36,627)	(1,304)	(2,329)	8,190
Changes in other assumptions				22,723
Recognized in other comprehensive income	594,778	21,181	365,262	308,180
Contributions from the employer	(620,433)	(22,095)	(514,617)	(364,237)
Benefits paid from the pension fund	50,707	1,806	0	0
Benefits paid from the Group	(14,520)	(517)	(21,439)	(295,953)
Assets extinguished on settlement	11,910	424
Business combinations	1,018,480	36,270	34,477	1,312,281
Exchange differences on foreign plans	17,447	621	(4,776)	(4,716)
Ending balance	6,196,840	220,685	4,926,396	4,805,016
Defined benefit obligation [member]
Disclosure of net defined benefit liability (asset) [line items]
Beginning balance	10,668,574	379,935	10,297,139	7,910,638
Current service cost	193,693	6,898	211,226	224,126
Past service cost and gain on settlements	(25,891)	(922)
Net interest expense (income)	119,314	4,249	151,635	178,779
Recognized in profit or loss	287,116	10,225	362,861	402,905
Return on plan assets (excluding amounts included in net interest)	0	0	0	0
Changes in financial assumptions	465,433	16,575	398,732	(8,643)
Experience adjustments	281,661	10,031	70,374	302,499
Changes in demographic assumptions	(36,627)	(1,304)	(2,329)	8,190
Changes in other assumptions				22,723
Recognized in other comprehensive income	710,467	25,302	466,777	324,769
Contributions from the employer	0	0	0	0
Benefits paid from the pension fund	(552,430)	(19,673)	(393,897)	(541,989)
Benefits paid from the Group	(14,520)	(517)	(21,439)	(295,953)
Assets extinguished on settlement	0	0
Business combinations	1,018,480	36,270	62,857	2,522,805
Exchange differences on foreign plans	41,458	1,476	(105,724)	(26,036)
Ending balance	12,159,145	433,018	10,668,574	10,297,139
Fair value of plan assets [member]
Disclosure of net defined benefit liability (asset) [line items]
Beginning balance	(5,742,178)	(204,493)	(5,492,123)	(4,341,373)
Current service cost	0	0	0	0
Past service cost and gain on settlements	0
Net interest expense (income)	(81,114)	(2,889)	(97,387)	(122,709)
Recognized in profit or loss	(81,114)	(2,889)	(97,387)	(122,709)
Return on plan assets (excluding amounts included in net interest)	(109,616)	(3,904)	(104,516)	(16,589)
Changes in financial assumptions	0	0	0	0
Experience adjustments	0	0	0	0
Changes in demographic assumptions	0	0	0	0
Changes in other assumptions				0
Recognized in other comprehensive income	(109,616)	(3,904)	(104,516)	(16,589)
Contributions from the employer	(620,433)	(22,095)	(514,617)	(364,237)
Benefits paid from the pension fund	603,137	21,479	393,897	541,989
Benefits paid from the Group	0	0	0	0
Assets extinguished on settlement	11,910	424
Business combinations	0	0	(28,380)	(1,210,524)
Exchange differences on foreign plans	(24,011)	(855)	100,948	21,320
Ending balance	$ (5,962,305)	$ (212,333)	$ (5,742,178)	$ (5,492,123)

Retirement Benefit Plans - Su_3

Retirement Benefit Plans - Summary of Fair Value of the Plan Assets by Major Categories (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Disclosure of fair value of plan assets [abstract]
Cash	$ 2,236,340	$ 79,642	$ 2,396,657
Equity instruments	2,459,708	87,596	2,315,637
Debt instruments	1,092,115	38,893	1,029,884
Others	174,142	6,202	0
Total	$ 5,962,305	$ 212,333	$ 5,742,178

Retirement Benefit Plans - Su_4

Retirement Benefit Plans - Summary of Key Assumptions Used for the Actuarial Valuations (Detail)	Dec. 31, 2020	Dec. 31, 2019
Bottom of range [member]
Disclosure of defined benefit plans [line items]
Discount rates	0.00%	0.08%
Expected rates of salary increase	1.00%	1.00%
Top of range [member]
Disclosure of defined benefit plans [line items]
Discount rates	2.77%	2.85%
Expected rates of salary increase	4.06%	4.01%

Retirement Benefit Plans - Su_5

Retirement Benefit Plans - Summary of Sensitivity Analysis on Defined Obligations (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Actuarial assumption of discount rates [member]
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Change in defined obligation due to increase in actuarial assumption	$ (617,803)	$ (22,002)	$ (555,266)
Change in defined obligation due to decrease in actuarial assumption	600,451	21,384	601,616
Actuarial assumption of expected rates of salary increases [member]
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Change in defined obligation due to increase in actuarial assumption	611,217	21,767	591,915
Change in defined obligation due to decrease in actuarial assumption	$ (565,555)	$ (20,141)	$ (545,528)

Retirement Benefit Plans - Su_6

Retirement Benefit Plans - Summary of Sensitivity Analysis on Defined Obligations (Parenthetical) (Detail)	Dec. 31, 2020
Actuarial assumption of discount rates [member]
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Percentage increase in actuarial assumption	0.50%
Percentage decrease in actuarial assumption	0.50%
Actuarial assumption of expected rates of salary increases [member]
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Percentage increase in actuarial assumption	0.50%
Percentage decrease in actuarial assumption	0.50%

Retirement Benefit Plans - Su_7

Retirement Benefit Plans - Summary of Maturity Analysis of Undiscounted Pension Benefit (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Disclosure of defined benefit plans [line items]
Maturity analysis of undiscounted pension benefit	$ 15,377,190	$ 547,620	$ 14,720,029
Less than 1 year [member]
Disclosure of defined benefit plans [line items]
Maturity analysis of undiscounted pension benefit	498,092	17,738	422,067
1-5 years [member]
Disclosure of defined benefit plans [line items]
Maturity analysis of undiscounted pension benefit	2,553,522	90,937	2,081,540
More than 5 years [member]
Disclosure of defined benefit plans [line items]
Maturity analysis of undiscounted pension benefit	$ 12,325,576	$ 438,945	$ 12,216,422

Equity - Summary of Share Capit

Equity - Summary of Share Capital (Detail) shares in Thousands, $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)shares	Dec. 31, 2020USD ($)shares	Dec. 31, 2019TWD ($)shares
Disclosure of classes of share capital [abstract]
Numbers of shares authorized (in thousands)	5,500,000	5,500,000	5,000,000
Numbers of shares reserved (in thousands) Employee share options	400,000	400,000	400,000
Number of shares issued and fully paid (in thousands)	4,351,592	4,351,592	4,330,528
Share capital authorized	$ 55,000,000	$ 1,958,689	$ 50,000,000
Share capital reserved Employee share options	4,000,000	142,450	4,000,000
Share capital issued and fully paid	$ 43,515,920	$ 1,549,712	$ 43,305,287

Equity - Additional Information

Equity - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2020shares	Dec. 31, 2019shares
Disclosure of classes of share capital [line items]
Number of shares represented by each ADS	2
Percentage of legal reserve on share capital	25.00%
Shares held by subsidiaries	72,941,000	72,941,000
American depository shares (ADs) [member]
Disclosure of classes of share capital [line items]
Number of shares represented by each ADS	2
Number of shares outstanding	107,964,000	125,542,000
Ordinary shares [member]
Disclosure of classes of share capital [line items]
Number of shares outstanding	215,927,000	251,084,000
Top of range [member]
Disclosure of classes of share capital [line items]
Percentage of cash dividend on dividend distribution	30.00%

Equity - Summary of Capital Sur

Equity - Summary of Capital Surplus (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Disclosure of classes of share capital [abstract]
Issuance of ordinary shares	$ 13,548,426	$ 482,494	$ 13,070,330
Merger by share exchange	117,693,658	4,191,369	117,693,658
Difference between consideration and the carrying amount of the subsidiaries' net assets during actual disposal or acquisition	3,240,987	115,420	3,254,489
Capital surplus deficit distributed as cash dividends	134,483,071	4,789,283	134,018,477
Changes in percentage of ownership interest in subsidiaries	1,451	52	891,876
Treasury share transactions	510,449	18,178	364,708
Exercised employee share options	1,617,254	57,595	1,443,995
Expired share options (Notes 22 and 29)	645,903	23,002	645,903
Share of changes in capital surplus of associates	41,239	1,469	16,266
Dividends that the claim period has elapsed and unclaimed by shareholders	3,550	126	1,942
Capital surplus offset deficit	2,819,846	100,422	3,364,690
Employee share options	1,894,952	67,484	1,304,250
Others	569,681	20,288	222,946
Capital surplus for other purpose	2,464,633	87,772	1,527,196
Capital surplus	$ 139,767,550	$ 4,977,477	$ 138,910,363

Equity - Schedule of appropria

Equity - Schedule of appropriation of retained earnings (Detail) - TWD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Appropriation of earnings	$ (8,668,331)	$ 14,310,735	$ 16,559,193
Dividends per share		$ 2	$ 2.5
Legal reserve [member]
Appropriation of earnings	1,697,489	$ 1,697,489	$ 2,203,895
Special reserve [member]
Appropriation of earnings	$ 3,944,915	3,944,915	3,548,844
Cash dividends [member]
Appropriation of earnings		$ 8,668,331	$ 10,806,454

Equity - Summary of Exchange Di

Equity - Summary of Exchange Differences on Translating Foreign Operations (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Balance at January 1	$ 212,802,312		$ 219,027,922
Exchange differences on translating foreign operations	(831,784)	$ (29,622)	(5,202,145)	$ 227,821
Share from associates and joint venture accounted for using the equity method	131,009	4,666	(85,975)	136,608
Balance at December 31	231,731,160	8,252,534	212,802,312	219,027,922
Exchange differences on translating foreign operations [member]
Balance at January 1	(10,762,684)	(383,286)	(5,888,574)	(6,733,659)
Exchange differences on translating foreign operations	(1,173,204)	(41,781)	(4,788,135)	426,186
Share from associates and joint venture accounted for using the equity method	101,038	3,598	(85,975)	136,608
Disposal of associates and joint venture accounted for using the equity method	29,971	1,067		282,291
Disposal of foreign operations	162,940	5,803
Balance at December 31	$ (11,641,939)	$ (414,599)	$ (10,762,684)	$ (5,888,574)

Equity - Summary of Unrealized

Equity - Summary of Unrealized Gain (Loss) on Financial Assets at FVTOCI (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Financial assets at fair value through other comprehensive income [line items]
Balance at January 1	$ 1,770,775
Ending balance	1,741,134	$ 62,006	$ 1,770,775
Unrealized gain (loss) on financial assets at fair value through other comprehensive income [member]
Financial assets at fair value through other comprehensive income [line items]
Balance at January 1	(203,098)	(7,233)	(1,015,107)
Debt instruments	(2,136)	(76)	(2,052)
Equity instruments	(405,020)	(14,424)	(283,472)
Share from associates and joint venture accounted for using the equity method	2,655,570	94,572	1,501,689
Share from the disposal of associates and joint venture accounted for using the equity method	1,094	39
Equity instruments	16,383	583
Share from associates and joint venture accounted for using the equity method	(34,891)	(1,242)	(404,156)
Ending balance	$ 2,027,902	$ 72,219	$ (203,098)

Equity - Schedule Of Detailed I

Equity - Schedule Of Detailed Information About Hedges Of Net Investments Of Foreign Operations (Details) - 12 months ended Dec. 31, 2020 $ in Thousands, $ in Thousands	TWD ($)	USD ($)
Disclosure of detailed information about hedges [line items]
Foreign currency risk – loans denominated in foreign currency	$ (429,265)	$ (15,287)
Balance at December 31	$ (429,265)	$ (15,287)

Equity - Summary of Shares Held

Equity - Summary of Shares Held By Subsidiaries (Detail) shares in Thousands, $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)shares	Dec. 31, 2020USD ($)shares	Dec. 31, 2019TWD ($)shares
Disclosure of subsidiaries [Line Items]
Shares Held By Subsidiaries (in thousands)	72,941	72,941	72,941
Shares Held By Subsidiaries, Value	$ 1,959,107	$ 69,769	$ 1,959,107
ASE Test Limited [member]
Disclosure of subsidiaries [Line Items]
Shares Held By Subsidiaries (in thousands)	44,100	44,100	44,100
Shares Held By Subsidiaries, Value	$ 1,380,721	$ 49,171	$ 1,380,721
J & R Holding Limited [member]
Disclosure of subsidiaries [Line Items]
Shares Held By Subsidiaries (in thousands)	23,352	23,352	23,352
Shares Held By Subsidiaries, Value	$ 381,709	$ 13,594	$ 381,709
ASE Test, Inc. [member]
Disclosure of subsidiaries [Line Items]
Shares Held By Subsidiaries (in thousands)	5,489	5,489	5,489
Shares Held By Subsidiaries, Value	$ 196,677	$ 7,004	$ 196,677
Fair value [member]
Disclosure of subsidiaries [Line Items]
Shares Held By Subsidiaries, Value	5,930,144	211,187	6,068,733
Fair value [member] | ASE Test Limited [member]
Disclosure of subsidiaries [Line Items]
Shares Held By Subsidiaries, Value	3,585,349	127,683	3,669,140
Fair value [member] | J & R Holding Limited [member]
Disclosure of subsidiaries [Line Items]
Shares Held By Subsidiaries, Value	1,898,508	67,611	1,942,876
Fair value [member] | ASE Test, Inc. [member]
Disclosure of subsidiaries [Line Items]
Shares Held By Subsidiaries, Value	$ 446,287	$ 15,893	$ 456,717

Equity - Summary of Non-control

Equity - Summary of Non-controlling Interests (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Balance at January 1	$ 212,802,312		$ 219,027,922
Share of profit for the year	1,681,320	$ 59,876	1,207,974	$ 1,203,588
OTHER COMPREHENSIVE INCOME (LOSS)
Exchange difference on translating foreign operations	(831,784)	(29,622)	(5,202,145)	227,821
Loss from hedging	(429,265)	(15,287)
Balance at December 31	231,731,160	8,252,534	212,802,312	219,027,922
Non-controlling interests [member]
Balance at January 1	13,374,912	476,315	17,639,487	13,195,312
Share of profit for the year	1,681,320	59,876	1,207,974	1,203,588
OTHER COMPREHENSIVE INCOME (LOSS)
Exchange difference on translating foreign operations	178,480	6,356	(414,010)	(198,365)
Unrealized (loss) gain on equity instruments at FVTOCI	1,321	47	(10,773)	(23,928)
Loss from hedging	(145,559)	(5,184)
Remeasurement on defined benefit plans	(9,075)	(323)	(7,422)	(30,079)
Non-controlling interests arising from acquisition or disposal of subsidiaries (Note 29)	(5,658)	(202)	666,651	3,582,866
Subscribing for ordinary shares from subsidiaries' cash capital increase			83,044
Acquisition of non-controlling interests in subsidiaries (Note 31)	(116,738)	(4,157)	(5,084,785)	(2,492,915)
Issuance of new ordinary shares by subsidiaries (Note 29)	1,711,453	60,949
Partial disposal of subsidiaries				1,693,064
Subsidiaries' buy back of their own outstanding ordinary shares (Note 31)	(2,299,533)	(81,892)	(2,017,319)	(801,884)
Non-controlling interest relating to outstanding vested employee share options granted by subsidiaries	1,591,904	56,692	1,672,310	1,936,643
Cash dividends to non-controlling interests	(346,774)	(12,350)	(360,245)	(424,815)
Balance at December 31	$ 15,616,053	$ 556,127	$ 13,374,912	$ 17,639,487

Profit Before Income Tax - Summ

Profit Before Income Tax - Summary of Other Operating Income and Expenses, Net (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Analysis of income and expense [abstract]
Rental income	$ 153,682	$ 5,473	$ 136,301	$ 182,411
Gains (losses) on disposal of property, plant and equipment and other assets	732,796	26,097	(164,187)	(14,644)
Impairment losses on property, plant and equipment	(992,273)	(35,337)	(201,006)	(133,071)
Loss on damages and claims	(176,888)	(6,299)	(459,544)	(24,114)
Others	785,175	27,961	419,881	361,001
Other operating income and expenses, net	$ 502,492	$ 17,895	$ (268,555)	$ 371,583

Profit Before Income Tax - Su_2

Profit Before Income Tax - Summary of Other Income (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Analysis of income and expense [abstract]
Government subsidy	$ 803,049	$ 28,599	$ 624,351	$ 435,950
Interest income	520,783	18,546	549,681	466,211
Dividends income	150,715	5,367	185,061	190,397
Other income	$ 1,474,547	$ 52,512	$ 1,359,093	$ 1,092,558

Profit Before Income Tax - Su_3

Profit Before Income Tax - Summary of Other Gains, Net (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Analysis of income and expense [abstract]
Remeasurement gain on investments accounted for using the equity method due to step acquisition (Note 29)			$ 319,712	$ 7,421,408
Net gains on financial assets mandatorily at FVTPL	$ 3,211,125	$ 114,356	3,631,763	3,388,485
Net gains (losses) arising on financial instruments held for trading	(3,282,973)	(116,915)	(1,984,941)	(1,398,995)
Gain on disposal of subsidiaries (Note 30)	802,753	28,588
Foreign exchange gains (losses), net	1,005,374	35,805	1,125,681	(1,015,615)
Impairment losses on financial assets (Note 14)			(400,201)	(521,010)
Others			(8,025)
Gain on disposal of investments accounted for using the equity method (Note 14)	91,297	3,251
Other gains and losses	$ 1,827,576	$ 65,085	$ 2,683,989	$ 7,874,273

Profit Before Income Tax - Su_4

Profit Before Income Tax - Summary of Finance Costs (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Analysis of income and expense [abstract]
Interest on lease liabilities	$ 88,026	$ 3,135	$ 88,742
Interest on borrowings and bonds payable	3,498,999	124,608	4,211,541	$ 3,597,932
Total interest expense for financial liabilities measured at amortized cost	3,587,025	127,743	4,300,283	3,597,932
Less: Amounts included in the cost of qualifying assets
Inventories related to real estate business	(95,589)	(3,404)	(35,713)	(11,648)
Property, plant and equipment	(54,208)	(1,930)	(77,715)	(50,309)
Investment properties				(89)
Interest expense	3,437,228	122,409	4,186,855	3,535,886
Other finance costs	22,283	793	16,540	32,355
Finance costs	$ 3,459,511	$ 123,202	$ 4,203,395	$ 3,568,241

Profit Before Income Tax - Su_5

Profit Before Income Tax - Summary of Capitalized Borrowing Costs (Detail)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Inventories related to real estate business [member]
Disclosure of detailed information about borrowings [line items]
Annual interest capitalization rates			4.35%
Inventories related to real estate business [member] | Bottom of range [member]
Disclosure of detailed information about borrowings [line items]
Annual interest capitalization rates	4.20%	4.35%
Inventories related to real estate business [member] | Top of range [member]
Disclosure of detailed information about borrowings [line items]
Annual interest capitalization rates	4.75%	4.85%
Property, plant and equipment [member] | Bottom of range [member]
Disclosure of detailed information about borrowings [line items]
Annual interest capitalization rates	0.49%	0.96%	1.84%
Property, plant and equipment [member] | Top of range [member]
Disclosure of detailed information about borrowings [line items]
Annual interest capitalization rates	3.47%	4.03%	4.52%
Investment properties [member] | Bottom of range [member]
Disclosure of detailed information about borrowings [line items]
Annual interest capitalization rates			1.84%
Investment properties [member] | Top of range [member]
Disclosure of detailed information about borrowings [line items]
Annual interest capitalization rates			2.23%

Profit Before Income Tax - Su_6

Profit Before Income Tax - Summary of Depreciation and Amortization (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Analysis of income and expense [Line Items]
Property, plant and equipment depreciation	$ 46,016,548	$ 1,638,766	$ 45,240,667	$ 39,893,786
Right-of-use assets	946,880	33,721	1,055,458
Investment properties	562,260	20,023	594,110	392,667
Intangible assets amortization	3,733,377	132,955	3,576,606	2,402,450
Depreciation and amortization	51,259,065	1,825,465	50,466,841	42,688,903
Depreciation expense	47,525,688	1,692,510	46,890,235	40,286,453
Operating costs [member]
Analysis of income and expense [Line Items]
Intangible assets amortization	2,231,060	79,454	2,092,074	1,394,664
Depreciation expense	44,017,839	1,567,587	43,749,333	37,903,050
Operating expenses [member]
Analysis of income and expense [Line Items]
Intangible assets amortization	1,502,317	53,501	1,484,532	1,007,786
Depreciation expense	$ 3,507,849	$ 124,923	$ 3,140,902	$ 2,383,403

Profit Before Income Tax - Su_7

Profit Before Income Tax - Summary of Operating Expenses Directly Related to Investment Properties (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Direct operating expense from investment property [abstract]
Direct operating expenses of investment properties that generated rental income	$ 1,121,854	$ 39,952	$ 1,232,826	$ 1,276,751

Profit Before Income Tax - Su_8

Profit Before Income Tax - Summary of Employee Benefits Expense (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Post-employment benefits
Defined contribution plans	$ 2,979,167	$ 106,096	$ 3,148,209	$ 2,965,054
Defined benefit plans	217,186	7,735	277,041	291,333
Post-employment benefits	3,196,353	113,831	3,425,250	3,256,387
Equity-settled share-based payments	955,575	34,030	871,699	215,648
Other employee benefits	76,648,412	2,729,644	70,279,752	63,940,430
Employee benefits expense	80,800,340	2,877,505	74,576,701	67,412,465
Operating costs [member]
Post-employment benefits
Employee benefits expense	52,526,164	1,870,590	49,173,778	45,363,170
Operating expense [member]
Post-employment benefits
Employee benefits expense	$ 28,274,176	$ 1,006,915	$ 25,402,923	$ 22,049,295

Profit Before Income Tax - Addi

Profit Before Income Tax - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2019USD ($)
Analysis of income and expense [Line Items]
Percentage of employees' compensation	0.20%	0.20%	0.20%	0.20%
Percentage of remuneration to directors	0.40%	0.40%	0.40%	0.40%
Difference Between Employee Compensation Benefits And Director Remuneration Adjusted In Net Profit	$ 3	$ 100	$ 3	$ 100
Bottom of range [member]
Analysis of income and expense [Line Items]
Percentage of employees' compensation	0.01%	0.01%
Top of range [member]
Analysis of income and expense [Line Items]
Percentage of employees' compensation	1.00%	1.00%
Percentage of remuneration to directors	0.75%	0.75%

Profit Before Income Tax - Su_9

Profit Before Income Tax - Summary of Employees' Compensation and Remuneration to Directors (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Analysis Of Income And Expense [line items]
Employees' compensation	$ 54,909	$ 1,955	$ 34,400
Remuneration to directors	$ 109,818	$ 3,911	68,803
Resolved by the board of directors [member]
Analysis Of Income And Expense [line items]
Employees' compensation			34,400	$ 45,430
Remuneration to directors			68,800	34,070
Recognized in the consolidated financial statements [member]
Analysis Of Income And Expense [line items]
Employees' compensation			34,400	45,430
Remuneration to directors			$ 68,803	$ 34,073

Income Tax - Summary of Major C

Income Tax - Summary of Major Components of Income Tax Expense (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Current income tax
In respect of the current year	$ 6,807,882	$ 242,446	$ 5,002,954	$ 5,207,309
Income tax on unappropriated earnings	680,649	24,240	19,115	(1,022,560)
Changes in estimate for prior years	(472,512)	(16,827)	(352,579)	(103,822)
Current income tax	7,016,019	249,859	4,669,490	4,080,927
Deferred income tax
In respect of the current year	212,338	7,562	563,512	(227,327)
Effect of tax rate changes			54,072	657,346
Changes in estimate for prior years	(103,021)	(3,669)	(213,758)	5,696
Effect of foreign currency exchange differences	(8,438)	(301)	(62,070)	(3,273)
Deferred income tax	100,879	3,592	341,756	432,442
Income tax expense recognized in profit or loss	$ 7,116,898	$ 253,451	$ 5,011,246	$ 4,513,369

Income Tax - Summary of Reconci

Income Tax - Summary of Reconciliation of Income Tax Expense (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Major components of tax expense (income) [abstract]
Profit before income tax	$ 35,768,798	$ 1,273,817	$ 23,279,811	$ 31,937,678
Income tax expense calculated at the statutory rates	16,907,904	602,133	11,802,811	13,540,599
Nontaxable expense in determining taxable income	316,619	11,276	459,133	353,019
Tax-exempt income	(387,212)	(13,790)	(495,883)	(2,515,453)
Additional income tax on unappropriated earnings	680,649	24,240	19,115	(1,022,560)
Loss carry-forward and income tax credits currently used	(1,191,387)	(42,428)	(898,198)	(971,124)
Remeasurement of deferred income tax assets, net	(8,650,569)	(308,069)	(5,588,335)	(4,776,271)
Changes in estimate for prior periods	(472,512)	(16,827)	(352,579)	(103,822)
Unrecognized deductible temporary differences	(138,890)	(4,946)
Withholding tax	52,296	1,862	65,182	8,981
Income tax expense recognized in profit or loss	$ 7,116,898	$ 253,451	$ 5,011,246	$ 4,513,369

Income Tax - Additional Informa

Income Tax - Additional Information (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Disclosure of income taxes [line items]
Taxable temporary differences associated with the investments in subsidiaries for which no deferred tax liabilities recognized	$ 33,474,725	$ 1,192,120	$ 27,139,427
Subsidiaries [member] | China [member]
Disclosure of income taxes [line items]
Reduction tax rate	15.00%

Income Tax - Summary of Income

Income Tax - Summary of Income Tax Recognized Directly in Equity (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Current and deferred tax relating to items charged or credited directly to equity [abstract]
Deferred income tax related to employee share options	$ (1,159)	$ (41)	$ 1,404	$ (1,099)

Income Tax - Summary of Incom_2

Income Tax - Summary of Income Tax Recognized in Other Comprehensive Income (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Income tax relating to components of other comprehensive income [abstract]
Deferred income tax Related to remeasurement of defined benefit plans	$ 114,559	$ 4,080	$ 74,308	$ 55,346
Unrealized loss on equity instruments at fair value through other comprehensive income	(237,460)	(8,457)	(78,124)
Effect of tax rate changes				70,755
Income tax recognized in other comprehensive income	$ (122,901)	$ (4,377)	$ (3,816)	$ 126,101

Income Tax - Summary of Current

Income Tax - Summary of Current Tax Assets and Liabilities (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Current tax assets
Tax refund receivable	$ 303,265	$ 10,800	$ 90,569
Prepaid income tax	399,555	14,229	462,523
Current tax assets	702,820	25,029	553,092
Current tax liabilities
Income tax payable	$ 6,514,502	$ 231,998	$ 4,858,578

Income Tax - Summary of Movemen

Income Tax - Summary of Movements of Deferred Tax Assets and Deferred Tax Liabilities (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Balance at January 1	$ (1,064,533)	$ (37,910)	$ (698,356)	$ (959,666)
Recognized in Profit or Loss	(100,879)	(3,592)	(341,756)	(432,442)
Recognized in Other Comprehensive Income	(122,901)	(4,377)	(3,816)	126,101
Recognized in Equity	(1,159)	(41)	1,404	(1,099)
Exchange Differences	(20,950)	(747)	(62,113)	115,153
Acquisitions Through Business Combinations	533,982	19,016	40,104	550,955
Disposal of Subsidiary	(297,421)	(10,592)
Balance at December 31	(1,073,860)	(38,243)	(1,064,533)	(698,356)
Property, plant and equipment [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Balance at January 1	(4,661,773)	(166,018)	(4,546,314)	(3,879,066)
Recognized in Profit or Loss	(422,833)	(15,058)	(80,593)	(600,229)
Exchange Differences	43,364	1,544	(17,949)	(21,146)
Acquisitions Through Business Combinations	21,875	779	(16,917)	(45,873)
Disposal of Subsidiary	(13,982)	(498)
Balance at December 31	(5,033,349)	(179,251)	(4,661,773)	(4,546,314)
Defined benefit obligation [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Balance at January 1	1,078,583	38,411	1,064,824	780,240
Recognized in Profit or Loss	(36,633)	(1,305)	(57,746)	(131,687)
Recognized in Other Comprehensive Income	114,559	4,080	74,308	126,101
Exchange Differences	1,005	36	(2,803)	27,884
Acquisitions Through Business Combinations	212,941	7,583		262,286
Balance at December 31	1,370,455	48,805	1,078,583	1,064,824
Mandatorily at fair value through profit or loss [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Balance at January 1	250,315	8,914	207,021	(104,903)
Recognized in Profit or Loss	(135,103)	(4,811)	43,285	284,659
Exchange Differences	(74)	(3)	9	(137)
Acquisitions Through Business Combinations	2,085	74		27,402
Disposal of Subsidiary	(11,281)	(402)
Balance at December 31	105,942	3,772	250,315	207,021
Other temporary differences [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Balance at January 1	1,188,521	42,328	1,272,672	1,028,409
Recognized in Profit or Loss	624,442	22,238	6,148	(26,147)
Recognized in Other Comprehensive Income	(237,460)	(8,457)	(78,124)
Recognized in Equity	(1,159)	(41)	1,404	(1,099)
Exchange Differences	(42,771)	(1,523)	(21,763)	74,327
Acquisitions Through Business Combinations	114,036	4,061	8,184	294,540
Disposal of Subsidiary	(119,564)	(4,258)
Balance at December 31	1,526,045	54,348	1,188,521	1,272,672
Temporary differences [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Balance at January 1	(2,144,354)	(76,365)	(2,001,797)	(2,175,320)
Recognized in Profit or Loss	29,873	1,064	(88,906)	(473,404)
Recognized in Other Comprehensive Income	(122,901)	(4,377)	(3,816)	126,101
Recognized in Equity	(1,159)	(41)	1,404	(1,099)
Exchange Differences	1,524	54	(42,506)	80,928
Acquisitions Through Business Combinations	350,937	12,497	(8,733)	538,355
Disposal of Subsidiary	(144,827)	(5,158)
Balance at December 31	(2,030,907)	(72,326)	(2,144,354)	(2,001,797)
Unused tax losses [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Balance at January 1	542,781	19,330	672,275	681,441
Recognized in Profit or Loss	(44,651)	(1,590)	(166,128)	(50,059)
Exchange Differences	(915)	(33)	(12,203)	28,293
Acquisitions Through Business Combinations	183,045	6,519	48,837	12,600
Disposal of Subsidiary	(152,594)	(5,434)
Balance at December 31	527,666	18,792	542,781	672,275
Unused tax credits [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Balance at January 1	537,040	19,125	631,166	534,213
Recognized in Profit or Loss	(86,100)	(3,066)	(86,722)	91,021
Exchange Differences	(21,559)	(768)	(7,404)	5,932
Balance at December 31	429,381	$ 15,291	$ 537,040	631,166
Adjustments arising from initial application [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Recognized in Profit or Loss	$ (100,878)			(97,358)
Adjustments arising from initial application [member] | Other temporary differences [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Recognized in Profit or Loss				(97,358)
Adjustments arising from initial application [member] | Temporary differences [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Recognized in Profit or Loss				$ (97,358)

Income Tax - Summary of Unrecog

Income Tax - Summary of Unrecognized Deferred Tax Assets Related to Loss Carry-forward, Investment Credits and Deductible Temporary Differences (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Disclosure of temporary difference, unused tax losses and unused tax credits [abstract]
Loss carry-forward	$ 1,497,056	$ 53,314	$ 966,783
Investment credits	49,611	1,767	51,217
Deductible temporary differences	377,242	13,434	446,754
Unrecognized deferred tax assets	$ 1,923,909	$ 68,515	$ 1,464,754

Income Tax - Summary of Unused

Income Tax - Summary of Unused Loss Carry-forward (Detail) - Dec. 31, 2020 - Unused tax losses [member] $ in Thousands, $ in Thousands	TWD ($)	USD ($)
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Unused loss carry-forward	$ 2,024,722	$ 72,106
2021 [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Unused loss carry-forward	79,849	2,844
2022 [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Unused loss carry-forward	140,029	4,987
2023 [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Unused loss carry-forward	192,607	6,859
2024 [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Unused loss carry-forward	172,337	6,137
2025 and thereafter [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Unused loss carry-forward	$ 1,439,900	$ 51,279

Income Tax - Summary of Unuse_2

Income Tax - Summary of Unused Investment Credits (Detail) - 12 months ended Dec. 31, 2020 $ in Thousands, $ in Thousands	TWD ($)	USD ($)
Unused tax credits [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Remaining Creditable Amount	$ 478,992	$ 17,058
Purchase of machinery and equipment [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Expiry Year	2027
Purchase of machinery and equipment [member] | Unused tax credits [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Remaining Creditable Amount	$ 405,188	14,430
Others [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Expiry Year	2026 and thereafter
Others [member] | Unused tax credits [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Remaining Creditable Amount	$ 73,804	$ 2,628

Income Tax - Summary of Project

Income Tax - Summary of Projects were Exempted From Income Tax (Detail) - Construction and expansion of 2009 [member] - ASE Test, Inc. [member]	12 Months Ended
	Dec. 31, 2020
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Tax-exemption period, start date	2018-01
Tax-exemption period, end date	2022-12

Earnings Per Share - Summary of

Earnings Per Share - Summary of Earnings and Weighted Average Number of Ordinary Shares Outstanding in Computation of Earnings Per Share (Detail) shares in Thousands, $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)shares	Dec. 31, 2020USD ($)shares	Dec. 31, 2019TWD ($)shares	Dec. 31, 2018TWD ($)shares
Earnings per share [line items]
Profit for the year attributable to owners of the Company	$ 26,970,580	$ 960,490	$ 17,060,591	$ 26,220,721
Effect of potentially dilutive ordinary shares:
Employee share options issued by subsidiaries	(521,073)	(18,557)	(385,865)	(418,295)
Earnings used in the computation of diluted earnings per share	$ 26,449,507	$ 941,933	$ 16,674,726	$ 25,802,426
Weighted average number of ordinary shares in the computation of basic earnings per share	4,265,732	4,265,732	4,251,964	4,245,247
Effect of potentially dilutive ordinary shares:
From employee share options	22,086	22,086	10,232	5,103
From employees' compensation	815	815	570	779
Weighted average number of ordinary shares in computation of diluted earnings per share	4,288,633	4,288,633	4,262,766	4,251,129

Earnings Per Share - Additional

Earnings Per Share - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2020
Earnings per share [line items]
Number of shares represented by each ADS	2

Share-based Payment Arrangeme_3

Share-based Payment Arrangements - Additional Information (Detail) $ / shares in Units, $ / shares in Units, $ in Thousands, $ in Thousands	1 Months Ended		4 Months Ended	8 Months Ended		12 Months Ended
	Sep. 30, 2020shares	Nov. 30, 2019shares	Apr. 29, 2018$ / shares	Dec. 31, 2018TWD ($)shares	Dec. 31, 2018TWD ($)$ / shares	Dec. 31, 2020TWD ($)shares$ / shares	Dec. 31, 2020USD ($)shares$ / shares	Dec. 31, 2019TWD ($)shares$ / shares	Dec. 31, 2018TWD ($)	Dec. 31, 2020USD ($)
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Compensation cost of employee share options						$ 955,575	$ 34,030	$ 871,699	$ 215,648
USIE option plans [member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Capital surplus decreased				$ 1,239,456	$ 1,239,456	1,120,111		981,078	$ 1,239,456	$ 39,890
USISH option plans [member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Capital surplus decreased						$ 1,010,219		$ 105,785		$ 35,976
Options granted						1,140,000	1,140,000	17,167,000
Number of equity instruments other than options granted						672,000	672,000	6,156,000
USISH option plans [member] | Share Option [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Options granted		17,167,000
USISH option plans [member] | Bottom of range [member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Valid term of share option plans		3.0 years
USISH option plans [member] | Weighted average [member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Valid term of share option plans		4.0 years
USISH option plans [member] | Top of range [member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Valid term of share option plans		5.0 years
ASE Inc. option plans [member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Share option to purchase of ordinary shares						0.5	0.5
Weighted average exercise price of share options | $ / shares			$ 41
The Company Option Plans [member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Valid term of share option plans						10 years	10 years
Percentage of cash dividend per ordinary share exceeds market price						1.50%	1.50%
Weighted average exercise price of share options | (per share)					$ 68.5	$ 68.5	$ 2.4	$ 69.3
Options granted				131,863,000
USISH core employees stock ownership plan [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Options granted		6,156,000
Share based compensation number of additional shares to be granted		6,403,000
USISH core employees stock ownership plan [Member] | Phase One [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Valid term of share option plans		4.5 years
USISH core employees stock ownership plan [Member] | Phase Two [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Valid term of share option plans		3.5 years
USISH core employees stock ownership plan [Member] | Phase Three [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Valid term of share option plans		2.5 years
USISH second share option plan [member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Number of shares granted	1,140,000
USISH second share option plan [member] | Phase One [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Valid term of share option plans	1.2 years
USISH second share option plan [member] | Phase Two [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Valid term of share option plans	2.2 years
USISH second share option plan [member] | Phase Three [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Valid term of share option plans	3.2 years
USISH second share option plan [member] | Bottom of range [member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Valid term of share option plans	2.2 years
USISH second share option plan [member] | Weighted average [member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Valid term of share option plans	3.2 years
USISH second share option plan [member] | Top of range [member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Valid term of share option plans	4.2 years
USISH restricted share plan [member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Valid term of share option plans	2 years
Number of equity instruments other than options granted	425,000
Period of lock in of ordinary shares to be issued upon satisfaction of performance conditions	1 year 3 months 18 days

Share-based Payment Arrangeme_4

Share-based Payment Arrangements - Summary of Information About ASE Inc. Option Plans (Detail)	4 Months Ended		8 Months Ended	12 Months Ended
	Apr. 29, 2018TWD ($)shares$ / shares	Apr. 29, 2018$ / shares	Dec. 31, 2018TWD ($)shares$ / shares	Dec. 31, 2020shares$ / shares	Dec. 31, 2020shares$ / shares$ / shares	Dec. 31, 2019shares$ / shares	Dec. 31, 2018shares$ / shares
ASE Inc. option plans [member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Number of options, beginning balance	135,961,000						135,961,000
Number of options, transferred to the Company in accordance with the joint share exchange agreement	(113,712,000)
Number of options, forfeited	(1,692,000)
Number of options, exercised	(20,557,000)
Number of options, Ending balance	0
Weighted average exercise price, Beginning balance | $ / shares	$ 30.2						$ 30.2
Transferred from ASE | $	$ 30.9
Weighted average exercise price, Options forfeited | $ / shares	$ 36.3
Weighted average exercise price, Options exercised | $ / shares	$ 26
Weighted average exercise price, Ending balance | $ / shares		$ 0
The Company Option Plans [member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Number of options, beginning balance				170,786,000	170,786,000	183,814,000
Number of options, transferred to the Company in accordance with the joint share exchange agreement			56,856,000
Options granted			131,863,000
Number of options, forfeited			(1,582,000)	(3,949,000)	(3,949,000)	(4,214,000)
Number of options, expired				(1,006,000)	(1,006,000)
Number of options, exercised			(3,323,000)	(21,064,000)	(21,064,000)	(8,814,000)
Number of options, Ending balance			183,814,000	144,767,000	144,767,000	170,786,000	183,814,000
Number of options, exercisable, end of year			36,354,000	67,388,000	67,388,000	33,822,000	36,354,000
Weighted average exercise price, Beginning balance | $ / shares				$ 57		$ 58.1
Transferred from ASE | $			$ 61.7
Options granted | $ / shares			$ 56.4
Weighted average exercise price, Options expired | $ / shares					$ 40.8
Weighted average exercise price, Options forfeited | $ / shares			71.5	58		61.8
Weighted average exercise price, Options exercised | $ / shares			43.6	49.2		48.4
Weighted average exercise price, Ending balance | $ / shares			58.1	56.9		57	$ 58.1
Weighted average exercise price, Options exercisable, end of year | $ / shares			$ 58.1	$ 61.4	$ 61.4	$ 63.5	$ 58.1
The Company Option Plans [member] | Bottom of range [member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Fair value of options granted (NT$)			16,280				16,280
The Company Option Plans [member] | Top of range [member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Fair value of options granted (NT$)			19,120				19,120

Share-based Payment Arrangeme_5

Share-based Payment Arrangements - Summary of ASE Inc. Option Plans Outstanding Share Options (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
ASE Inc. option plans [member] | Fourth share options exercise price [member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Range of Exercise Price Per Share	$ 45.2
Weighted Average Remaining Contractual Life (Years)	3 months 18 days	6 months
ASE Inc. option plans [member] | Fifth share options exercise price [member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Range of Exercise Price Per Share	$ 73	$ 73
Weighted Average Remaining Contractual Life (Years)	4 years 8 months 12 days	5 years 8 months 12 days
ASE Inc. option plans [member] | Bottom of range [member] | Fourth share options exercise price [member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Range of Exercise Price Per Share		$ 40.8
ASE Inc. option plans [member] | Top of range [member] | Fourth share options exercise price [member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Range of Exercise Price Per Share		45.2
The Company Option Plans [member] | First share options exercise price [member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Range of Exercise Price Per Share	$ 52.9	$ 54.4
Weighted Average Remaining Contractual Life (Years)	7 years 10 months 24 days	8 years 10 months 24 days

Share-based Payment Arrangeme_6

Share-based Payment Arrangements - Summary of Information About USIE Option Plans (Detail) - USIE option plans [member] shares in Thousands	12 Months Ended
	Dec. 31, 2020shares$ / shares	Dec. 31, 2019shares$ / shares	Dec. 31, 2018shares$ / shares
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Number of options, beginning balance | shares	8,349	16,711	25,556
Number of options, forfeited | shares	(7)
Number of options, exercised | shares	(8,342)	(8,362)	(8,845)
Number of options, Ending balance | shares		8,349	16,711
Number of options, exercisable, end of year | shares		8,349	16,711
Weighted average exercise price, Beginning balance | $ / shares	$ 2.3	$ 2.1	$ 2.2
Weighted average exercise price, Options exercised | $ / shares	2.3	2	2.2
Weighted average exercise price, Options forfeited | $ / shares	$ 2.9
Weighted average exercise price, Ending balance | $ / shares		2.3	2.1
Weighted average exercise price, Options exercisable, end of year | $ / shares		$ 2.3	$ 2.1

Share-based Payment Arrangeme_7

Share-based Payment Arrangements - Summary of USIE Option Plans Outstanding Share Options (Detail) - USIE option plans [member]	12 Months Ended
	Dec. 31, 2019$ / shares
First share options exercise price [member]
Disclosure of range of exercise prices of outstanding share options [Line Items]
Range of Exercise Price Per Share	$ 1.5
Weighted Average Remaining Contractual Life (Years)	1 year
Third share options exercise price [member]
Disclosure of range of exercise prices of outstanding share options [Line Items]
Range of Exercise Price Per Share	$ 2.9
Weighted Average Remaining Contractual Life (Years)	1 year 4 months 24 days

Share-based Payment Arrangeme_8

Share-based Payment Arrangements - Summary of Information About USISH Option Plans (Detail) - USISH option plans [member]	12 Months Ended
	Dec. 31, 2020shares¥ / shares	Dec. 31, 2019shares¥ / shares	Dec. 31, 2018shares¥ / shares
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Number of options, beginning balance	35,077,000	21,537,000	22,341,000
Number of options, granted	1,140,000	17,167,000
Number of options, forfeited	(636,000)	(463,000)	(804,000)
Number of options, exercised	(4,315,000)	(3,164,000)
Number of options, Ending balance	31,266,000	35,077,000	21,537,000
Number of options, exercisable, end of year	13,416,000	13,694,000	12,884,000
Weighted average exercise price, Beginning balance | ¥ / shares	¥ 14.5	¥ 15.5	¥ 15.5
Weighted average exercise price options granted | ¥ / shares	21.7	13.3
Weighted average exercise price, Options forfeited | ¥ / shares	14	15.4	15.5
Weighted average exercise price options exercised | ¥ / shares	15.5	15.5
Weighted average exercise price, Ending balance | ¥ / shares	14.6	14.5	15.5
Weighted average exercise price, Options exercisable, end of year | ¥ / shares	¥ 15.5	¥ 15.5	¥ 15.5
Bottom of range [member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Fair value of options granted (CNY)	7.03	6.27
Top of range [member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Fair value of options granted (CNY)	8.93	8.35

Share-based Payment Arrangeme_9

Share-based Payment Arrangements - Summary of USISH's outstanding share options balance sheet (Detail) - USISH Option Plans [member] - ¥ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share options [Member]
Disclosure of range of exercise prices of outstanding share options [Line Items]
Range of Exercise Price Per Share	¥ 15.5	¥ 15.5
Weighted average remaining contractual life of outstanding share options	4 years 10 months 24 days	5 years 10 months 24 days
Stock option plans [Member]
Disclosure of range of exercise prices of outstanding share options [Line Items]
Range of Exercise Price Per Share	¥ 13.3	¥ 13.3
Weighted average remaining contractual life of outstanding share options	3 years 10 months 24 days	4 years 10 months 24 days
2020 Share Options [Member]
Disclosure of range of exercise prices of outstanding share options [Line Items]
Range of Exercise Price Per Share	¥ 21.7
Weighted average remaining contractual life of outstanding share options	3 years 10 months 24 days

Share-based Payment Arrangem_10

Share-based Payment Arrangements - Summary of Information About Restricted Shares (Detail)	12 Months Ended
	Dec. 31, 2020shares¥ / shares	Dec. 31, 2019shares¥ / shares
Disclosure of terms and conditions of share-based payment arrangement [line items]
Options exercisable, end of year
Exercise Price Per Share, Options exercisable, end of year | ¥ / shares
USISH option plans [member]
Disclosure of terms and conditions of share-based payment arrangement [line items]
Balance at January  1	6,156,000
Options granted	672,000	6,156,000
Options exercised	(1,281,000)
Balance at December  31	5,547,000	6,156,000
Fair value of options granted (RMB)	18.55	13.47
Exercise Price Per Share, Begining | ¥ / shares	¥ 13.3
Exercise Price Per Share, Options granted | ¥ / shares	4.9	¥ 13.3
Exercise Price Per Share, Options exercised | ¥ / shares	13.2
Exercise Price Per Share, Ending | ¥ / shares	¥ 12.2	¥ 13.3

Share-based Payment Arrangem_11

Share-based Payment Arrangements - Summary of Outstanding Restricted Shares At Balance Sheet (Detail) - USISH option plans [member]	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
2019 restricted shares [Member]
Dislcosure of Range Exercise Prices of Outstanding Restricted Shares [Line Items]
Range of Exercise Price Per Share	13.2	13.3
Remaining Contractual Life (Years)	3 years 3 months 18 days	4 years 3 months 18 days
2020 restricted shares [Member]
Dislcosure of Range Exercise Prices of Outstanding Restricted Shares [Line Items]
Remaining Contractual Life (Years)	1 year 8 months 12 days

Share-based Payment Arrangem_12

Share-based Payment Arrangements - Summary of Fair Value using Trinomial Tree Model and Inputs (Detail)	12 Months Ended
	Dec. 31, 2020Years¥ / shares	Dec. 31, 2019Years¥ / shares
Trinomial Tree Model [member] | USISH stock option plan [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Share price at the grant date		¥ 15.84
Exercise price		13.34
Trinomial Tree Model [member] | USISH two thousand and twenty share options plan [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Share price at the grant date	¥ 21.55
Exercise price	21.65
Binomial Method [Member] | USISH core employees stock ownership plan restricted shares amended in 2020 [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Share price at the grant date		16.60
Exercise price		¥ 13.34
Expected volatility		57.21%
Lock-up periods | Years		1
Risk free interest rate		1.55%
Binomial Method [Member] | USISH core employees stock ownership plan [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Share price at the grant date		¥ 16.30
Exercise price		¥ 13.34
Expected volatility		47.77%
Lock-up periods | Years		1
Risk free interest rate		2.70%
Binomial Method [Member] | USISH employee stock ownership restricted stock ownership plan amendment 2020 [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Share price at the grant date	¥ 24.30
Expected volatility	56.97%
Lock-up periods | Years	1.3
Risk free interest rate	2.63%
Bottom of range [member] | Trinomial Tree Model [member] | USISH stock option plan [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Expected volatility		45.07%
Expected lives | Years		3
Risk free interest rate		2.80%
Bottom of range [member] | Trinomial Tree Model [member] | USISH two thousand and twenty share options plan [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Expected volatility	48.14%
Expected lives | Years	2.2
Risk free interest rate	2.80%
Top of range [member] | Trinomial Tree Model [member] | USISH stock option plan [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Expected volatility		51.80%
Expected lives | Years		5
Risk free interest rate		2.97%
Top of range [member] | Trinomial Tree Model [member] | USISH two thousand and twenty share options plan [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Expected volatility	53.57%
Expected lives | Years	4.2
Risk free interest rate	2.99%

Business Combinations - Summary

Business Combinations - Summary of Subsidiary Acquired (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)
AMPI [member]
Disclosure of detailed information about business combination [Line Items]
Principal Activity	Engaged in the manufacturing of integrated circuit
Date of Acquisition	Apr. 30, 2019
Proportion of Voting Equity Interests Acquired	50.97%	50.97%
Cash Consideration	$ 250,000
ASEEE [member]
Disclosure of detailed information about business combination [Line Items]
Principal Activity	Engaged in the production of embedded substrate
Date of Acquisition	Apr. 26, 2019
Proportion of Voting Equity Interests Acquired	51.00%	51.00%
USIPL [member]
Disclosure of detailed information about business combination [Line Items]
Principal Activity	Engaged in the design and manufacturing of electronic components and new electronic applications
Date of Acquisition	Oct. 31, 2019
Proportion of Voting Equity Interests Acquired	60.00%	60.00%
Cash Consideration	$ 313,057
FAFG [member]
Disclosure of detailed information about business combination [Line Items]
Principal Activity	Holding company and the group engaged in the design and manufacturing of electronic components
Date of Acquisition	Dec. 1, 2020
Proportion of Voting Equity Interests Acquired	100.00%	100.00%
Cash Consideration	$ 12,829,372	$ 456,887
SPIL [member]
Disclosure of detailed information about business combination [Line Items]
Principal Activity	Engaged in the assembly, testing and turnkey services of integrated circuits
Date of Acquisition	Apr. 30, 2018
Proportion of Voting Equity Interests Acquired	100.00%	100.00%
Cash Consideration	$ 168,440,585

Business Combinations - Additio

Business Combinations - Additional Information (Detail) $ in Thousands, $ in Thousands	1 Months Ended			12 Months Ended
	Jul. 31, 2019USD ($)	Apr. 30, 2019TWD ($)shares	Apr. 30, 2019USD ($)shares	Dec. 31, 2020TWD ($)shares	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Disclosure of subsidiaries [Line Items]
Significant unobservable inputs discount rate				31.00%	31.00%
Revenue from continuing operations				$ 497,146,285	$ 17,704,640	$ 413,782,708	$ 397,261,461
Profit from continuing operations				$ 29,707,746	$ 1,057,968	$ 18,030,506	25,687,447
Call option on the remaining non-controlling interests				40.00%	40.00%
Gain recognized from remeasuring fair value of equity interest before business combination		$ 243,057
Top of range [member]
Disclosure of subsidiaries [Line Items]
Contingent consideration recognised as of acquisition date				$ 42,805
USIFR [Member]
Disclosure of subsidiaries [Line Items]
Consideration paid in cash for shares				10,800,558
ArrangementForContingentConsiderationByMakingDepositTo TrustFund				$ 294,244
UGPL [Member]
Disclosure of subsidiaries [Line Items]
Number of shares issued | shares				25,940
FAFG [Member]
Disclosure of subsidiaries [Line Items]
Percentage of shareholdings acquired by subsidiary				100.00%
Percentage of Ownership (%)				100.00%	100.00%
ASE Embedded Electronics Inc [member]
Disclosure of subsidiaries [Line Items]
Consideration paid in cash for shares		1,500,000
Gain recognized from remeasuring fair value of equity interest before business combination		76,655
Accumulated deficits compensated by capital reduction		1,147,595,000
Ordinary shares acquired		$ 150,000	$ 150,000
Percentage of Ownership (%)	100.00%
ASE Embedded Electronics Inc [member] | TDK Corporation [Member]
Disclosure of subsidiaries [Line Items]
Ordinary shares acquired	$ 6,000
ASE Test, Inc. [member]
Disclosure of subsidiaries [Line Items]
Percentage of ownership interest in joint venture		50.97%	50.97%
ASE Test, Inc. [member] | Private Placement [Member]
Disclosure of subsidiaries [Line Items]
Shares subscribed | shares		100,000	100,000
Consideration paid in cash for shares		$ 250,000
Siliconware Precision Industries Co., Ltd. [member]
Disclosure of subsidiaries [Line Items]
Significant unobservable inputs discount rate				25.00%	25.00%
Gain recognized from remeasuring fair value of equity interest before business combination							$ 7,421,408
UGPL [Member]
Disclosure of subsidiaries [Line Items]
Percentage of shareholdings acquired by subsidiary				60.00%

Business Combinations - Summa_2

Business Combinations - Summary of Consideration Transferred in business combination (Detail) - Dec. 31, 2020 $ in Thousands, $ in Thousands	TWD ($)	USD ($)
SPIL [member]
Disclosure of detailed information about business combination [line items]
Fair value of identifiable net assets acquired	$ 132,033,220
SPIL [member] | Consideration transferred [member]
Disclosure of detailed information about business combination [line items]
Cash	168,440,585
Fair value of identifiable net assets acquired	168,440,585
AMPI [member]
Disclosure of detailed information about business combination [line items]
Fair value of identifiable net assets acquired	849,863
AMPI [member] | Consideration transferred [member]
Disclosure of detailed information about business combination [line items]
Cash	250,000
Fair value of identifiable net assets acquired	250,000
ASEEE [member] | Consideration transferred [member]
Disclosure of detailed information about business combination [line items]
Cash
Equity instrument issued
Contingent consideration arrangement
Fair value of identifiable net assets acquired
USIPL [member]
Disclosure of detailed information about business combination [line items]
Fair value of identifiable net assets acquired	331,192
USIPL [member] | Consideration transferred [member]
Disclosure of detailed information about business combination [line items]
Cash	313,057
Fair value of identifiable net assets acquired	313,057
FAFG [member]
Disclosure of detailed information about business combination [line items]
Fair value of identifiable net assets acquired	8,198,468	$ 291,968
FAFG [member] | Consideration transferred [member]
Disclosure of detailed information about business combination [line items]
Cash	10,800,558	384,635
Equity instrument issued	1,734,570	61,772
Contingent consideration arrangement	294,244	10,479
Fair value of identifiable net assets acquired	$ 12,829,372	$ 456,886

Business Combinations - Summa_3

Business Combinations - Summary of Assets Acquired and Liabilities Assumed at the Date of Acquisition (Detail) - Dec. 31, 2020 $ in Thousands, $ in Thousands	TWD ($)	USD ($)
SPIL [member]
Disclosure of detailed information about business combination [Line Items]
Cash and cash equivalents	$ 20,088,970
Trade and other receivables	15,840,649
Inventories	5,693,644
Property, plant and equipment	81,985,622
Intangible assets	31,354,386
Others	24,945,922
Trade and other payables	(19,755,598)
Borrowings and bonds payables	(24,157,174)
Others	(3,963,201)
Fair value of identifiable net assets acquired	132,033,220
AMPI [member]
Disclosure of detailed information about business combination [Line Items]
Cash and cash equivalents	349,496
Trade and other receivables	371,144
Inventories	403,887
Property, plant and equipment	683,207
Intangible assets	128,900
Others	237,766
Trade and other payables	(224,295)
Borrowings and bonds payables	(951,519)
Others	(148,723)
Fair value of identifiable net assets acquired	849,863
ASEEE [member]
Disclosure of detailed information about business combination [Line Items]
Cash and cash equivalents	23,197
Trade and other receivables	5,732
Inventories	11,033
Property, plant and equipment	1,361,572
Intangible assets	290,757
Others	317,888
Trade and other payables	(133,278)
Borrowings and bonds payables	(1,371,395)
Others	(290,273)
Fair value of identifiable net assets acquired	215,233
USIPL [member]
Disclosure of detailed information about business combination [Line Items]
Cash and cash equivalents	108,718
Trade and other receivables	58,713
Inventories	229
Property, plant and equipment	525,048
Intangible assets	11,704
Others	99,112
Trade and other payables	(217,887)
Borrowings and bonds payables	(190,737)
Others	(63,708)
Fair value of identifiable net assets acquired	331,192
FAFG [member]
Disclosure of detailed information about business combination [Line Items]
Cash and cash equivalents	2,349,164	$ 83,660
Trade and other receivables	4,434,296	157,917
Inventories	4,763,237	169,631
Property, plant and equipment	1,730,783	61,637
Intangible assets	642,838	22,893
Others	1,798,564	64,051
Trade and other payables	(4,575,720)	(162,953)
Borrowings and bonds payables	(356,417)	(12,693)
Others	(2,588,277)	(92,175)
Fair value of identifiable net assets acquired	$ 8,198,468	$ 291,968

Business Combinations - Summa_4

Business Combinations - Summary of Goodwill Recognized on Acquisitions (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018TWD ($)	Dec. 31, 2017TWD ($)
Disclosure of detailed information about business combination [Line Items]
Ending balance of goodwill in respective year	$ 54,777,439	$ 1,950,764	$ 50,198,436	$ 1,787,693	$ 49,974,446	$ 9,934,494
SPIL [member]
Disclosure of detailed information about business combination [Line Items]
Total consideration	168,440,585
Add: Non-controlling interests	3,582,866
Less: Fair value of identifiable net assets acquired	(132,033,220)
Ending balance of goodwill in respective year	39,990,231
AMPI [member]
Disclosure of detailed information about business combination [Line Items]
Total consideration	250,000
Add: Fair value of investments previously owned	315,925
Add: Non-controlling interests	416,716
Less: Fair value of identifiable net assets acquired	(849,863)
Ending balance of goodwill in respective year	132,778
ASEEE [member]
Disclosure of detailed information about business combination [Line Items]
Add: Fair value of investments previously owned	117,609
Add: Non-controlling interests	105,464
Less: Fair value of identifiable net assets acquired	(215,233)
Ending balance of goodwill in respective year	7,840
USIPL [member]
Disclosure of detailed information about business combination [Line Items]
Total consideration	313,057
Add: Non-controlling interests	142,494
Less: Fair value of identifiable net assets acquired	(331,192)
Ending balance of goodwill in respective year	124,359
FAFG [member]
Disclosure of detailed information about business combination [Line Items]
Total consideration	12,829,372	456,887
Add: Non-controlling interests	(5,635)	(201)
Less: Fair value of identifiable net assets acquired	(8,198,468)	(291,968)
Ending balance of goodwill in respective year	$ 4,625,269	$ 164,718

Business Combinations - Summa_5

Business Combinations - Summary of Net Cash Outflow (Inflow) on Acquisition of Subsidiary (Detail) - 12 months ended Dec. 31, 2020 $ in Thousands, $ in Thousands	TWD ($)	USD ($)	USD ($)
SPIL [member]
Disclosure of detailed information about business combination [Line Items]
Total consideration	$ 168,440,585
Less: Payable for consideration representing the ordinary shares originally held by ASE	(53,109,760)
Less: Cash and cash equivalent acquired	(20,088,970)
Net cash outflow (inflow) on acquisition of subsidiaries	95,241,855
AMPI [member]
Disclosure of detailed information about business combination [Line Items]
Total consideration	250,000
Less: Cash and cash equivalent acquired	(349,496)
Net cash outflow (inflow) on acquisition of subsidiaries	(99,496)
ASEEE [member]
Disclosure of detailed information about business combination [Line Items]
Less: Cash and cash equivalent acquired	(23,197)
Net cash outflow (inflow) on acquisition of subsidiaries	(23,197)
USIPL [member]
Disclosure of detailed information about business combination [Line Items]
Total consideration	313,057
Less: Cash and cash equivalent acquired	(108,718)
Net cash outflow (inflow) on acquisition of subsidiaries	204,339
FAFG [member]
Disclosure of detailed information about business combination [Line Items]
Total consideration	12,829,372		$ 456,887
Less: Cash and cash equivalent acquired	(2,349,164)	$ (83,660)
Net cash outflow (inflow) on acquisition of subsidiaries	$ 8,745,638	$ 311,454

Business Combinations - Summa_6

Business Combinations - Summary of Impact of Acquisitions by Comprehensive Income (Detail) $ in Thousands, $ in Thousands	2 Months Ended	8 Months Ended			12 Months Ended
	Dec. 31, 2019TWD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)
SPIL [member]
Disclosure of detailed information about business combination [Line Items]
Net Profit (loss)				$ 7,627,382
SPIL [member] | Increase (decrease) due to changes in accounting policy [member]
Disclosure of detailed information about business combination [Line Items]
Operating revenue				$ 61,247,727
AMPI [member]
Disclosure of detailed information about business combination [Line Items]
Net Profit (loss)			$ (217,163)
AMPI [member] | Increase (decrease) due to changes in accounting policy [member]
Disclosure of detailed information about business combination [Line Items]
Operating revenue			$ 704,243
ASEEE [member]
Disclosure of detailed information about business combination [Line Items]
Net Profit (loss)		$ (469,598)
ASEEE [member] | Increase (decrease) due to changes in accounting policy [member]
Disclosure of detailed information about business combination [Line Items]
Operating revenue		$ (1,159)
FAFG [member]
Disclosure of detailed information about business combination [Line Items]
Net Profit (loss)					$ 91,179	$ 3,247
FAFG [member] | Increase (decrease) due to changes in accounting policy [member]
Disclosure of detailed information about business combination [Line Items]
Operating revenue					$ 2,043,440	$ 72,772
USIPL [member]
Disclosure of detailed information about business combination [Line Items]
Net Profit (loss)	$ (11,995)
USIPL [member] | Increase (decrease) due to changes in accounting policy [member]
Disclosure of detailed information about business combination [Line Items]
Operating revenue	$ 39,080

Disposal of Subsidiaries - Summ

Disposal of Subsidiaries - Summary of Analysis of Assets and Liabilities on Date Control was Lost (Detail) - 12 months ended Dec. 31, 2020 - SPL Cayman Holdings Limited [member] $ in Thousands, $ in Thousands	TWD ($)	USD ($)
Current assets
Cash and cash equivalents	$ 200,347	$ 7,135
Trade receivables, net	318,425	11,340
Inventories	239,865	8,542
Other current assets	111,913	3,985
Non-Current Assets
Property, plant and equipment	7,546,413	268,747
Right-of-use assets	812,861	28,948
Deferred tax assets	298,217	10,620
Other non-current assets	43,482	1,548
Current Liabilities
Trade and other payables	(1,739,330)	(61,942)
Current portion of long-term borrowings	(1,746,000)	(62,179)
Other current liabilities	(24,564)	(875)
Non-Current Liabilities
Long-term borrowings	(2,947,682)	(104,974)
Deferred tax liabilities	(796)	(28)
Net assets disposed of	$ 3,113,151	$ 110,867

Disposal of Subsidiaries - Su_2

Disposal of Subsidiaries - Summary of Gain on Disposal of Subsidiaries (Detail) - 12 months ended Dec. 31, 2020 - SPL Cayman Holdings Limited [member] $ in Thousands, $ in Thousands	TWD ($)	USD ($)
Disclosure of gain from disposals of subsidiaries [line items]
Total consideration	$ 4,078,844	$ 145,258
Net assets disposed of	(3,113,151)	(110,867)
Reclassification of accumulated exchange difference from equity to profit or loss due to the loss of control over SF	(162,940)	(5,803)
Gain on disposal of SF	$ 802,753	$ 28,588

Disposal of Subsidiaries - Su_3

Disposal of Subsidiaries - Summary of Net Cash Inflow on Disposal of Susbsidiaries (Detail) - 12 months ended Dec. 31, 2020 - SPL Cayman Holdings Limited [member] $ in Thousands, $ in Thousands	TWD ($)	USD ($)
Disclosure Of Net Cash Inflow On Disposal Of Subsidiaries [Line Items]
Consideration received in cash and cash equivalents	$ 4,078,844	$ 145,258
Less: Cash and cash equivalent balances disposed of	(200,347)	(7,135)
Other receivables (the outstanding receivables of consideration, net of relevant expenditure)	(161,458)	(5,750)
Net cash inflow on disposals of subsidiaries	$ 3,717,039	$ 132,373

Disposal of Subsidiaries - Addi

Disposal of Subsidiaries - Additional Information (Detail) - Shenzhen Hiwin System Limited [Member] ¥ in Thousands	12 Months Ended
	Dec. 31, 2020CNY (¥)
Disposal of Subsidiaries [Line Items]
Percentage of Ownership (%)	100.00%
Total consideration	¥ 966,000

Equity Transaction with Non-c_2

Equity Transaction with Non-controlling Interests - Additional Information (Detail) $ / shares in Units, $ / shares in Units, $ in Thousands, $ in Thousands	May 31, 2020USD ($)	Sep. 30, 2020$ / shares	Jul. 31, 2019USD ($)$ / shares	Jul. 31, 2018TWD ($)$ / shares	Dec. 31, 2019TWD ($)shares	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Sep. 01, 2020TWD ($)shares	Sep. 01, 2020USD ($)shares	Jul. 31, 2019TWD ($)	Jul. 01, 2019TWD ($)shares	Jul. 31, 2018USD ($)
USI Enterprise Limited [member]
Increase (decrease) in capital surplus						$ 2,760,175	$ 98,297	$ 780,533	$ 27,797		$ (1,625,448)
Number of shares approved for repurchase | shares								10,308,000	10,308,000		7,378,000
Shares repurchase price per share | $ / shares		$ 19.47	$ 14.30
USI Enterprise Limited [member] | Bottom of range [member]
Percentage of increase in shareholdings		95.00%	95.42%
USI Enterprise Limited [member] | Top of range [member]
Percentage of increase in shareholdings		99.62%	98.72%
ASEN [member]
Increase (decrease) in capital surplus										$ (2,650,950)
Amount of shares transferred												$ 97,748
Percentage of shareholdings			30.00%
Amount of shareholdings			$ 162,870
ASEN [member] | Bottom of range [member]
Percentage of increase in ownership			70.00%
ASEN [member] | Top of range [member]
Percentage of increase in ownership			100.00%
USI INC [member]
Increase (decrease) in capital surplus				$ 142
Ordinary shares outstanding acquired price | $ / shares				$ 18
USISH [Member]
Number of shares repurchased | shares					13,037
Increase (decrease) in capital surplus					$ 334,719
USISH [Member] | Bottom of range [member]
Percentage of increase in shareholdings					74.60%
USISH [Member] | Top of range [member]
Percentage of increase in shareholdings					77.70%
ASEEE [member]
Increase (decrease) in capital surplus											$ 128,805
Percentage of ShareHolding Held			100.00%
USIPL [Member]
Increase (decrease) in capital surplus						$ 13,502	$ 481
Amount of shareholdings	$ 24,500
Percentage of shareholdings	40.00%
USIPL [Member] | Bottom of range [member]
Percentage of increase in ownership	60.00%
USIPL [Member] | Top of range [member]
Percentage of increase in ownership	100.00%

Cash Flows Information - Summar

Cash Flows Information - Summary of Non-cash Investing Activities (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Payments for property, plant and equipment
Purchase of property, plant and equipment	$ 59,024,201	$ 2,102,001	$ 63,073,887	$ 39,092,238
Increase in other non-current assets	78,291	2,788	68,560	402,255
Decrease (increase) in other payables	3,029,162	107,876	(6,254,579)	1,942,259
Capitalized borrowing costs	(54,208)	(1,930)	(77,715)	(50,309)
Payments for property, plant and equipment	62,077,446	2,210,735	56,810,153	41,386,443
Proceeds from disposal of property, plant and equipment
Consideration from disposal of property, plant and equipment	5,184,925	184,648	441,444	1,133,435
Decrease (increase) in other receivables	(735,812)	(26,204)	7,495	(5,791)
Proceeds from disposal of property, plant and equipment	4,449,113	158,444	448,939	1,127,644
Payments for investment properties
Purchase of investment properties			2,532	125,853
Capitalized borrowing costs				(89)
Proceeds from disposals of investment property	6,352	226	2,532	125,764
Payments for other intangible assets
Purchase of other intangible assets	982,655	34,995	1,350,908	537,659
Decrease in other payables			60,160	40,106
Purchase of intangible assets classified as investing activities	$ 982,655	$ 34,995	$ 1,411,068	$ 577,765

Cash Flows Information - Change

Cash Flows Information - Change in Liabilities Arising From Financing Activities (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Disclosure Of Non Cash Investing Activities [line items]
Beginning balance	$ 223,982,006	$ 7,976,569	$ 198,147,734	$ 76,511,879
Beginning balance			208,132,097
Net financing cash flows	(9,129,670)	(325,131)	15,104,066	101,653,172
Interest under operating activities	111	4	1,766
Rent expense under operating activities	(7,729)	(275)
Lease liabilities	584,642	20,821	536,216
Non-cash changes
Acquisition of subsidiaries (Note 29)	990,023	35,257	2,508,101	24,157,174
Bonds conversion				(4,457,191)
Reclassification for the application of IFRS 9				(1,301,994)
Amortization of issuance cost	171,232	6,098	200,673	216,973
Disposal of subsidiaries (Note 30)	(4,694,352)	(167,178)
Effects of foreign currency exchange	(2,530,260)	(90,110)	(2,261,592)	1,367,721
Adjustments for government subsidy	41,650	1,483
Lease modifications	(289,687)	(10,316)	(239,321)
Ending balance	209,117,966	7,447,222	223,982,006	198,147,734
Short-term borrowings [member]
Disclosure Of Non Cash Investing Activities [line items]
Beginning balance	40,572,329	1,444,883	43,263,469	17,962,471
Beginning balance			47,163,103
Net financing cash flows	(1,502,323)	(53,502)	(4,683,142)	22,327,813
Reclassification of foreign currency borrowings which lift to hedge foreign currency equity instruments	(3,850,000)	(137,108)	(1,499,000)
Non-cash changes
Acquisition of subsidiaries (Note 29)	356,417	12,693	656,820	3,619,858
Reclassification for the application of IFRS 9				(1,301,994)
Effects of foreign currency exchange	(978,565)	(34,849)	(1,065,452)	655,321
Ending balance	34,597,858	1,232,117	40,572,329	43,263,469
Bonds payable [member]
Disclosure Of Non Cash Investing Activities [line items]
Beginning balance	36,522,155	1,300,647	16,985,936	23,142,780
Beginning balance			16,985,936
Net financing cash flows	19,717,149	702,178	19,279,033	(6,185,600)
Non-cash changes
Acquisition of subsidiaries (Note 29)			245,664	4,457,191
Bonds conversion				(4,457,191)
Amortization of issuance cost	14,250	507	11,522	28,756
Ending balance	56,253,554	2,003,332	36,522,155	16,985,936
Long-term borrowings [member]
Disclosure Of Non Cash Investing Activities [line items]
Beginning balance	141,078,598	5,024,168	137,898,329	35,406,628
Beginning balance			137,898,329
Net financing cash flows	(26,500,139)	(943,737)	1,144,731	85,510,959
Reclassification of foreign currency borrowings which lift to hedge foreign currency equity instruments	3,850,000	137,108	1,499,000
Non-cash changes
Acquisition of subsidiaries (Note 29)			1,523,968	16,080,125
Amortization of issuance cost	156,982	5,591	189,151	188,217
Disposal of subsidiaries (Note 30)	(4,693,682)	(167,154)
Effects of foreign currency exchange	(1,542,685)	(54,939)	(1,176,581)	712,400
Adjustments for government subsidy	41,650	1,483
Ending balance	112,390,724	4,002,520	141,078,598	$ 137,898,329
Lease liabilities [member]
Disclosure Of Non Cash Investing Activities [line items]
Beginning balance	5,808,924	206,871
Beginning balance			6,084,729
Net financing cash flows	(844,357)	(30,070)	(636,556)
Interest under operating activities	111	4	1,766
Rent expense under operating activities	(7,729)	(275)
Lease liabilities	584,642	20,821	536,216
Non-cash changes
Acquisition of subsidiaries (Note 29)	633,606	22,564	81,649
Disposal of subsidiaries (Note 30)	(670)	(24)
Effects of foreign currency exchange	(9,010)	(322)	(19,559)
Lease modifications	(289,687)	(10,316)	(239,321)
Ending balance	$ 5,875,830	$ 209,253	$ 5,808,924

Financial Instruments - Summary

Financial Instruments - Summary of Fair Value of Financial Instruments Not Measured at Fair Value but for Which Fair Value is Disclosed (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Disclosure of detailed information about financial instruments [line items]
Bonds payable	$ 56,253,554	$ 2,003,332	$ 36,522,155
Fair value [member]
Disclosure of detailed information about financial instruments [line items]
Bonds payable	$ 56,448,769	$ 2,010,284	$ 36,766,117

Financial Instruments - Summa_2

Financial Instruments - Summary of Fair Value of Financial Instruments that are Measured at Fair Value on a Recurring Basis (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Disclosure of detailed information about financial instruments [line items]
Financial assets mandatorily classified as at FVTPL	$ 6,135,793	$ 218,511	$ 5,288,996
Financial assets at FVTOCI	2,367,547	84,314	3,800,465
Financial liabilities at FVTPL	1,537,208	54,744	973,571
Investments in equity instruments designated at fair value through other comprehensive income	728,398	25,940	755,903
Trade receivables, net	1,012,736	36,066	1,014,872
Swap contracts [member] | Derivative financial instruments [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets mandatorily classified as at FVTPL	99,312	3,537	56,561
Financial liabilities at FVTPL	1,448,972	51,602	862,581
Forward Exchange Contract [member] | Derivative financial instruments [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets mandatorily classified as at FVTPL	122,511	4,363	104,308
Financial liabilities at FVTPL	9,020	321	110,990
Quoted ordinary shares [member] | Non derivative financial assets [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets mandatorily classified as at FVTPL	4,064,438	144,745	3,460,123
Open-end mutual funds [member] | Non derivative financial assets [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets mandatorily classified as at FVTPL	339,338	12,085	662,290
Unquoted preferred shares [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets at FVTOCI, Investments in equity instruments	151,329	5,389	158,718
Unquoted preferred shares [member] | Non derivative financial assets [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets mandatorily classified as at FVTPL	385,440	13,726	377,440
Private-placement funds [member] | Non derivative financial assets [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets mandatorily classified as at FVTPL	1,124,754	40,055	603,718
Unquoted ordinary shares [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets at FVTOCI, Investments in equity instruments	567,377	20,206	565,028
Limited partnership [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets at FVTOCI, Investments in equity instruments	9,692	345	32,157
Unsecured subordinate corporate bonds [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets at FVTOCI, Investments in debt instruments	1,012,736	36,066	1,014,872
Trade receivables, net	626,413	22,308	2,029,690
Forward exchange contracts [member] | Derivative financial instruments [member]
Disclosure of detailed information about financial instruments [line items]
Financial liabilities at FVTPL	9,020	321	110,990
Call options [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets mandatorily classified as at FVTPL			24,556
Call options [member] | Derivative financial instruments [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets mandatorily classified as at FVTPL			24,556
Target redemption forward contracts [member] | Derivative financial instruments [member]
Disclosure of detailed information about financial instruments [line items]
Financial liabilities at FVTPL	79,216	2,821
Level 1 of fair value hierarchy [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets mandatorily classified as at FVTPL	4,403,776	156,830	4,122,413
Financial assets at FVTOCI	0	0
Trade receivables, net	0	0
Level 1 of fair value hierarchy [member] | Swap contracts [member] | Derivative financial instruments [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets mandatorily classified as at FVTPL	0	0
Financial liabilities at FVTPL	0	0
Level 1 of fair value hierarchy [member] | Forward Exchange Contract [member] | Derivative financial instruments [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets mandatorily classified as at FVTPL	0	0
Financial liabilities at FVTPL	0	0
Level 1 of fair value hierarchy [member] | Quoted ordinary shares [member] | Non derivative financial assets [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets mandatorily classified as at FVTPL	4,064,438	144,745	3,460,123
Level 1 of fair value hierarchy [member] | Open-end mutual funds [member] | Non derivative financial assets [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets mandatorily classified as at FVTPL	339,338	12,085	662,290
Level 1 of fair value hierarchy [member] | Unquoted preferred shares [member]
Disclosure of detailed information about financial instruments [line items]
Investments in equity instruments designated at fair value through other comprehensive income	0	0
Level 1 of fair value hierarchy [member] | Unquoted preferred shares [member] | Non derivative financial assets [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets mandatorily classified as at FVTPL	0	0
Level 1 of fair value hierarchy [member] | Private-placement funds [member] | Non derivative financial assets [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets mandatorily classified as at FVTPL	0	0
Level 1 of fair value hierarchy [member] | Unquoted ordinary shares [member]
Disclosure of detailed information about financial instruments [line items]
Investments in equity instruments designated at fair value through other comprehensive income	0	0
Level 1 of fair value hierarchy [member] | Limited partnership [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets at FVTOCI, Investments in equity instruments	0	0
Level 1 of fair value hierarchy [member] | Unsecured subordinate corporate bonds [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets at FVTOCI, Investments in debt instruments	0	0
Trade receivables, net	0	0
Level 1 of fair value hierarchy [member] | Target redemption forward contracts [member] | Derivative financial instruments [member]
Disclosure of detailed information about financial instruments [line items]
Financial liabilities at FVTPL	0	0
Level 2 of fair value hierarchy [Member]
Disclosure of detailed information about financial instruments [line items]
Financial assets mandatorily classified as at FVTPL	221,823	7,900	160,869
Financial assets at FVTOCI	0	0
Financial liabilities at FVTPL	1,537,208	54,744	973,571
Level 2 of fair value hierarchy [Member] | Swap contracts [member] | Derivative financial instruments [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets mandatorily classified as at FVTPL	99,312	3,537	56,561
Financial liabilities at FVTPL	1,448,972	51,602	862,581
Level 2 of fair value hierarchy [Member] | Forward Exchange Contract [member] | Derivative financial instruments [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets mandatorily classified as at FVTPL	122,511	4,363	104,308
Level 2 of fair value hierarchy [Member] | Quoted ordinary shares [member] | Non derivative financial assets [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets mandatorily classified as at FVTPL	0	0
Level 2 of fair value hierarchy [Member] | Open-end mutual funds [member] | Non derivative financial assets [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets mandatorily classified as at FVTPL	0	0
Level 2 of fair value hierarchy [Member] | Unquoted preferred shares [member]
Disclosure of detailed information about financial instruments [line items]
Investments in equity instruments designated at fair value through other comprehensive income	0	0
Level 2 of fair value hierarchy [Member] | Unquoted preferred shares [member] | Non derivative financial assets [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets mandatorily classified as at FVTPL	0	0
Level 2 of fair value hierarchy [Member] | Private-placement funds [member] | Non derivative financial assets [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets mandatorily classified as at FVTPL	0	0
Level 2 of fair value hierarchy [Member] | Unquoted ordinary shares [member]
Disclosure of detailed information about financial instruments [line items]
Investments in equity instruments designated at fair value through other comprehensive income	0	0
Level 2 of fair value hierarchy [Member] | Limited partnership [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets at FVTOCI, Investments in equity instruments	0	0
Level 2 of fair value hierarchy [Member] | Unsecured subordinate corporate bonds [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets at FVTOCI, Investments in debt instruments	0	0
Trade receivables, net	0	0
Level 2 of fair value hierarchy [Member] | Forward exchange contracts [member] | Derivative financial instruments [member]
Disclosure of detailed information about financial instruments [line items]
Financial liabilities at FVTPL	9,020	321	110,990
Level 2 of fair value hierarchy [Member] | Target redemption forward contracts [member] | Derivative financial instruments [member]
Disclosure of detailed information about financial instruments [line items]
Financial liabilities at FVTPL	79,216	2,821
Level 3 of fair value hierarchy [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets mandatorily classified as at FVTPL	1,510,194	53,781	1,005,714
Financial assets at FVTOCI	2,367,547	84,314	3,800,465
Trade receivables, net	0	0
Level 3 of fair value hierarchy [member] | Swap contracts [member] | Derivative financial instruments [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets mandatorily classified as at FVTPL	0	0
Financial liabilities at FVTPL	0	0
Level 3 of fair value hierarchy [member] | Forward Exchange Contract [member] | Derivative financial instruments [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets mandatorily classified as at FVTPL	0	0
Financial liabilities at FVTPL	0	0
Level 3 of fair value hierarchy [member] | Quoted ordinary shares [member] | Non derivative financial assets [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets mandatorily classified as at FVTPL	0	0
Level 3 of fair value hierarchy [member] | Open-end mutual funds [member] | Non derivative financial assets [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets mandatorily classified as at FVTPL	0	0
Level 3 of fair value hierarchy [member] | Unquoted preferred shares [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets at FVTOCI, Investments in equity instruments	151,329	5,389	158,718
Level 3 of fair value hierarchy [member] | Unquoted preferred shares [member] | Non derivative financial assets [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets mandatorily classified as at FVTPL	385,440	13,726	377,440
Level 3 of fair value hierarchy [member] | Private-placement funds [member] | Non derivative financial assets [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets mandatorily classified as at FVTPL	1,124,754	40,055	603,718
Level 3 of fair value hierarchy [member] | Unquoted ordinary shares [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets at FVTOCI, Investments in equity instruments	567,377	20,206	565,028
Level 3 of fair value hierarchy [member] | Limited partnership [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets at FVTOCI, Investments in equity instruments	9,692	345	32,157
Level 3 of fair value hierarchy [member] | Unsecured subordinate corporate bonds [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets at FVTOCI, Investments in debt instruments	1,012,736	36,066	1,014,872
Trade receivables, net	626,413	22,308	2,029,690
Level 3 of fair value hierarchy [member] | Call options [member] | Derivative financial instruments [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets mandatorily classified as at FVTPL			$ 24,556
Level 3 of fair value hierarchy [member] | Target redemption forward contracts [member] | Derivative financial instruments [member]
Disclosure of detailed information about financial instruments [line items]
Financial liabilities at FVTPL	$ 0	$ 0

Financial Instruments - Additio

Financial Instruments - Additional Information (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)	Dec. 31, 2020USD ($)
Disclosure of detailed information about financial instruments [line items]
Significant unobservable inputs discount rate	31.00%	31.00%
Increase percentage of significant unobservable inputs discount rate	1.00%	1.00%	0.10%
Fair value of unquoted shares decreased	$ 9,700		$ 7,200		$ 345
Fair value of bonds decreased	$ 5,000	$ 178	$ 6,000
Percentage of trade receivables	27.00%		37.00%		27.00%
Call options [member]
Disclosure of detailed information about financial instruments [line items]
Significant unobservable inputs discount rate			20.00%
At fair value [member] | Call options [member]
Disclosure of detailed information about financial instruments [line items]
Increase percentage of significant unobservable inputs discount rate			1.00%
Fair value of bonds decreased			$ 855
Bottom of range [member] | Actuarial assumption of discount rates [member]
Disclosure of detailed information about financial instruments [line items]
Significant unobservable inputs discount rate	10.00%	10.00%
Top of range [member] | Actuarial assumption of discount rates [member]
Disclosure of detailed information about financial instruments [line items]
Significant unobservable inputs discount rate	30.00%	30.00%
Floating interest rate [member]
Disclosure of detailed information about financial instruments [line items]
Increase decrease in profit before tax	$ 862,000	$ 30,698	1,232,000	$ 1,398,000
Currency risk [member]
Disclosure of detailed information about financial instruments [line items]
Value at risk	35,000		82,000	129,000	$ 1,246
Other price risk [member]
Disclosure of detailed information about financial instruments [line items]
Increase decrease in profit before tax	59,000	2,101	51,000	$ 64,000
Equity debt ratio				1.00%
Increase decrease in other comprehensive income	$ 7,000	$ 249	$ 8,000	$ 16,000

Financial Instruments - Summa_3

Financial Instruments - Summary of Financial Assets Measured at Level 3 Fair Value (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Disclosure of fair value measurement of assets [line items]
Beginning Balance	$ 557,223,706
Net increase in trade receivables	(9,396,304)	$ (334,626)	$ 995,839	$ (9,313,539)
Exercise of call option	(1,934,530)	(68,894)	(1,149,227)	(1,269,680)
Ending Balance	583,576,894	20,782,653	557,223,706
Available-for-sale [member] | Level 3 of fair value hierarchy [member]
Disclosure of fair value measurement of assets [line items]
Beginning Balance	4,806,179	171,160	2,072,446
Recognized in profit or loss	(17,941)	(639)	3,431
Recognized in other comprehensive income (included in unrealized losses on financial assets at FVTOCI)	(151,992)	(5,413)	(218,173)
Recognized in other comprehensive income (effects of foreign currency exchange)	(31,017)	(1,105)	(20,063)
Net increase in trade receivables	6,005,816	213,883	3,171,205
Trade receivables factoring (purchases)	(7,409,093)	(263,857)	(1,141,515)
Purchases	1,152,402	41,040	951,513
Disposals	(450,625)	(16,048)	(12,665)
Exercise of call option	(25,988)	(926)
Ending Balance	3,877,741	138,095	4,806,179	2,072,446
Available-for-sale [member] | Level 3 of fair value hierarchy [member] | FVTPL equity instrument [member]
Disclosure of fair value measurement of assets [line items]
Beginning Balance	1,005,714	35,816	475,123
Recognized in profit or loss	(17,941)	(639)	3,431
Recognized in other comprehensive income (included in unrealized losses on financial assets at FVTOCI)	0
Recognized in other comprehensive income (effects of foreign currency exchange)	(15,455)	(550)	(14,368)
Net increase in trade receivables	0
Trade receivables factoring (purchases)	0
Purchases	893,234	31,810	541,528
Disposals	(329,370)	(11,730)
Exercise of call option	(25,988)	(926)
Ending Balance	1,510,194	53,781	1,005,714	475,123
Available-for-sale [member] | Level 3 of fair value hierarchy [member] | FVOCI equity instruments [member]
Disclosure of fair value measurement of assets [line items]
Beginning Balance	755,903	26,920	580,399
Recognized in profit or loss	0
Recognized in other comprehensive income (included in unrealized losses on financial assets at FVTOCI)	(149,856)	(5,337)	(216,121)
Recognized in other comprehensive income (effects of foreign currency exchange)	(15,562)	(555)	(5,695)
Net increase in trade receivables	0
Trade receivables factoring (purchases)	0
Purchases	259,168	9,230	409,985
Disposals	(121,255)	(4,318)	(12,665)
Ending Balance	728,398	25,940	755,903	580,399
Available-for-sale [member] | Level 3 of fair value hierarchy [member] | FVOCI debt instruments [member]
Disclosure of fair value measurement of assets [line items]
Beginning Balance	3,044,562	108,424	1,016,924
Recognized in profit or loss	0
Recognized in other comprehensive income (included in unrealized losses on financial assets at FVTOCI)	(2,136)	(76)	(2,052)
Recognized in other comprehensive income (effects of foreign currency exchange)	0
Net increase in trade receivables	5,635,706	200,702	3,171,205
Trade receivables factoring (purchases)	(7,038,983)	(250,676)	(1,141,515)
Purchases	0
Disposals	0
Ending Balance	1,639,149	58,374	$ 3,044,562	$ 1,016,924
Available-for-sale [member] | Level 3 of fair value hierarchy [member] | FVTPL debt instrument [member]
Disclosure of fair value measurement of assets [line items]
Net increase in trade receivables	370,110	13,181
Trade receivables factoring (purchases)	$ (370,110)	$ (13,181)

Financial Instruments - Summa_4

Financial Instruments - Summary of Categories of Financial Instruments (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Disclosure of detailed information about financial instruments [line items]
Mandatorily at FVTPL	$ 6,135,793	$ 218,511	$ 5,288,996
Measured at amortized cost (Note 1)	147,521,583	5,253,618	139,668,804
Trade receivables, net	91,833,989	3,270,441	78,948,473
Held for trading	1,537,208	54,744	973,571
Financial liabilities for hedging	11,188,244	398,442	3,233,301
Measured at amortized cost (Note 2)	304,737,749	10,852,485	310,187,110
Financial assets at fair value through other comprehensive income, category [member]
Disclosure of detailed information about financial instruments [line items]
Equity instruments	728,398	25,940	755,903
Debt instruments	1,012,736	36,066	1,014,872
Trade receivables, net	$ 626,413	$ 22,308	$ 2,029,690

Financial Instruments - Summa_5

Financial Instruments - Summary of Detailed Information About Hedges (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Disclosure of detailed information about hedges [line items]
Financial liabilities for hedging – current	$ 5,277,325	$ 187,939	$ 3,233,301
Fair value hedge of borrowings denominated in foreign currencies [member]
Disclosure of detailed information about hedges [line items]
Financial liabilities for hedging – current	3,307,018	117,771	$ 3,233,301
Current Financial Assets For Hedging – current	0
Hedges of net investment in foreign operations [member]
Disclosure of detailed information about hedges [line items]
Financial liabilities for hedging – current	1,970,307	70,168
Financial liabilities for hedging – non-current	5,910,919	210,503
Current Financial Assets For Hedging – current	0
Non Current Financial Assets For Hedging – non-current	$ 0	$ 0

Financial Instruments - Summa_6

Financial Instruments - Summary of Detailed Information About Hedges Items (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2020USD ($)
Borrowings denominated in foreign currencies [member]
Disclosure of detailed information about hedged items [line items]
Change in Value Used for Calculating Hedge Ineffectiveness, Hedging Instrument			$ 71,743
Hedged item, assets	$ 2,859,132		2,791,574	$ 101,821
Accumulated Amount of Fair Value Hedge Adjustments on Hedged Item, Asset			15,625
Fair value hedge of borrowings denominated in foreign currencies [member]
Disclosure of detailed information about hedged items [line items]
Change in Value Used for Calculating Hedge Ineffectiveness, Hedging Instrument	157,842	$ 5,621
Hedged item, assets	(157,842)			(5,621)
Accumulated Amount of Fair Value Hedge Adjustments on Hedged Item, Asset	(142,217)			(5,065)
Hedges of net investment in foreign operations [member]
Disclosure of detailed information about hedged items [line items]
Change in Value Used for Calculating Hedge Ineffectiveness, Hedging Instrument	574,824	$ 20,471
Hedged item, assets	(574,824)		$ (71,743)	(20,471)
Accumulated Gains or Losses in Other Equity, Continuing Hedges	$ (574,824)			$ (20,471)

Financial Instruments - Summa_7

Financial Instruments - Summary of Interest Rate Risk (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Fair value interest rate risk [member]
Disclosure of detailed information about financial instruments [line items]
Financial liabilities	$ 56,599,417	$ 2,015,649	$ 41,952,056
Cash flow interest rate risk [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets	45,489,788	1,620,007	46,467,663
Financial liabilities	$ 131,715,366	$ 4,690,718	$ 169,709,237

Financial Instruments - Summa_8

Financial Instruments - Summary of Maturity Analysis for Non-derivative Financial Liabilities (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Less than 1 month [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Non-derivative financial liabilities undiscounted amounts	$ 68,903,001	$ 2,453,810	$ 52,919,574
Less than 1 month [member] | Obligation under leases [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Non-derivative financial liabilities undiscounted amounts	103,734	3,694	75,388
Less than 1 month [member] | Non interest bearing [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Non-derivative financial liabilities undiscounted amounts	43,111,390	1,535,306	35,283,757
Less than 1 month [member] | Floating interest rate [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Non-derivative financial liabilities undiscounted amounts	13,792,596	491,189	10,740,844
Less than 1 month [member] | Fixed interest rate [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Non-derivative financial liabilities undiscounted amounts	11,895,281	423,621	6,819,585
1 to 3 months [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Non-derivative financial liabilities undiscounted amounts	52,992,946	1,887,213	49,340,483
1 to 3 months [member] | Obligation under leases [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Non-derivative financial liabilities undiscounted amounts	151,921	5,410	115,297
1 to 3 months [member] | Non interest bearing [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Non-derivative financial liabilities undiscounted amounts	44,122,659	1,571,320	38,803,904
1 to 3 months [member] | Floating interest rate [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Non-derivative financial liabilities undiscounted amounts	8,190,076	291,669	6,708,303
1 to 3 months [member] | Fixed interest rate [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Non-derivative financial liabilities undiscounted amounts	528,290	18,814	3,712,979
3 months to 1 year [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Non-derivative financial liabilities undiscounted amounts	22,407,360	797,983	29,672,377
3 months to 1 year [member] | Obligation under leases [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Non-derivative financial liabilities undiscounted amounts	619,908	22,077	532,747
3 months to 1 year [member] | Non interest bearing [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Non-derivative financial liabilities undiscounted amounts	8,223,684	292,866	7,989,256
3 months to 1 year [member] | Floating interest rate [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Non-derivative financial liabilities undiscounted amounts	10,214,154	363,752	18,868,999
3 months to 1 year [member] | Fixed interest rate [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Non-derivative financial liabilities undiscounted amounts	3,349,614	119,288	2,281,375
1-5 years [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Non-derivative financial liabilities undiscounted amounts	151,252,482	5,386,485	169,317,078
1-5 years [member] | Obligation under leases [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Non-derivative financial liabilities undiscounted amounts	1,779,041	63,356	1,536,600
1-5 years [member] | Non interest bearing [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Non-derivative financial liabilities undiscounted amounts	319,510	11,379	33,797
1-5 years [member] | Floating interest rate [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Non-derivative financial liabilities undiscounted amounts	102,253,481	3,641,506	133,341,087
1-5 years [member] | Fixed interest rate [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Non-derivative financial liabilities undiscounted amounts	46,900,450	1,670,244	34,405,594
More than 5 years [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Non-derivative financial liabilities undiscounted amounts	17,895,489	637,304	15,477,307
More than 5 years [member] | Obligation under leases [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Non-derivative financial liabilities undiscounted amounts	4,088,301	145,595	4,412,859
More than 5 years [member] | Non interest bearing [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Non-derivative financial liabilities undiscounted amounts	176,536	6,287	184,338
More than 5 years [member] | Floating interest rate [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Non-derivative financial liabilities undiscounted amounts	7,999,130	284,869	7,190,891
More than 5 years [member] | Fixed interest rate [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Non-derivative financial liabilities undiscounted amounts	$ 5,631,522	$ 200,553	$ 3,689,219

Financial Instruments - Summa_9

Financial Instruments - Summary of Detailed Information about Maturity Analysis of Obligation under Leases (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Less than 1 year [member] | Obligation under leases [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Non-derivative financial liabilities undiscounted amounts	$ 875,563	$ 31,181	$ 723,432
1-5 years [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Non-derivative financial liabilities undiscounted amounts	151,252,482	5,386,485	169,317,078
1-5 years [member] | Obligation under leases [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Non-derivative financial liabilities undiscounted amounts	1,779,041	63,356	1,536,600
5 to 10 Years [member] | Obligation under leases [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Non-derivative financial liabilities undiscounted amounts	1,422,331	50,653	1,454,128
10 to 15 Years [member] | Obligation under leases [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Non-derivative financial liabilities undiscounted amounts	776,735	27,661	856,825
15 to 20 Years [member] | Obligation under leases [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Non-derivative financial liabilities undiscounted amounts	674,446	24,019	712,696
More than 20 Years [member] | Obligation under leases [member]
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Non-derivative financial liabilities undiscounted amounts	$ 1,214,789	$ 43,262	$ 1,389,210

Financial Instruments - Summ_10

Financial Instruments - Summary of Maturity Analysis for Derivative Financial Instruments (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Less than 1 month [member]
Disclosure of maturity analysis for derivative financial liabilities [line items]
Net settled		$ 1,087
Gross settled	$ (150,128)	(5,346)	$ 71,041
Less than 1 month [member] | Forward exchange contracts [member]
Disclosure of maturity analysis for derivative financial liabilities [line items]
Net settled	30,514		(74,864)
Gross settled	64,444	2,295	47,790
Less than 1 month [member] | Forward exchange contracts [member] | Inflows [member]
Disclosure of maturity analysis for derivative financial liabilities [line items]
Gross settled	8,862,682	315,623	9,296,123
Less than 1 month [member] | Forward exchange contracts [member] | Outflows [member]
Disclosure of maturity analysis for derivative financial liabilities [line items]
Gross settled	(8,798,238)	(313,328)	(9,248,333)
Less than 1 month [member] | Swap contracts [member]
Disclosure of maturity analysis for derivative financial liabilities [line items]
Gross settled	(212,821)	(7,579)	23,251
Less than 1 month [member] | Swap contracts [member] | Inflows [member]
Disclosure of maturity analysis for derivative financial liabilities [line items]
Gross settled	19,311,999	687,749	10,187,215
Less than 1 month [member] | Swap contracts [member] | Outflows [member]
Disclosure of maturity analysis for derivative financial liabilities [line items]
Gross settled	(19,524,820)	(695,328)	(10,163,964)
Less than 1 month [member] | Target redemption forward contracts [member]
Disclosure of maturity analysis for derivative financial liabilities [line items]
Gross settled	(1,751)	(62)
Less than 1 month [member] | Target redemption forward contracts [member] | Inflows [member]
Disclosure of maturity analysis for derivative financial liabilities [line items]
Gross settled	42,720	1,522
Less than 1 month [member] | Target redemption forward contracts [member] | Outflows [member]
Disclosure of maturity analysis for derivative financial liabilities [line items]
Gross settled	(44,471)	(1,584)
1 to 3 months [member]
Disclosure of maturity analysis for derivative financial liabilities [line items]
Net settled		656
Gross settled	(264,080)	(9,404)	20,714
1 to 3 months [member] | Forward exchange contracts [member]
Disclosure of maturity analysis for derivative financial liabilities [line items]
Net settled	18,429		(13,246)
Gross settled	46,984	1,673	28,163
1 to 3 months [member] | Forward exchange contracts [member] | Inflows [member]
Disclosure of maturity analysis for derivative financial liabilities [line items]
Gross settled	5,565,137	198,189	4,420,233
1 to 3 months [member] | Forward exchange contracts [member] | Outflows [member]
Disclosure of maturity analysis for derivative financial liabilities [line items]
Gross settled	(5,518,153)	(196,516)	(4,392,070)
1 to 3 months [member] | Swap contracts [member]
Disclosure of maturity analysis for derivative financial liabilities [line items]
Gross settled	(307,124)	(10,937)	(7,449)
1 to 3 months [member] | Swap contracts [member] | Inflows [member]
Disclosure of maturity analysis for derivative financial liabilities [line items]
Gross settled	17,179,871	611,819	15,025,154
1 to 3 months [member] | Swap contracts [member] | Outflows [member]
Disclosure of maturity analysis for derivative financial liabilities [line items]
Gross settled	(17,486,997)	(622,756)	(15,032,603)
1 to 3 months [member] | Target redemption forward contracts [member]
Disclosure of maturity analysis for derivative financial liabilities [line items]
Gross settled	(3,940)	(140)
1 to 3 months [member] | Target redemption forward contracts [member] | Inflows [member]
Disclosure of maturity analysis for derivative financial liabilities [line items]
Gross settled	96,120	3,423
1 to 3 months [member] | Target redemption forward contracts [member] | Outflows [member]
Disclosure of maturity analysis for derivative financial liabilities [line items]
Gross settled	(100,060)	(3,563)
3 months to 1 year [member]
Disclosure of maturity analysis for derivative financial liabilities [line items]
Gross settled	(768,591)	(27,371)	(444,242)
3 months to 1 year [member] | Forward exchange contracts [member]
Disclosure of maturity analysis for derivative financial liabilities [line items]
Gross settled	4,456	159	2,506
3 months to 1 year [member] | Forward exchange contracts [member] | Inflows [member]
Disclosure of maturity analysis for derivative financial liabilities [line items]
Gross settled	531,336	18,922	230,354
3 months to 1 year [member] | Forward exchange contracts [member] | Outflows [member]
Disclosure of maturity analysis for derivative financial liabilities [line items]
Gross settled	(526,880)	(18,763)	(227,848)
3 months to 1 year [member] | Swap contracts [member]
Disclosure of maturity analysis for derivative financial liabilities [line items]
Gross settled	(755,972)	(26,922)	(446,748)
3 months to 1 year [member] | Swap contracts [member] | Inflows [member]
Disclosure of maturity analysis for derivative financial liabilities [line items]
Gross settled	36,739,200	1,308,376	34,327,100
3 months to 1 year [member] | Swap contracts [member] | Outflows [member]
Disclosure of maturity analysis for derivative financial liabilities [line items]
Gross settled	(37,495,172)	(1,335,298)	$ (34,773,848)
3 months to 1 year [member] | Target redemption forward contracts [member]
Disclosure of maturity analysis for derivative financial liabilities [line items]
Gross settled	(17,075)	(608)
3 months to 1 year [member] | Target redemption forward contracts [member] | Inflows [member]
Disclosure of maturity analysis for derivative financial liabilities [line items]
Gross settled	416,520	14,833
3 months to 1 year [member] | Target redemption forward contracts [member] | Outflows [member]
Disclosure of maturity analysis for derivative financial liabilities [line items]
Gross settled	(433,595)	(15,441)
Over 1 year [member]
Disclosure of maturity analysis for derivative financial liabilities [line items]
Gross settled	(8,953)	(319)
Over 1 year [member] | Target redemption forward contracts [member]
Disclosure of maturity analysis for derivative financial liabilities [line items]
Gross settled	(8,953)	(319)
Over 1 year [member] | Target redemption forward contracts [member] | Inflows [member]
Disclosure of maturity analysis for derivative financial liabilities [line items]
Gross settled	227,128	8,089
Over 1 year [member] | Target redemption forward contracts [member] | Outflows [member]
Disclosure of maturity analysis for derivative financial liabilities [line items]
Gross settled	$ (236,081)	$ (8,408)

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Detail) $ in Thousands, $ in Thousands	1 Months Ended			12 Months Ended
	Sep. 30, 2020TWD ($)shares	Jul. 31, 2019TWD ($)shares	Jul. 31, 2019USD ($)shares	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018TWD ($)	Dec. 31, 2018USD ($)
ASE Cultural and Educational Foundation [member] | Environmental charity [member]
Disclosure of transactions between related parties [line items]
Amount contributed related party transactions				$ 100,000	$ 3,561	$ 100,000	$ 3,561	$ 100,000	$ 3,561
Associates [member]
Disclosure of transactions between related parties [line items]
Real estate properties acquired | $						$ 2,326,000
ASE Environmental Protection And Sustainability Foundation [Member] | Environmental Protection Project [Member]
Disclosure of transactions between related parties [line items]
Amount contributed related party transactions				$ 100,000	$ 3,561
USI Enterprise Limited [member]
Disclosure of transactions between related parties [line items]
Repurchase of outstanding ordinary shares | shares | shares	2,685	2,805	2,805
Value of ordinary shares purchased	$ 1,520,976	$ 1,247,187	$ 54,166

Related Party Transactions - Su

Related Party Transactions - Summary of Compensation to Key Management Personnel (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Disclosure of transactions between related parties [abstract]
Short-term employee benefits	$ 1,264,980	$ 45,049	$ 1,027,191	$ 1,041,216
Post-employment benefits	2,007	72	2,208	3,884
Share-based payments	153,774	5,476	134,544	9,145
Total	$ 1,420,761	$ 50,597	$ 1,163,943	$ 1,054,245

Assets Pledged as Collateral _3

Assets Pledged as Collateral or for Security - Summary of Assets Pledged as Collateral or for Security (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)
Assets Pledged As Collateral or For Security [abstract]
Inventories related to real estate business	$ 10,564,873	$ 376,242	$ 6,063,303
Property, plant and equipment	124,124	4,420	138,831
Investment properties	11,847,145	421,907	12,167,772
Other financial assets (including current and non-current)	460,890	16,414	637,775
Total	$ 22,997,032	$ 818,983	$ 19,007,681

Assets Pledged as Collateral _4

Assets Pledged as Collateral or for Security - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2020
FAFG [Member] | Syndicated bank loans [Member]
Disclosure of detailed information about business combination [line items]
Proportion of Ownership Interest in Subsidiary Pledged as Collateral	89.60%

Significant Contingent Liabil_2

Significant Contingent Liabilities and Unrecognized Commitments - Additional Information (Detail) $ in Thousands, $ in Thousands	1 Months Ended	12 Months Ended
	Dec. 31, 2013TWD ($)	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2013USD ($)
Disclosure of contingent liabilities [line items]
Unused letters of credit		$ 2,000		$ 394,000	$ 71
Committed to purchase property, plant and equipment		32,627,411		25,119,371	1,161,945
Prepayment of property, plant and equipment		1,968,779	$ 70,113	5,145,345
Construction contract related to real estate business		602,548	$ 21,458	1,393,859
Letter of credits		$ 671,721		$ 952,001	$ 23,922
Taiwan [member]
Disclosure of contingent liabilities [line items]
Contractual period for environmental protection	30 years
Contribution to be made for environmental protection	$ 3,000,000					$ 106,838

Others - Additional Information

Others - Additional Information (Detail) ¥ in Thousands, $ in Thousands, $ in Thousands	Jun. 30, 2020CNY (¥)	Feb. 10, 2020TWD ($)	Feb. 10, 2020USD ($)	Dec. 27, 2019TWD ($)	Dec. 31, 2013TWD ($)
Disclosure Detailed Information About Others [Line Items]
Contribution received from Environmental Protection | $				$ 55,062
Procuratorate [Member]
Disclosure Detailed Information About Others [Line Items]
Administrative fine imposed | ¥	¥ 400
Income from fines and penalties | ¥	¥ 344
Original Fine [Member]
Disclosure Detailed Information About Others [Line Items]
Administrative fine imposed | $					$ 102,014
New Fine [Member]
Disclosure Detailed Information About Others [Line Items]
Administrative fine imposed		$ 46,952	$ 1,672

Significant Subsequent Events -

Significant Subsequent Events - Additional Information (Detail) - Major Debt Issuance [Member] - Unsecured Convertible Corporate Bonds [Member] - Universal Scientific Industrial (Shanghai) Co., Ltd [member] - CNY (¥) ¥ in Thousands	Mar. 01, 2021	Mar. 01, 2026	Mar. 01, 2025	Mar. 01, 2024	Mar. 01, 2023	Mar. 01, 2022
Disclosure of non-adjusting events after reporting period [line items]
Bonds face amount	¥ 3,450,000
Bonds maturity year	6 years
Annual interest rates of bonds	0.10%	2.00%	1.80%	1.30%	0.60%	0.20%

Significant Assets and Liabil_3

Significant Assets and Liabilities Denominated in Foreign Currencies - Summary of Significant Assets and Liabilities Denominated in Foreign Currencies (Detail) ¥ in Thousands, ¥ in Thousands, $ in Thousands, $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018	Dec. 31, 2020USD ($)	Dec. 31, 2020CNY (¥)	Dec. 31, 2020HKD ($)	Dec. 31, 2020JPY (¥)	Dec. 31, 2019USD ($)	Dec. 31, 2019CNY (¥)	Dec. 31, 2019JPY (¥)
US Dollar [member] | US dollar equals to New Taiwan dollar [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets	$ 121,583,265	$ 123,693,628		$ 4,269,075				$ 4,125,872
Financial liabilities	$ 126,448,786	$ 114,624,313		4,439,915				3,823,359
Exchange Rate	US$1=NT$28.48	US$1=NT$29.98	US$1=NT$30.715
Exchange Rate	US$1=NT$28.48	US$1=NT$29.98	US$1=NT$30.715
US Dollar [member] | US dollar equals to Chinese yuan [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets				1,527,381	¥ 43,499,803			1,189,539	¥ 35,662,384
Financial liabilities				1,517,568	43,220,325			1,211,472	¥ 36,319,926
Exchange Rate	US$1=RMB6.5249	US$1=RMB6.9762
Exchange Rate	US$1=RMB6.5249	US$1=RMB6.9762
US Dollar [member] | EUR equals to US dollar [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets				41,643	1,185,984
Financial liabilities				20,896	595,128
Exchange Rate	EUR1=US$0.8143
Exchange Rate	EUR1=US$0.8143
Japanese Yen [Member] | Japanese yen equals to New Taiwan dollar [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets	$ 3,742,306	$ 3,833,605					¥ 13,544,360			¥ 13,889,872
Financial liabilities		$ 4,037,478			¥ 3,773,695		13,657,967			14,628,543
Exchange Rate	JPY1=NT$0.2763	JPY1=NT$0.2760
Exchange Rate	JPY1=NT$0.2763	JPY1=NT$0.2760
Japanese Yen [Member] | Japanese yen equals to US dollar [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets				324,434			1,174,208	212,904		771,392
Financial liabilities				$ 328,424			¥ 1,188,650	$ 225,197		¥ 815,929
Exchange Rate	JPY1=US$0.0097	JPY1=US$0.0092
Exchange Rate	JPY1=US$0.0097	JPY1=US$0.0092
Hong Kong, Dollars | HK dollar equal to New Taiwan dollar [member]
Disclosure of detailed information about financial instruments [line items]
Financial assets	$ 641,912					$ 174,765
Financial liabilities	$ 69,103					$ 18,814
Exchange Rate	HKD1=NT$3.6730
Exchange Rate	HKD1=NT$3.6730

Significant Assets and Liabil_4

Significant Assets and Liabilities Denominated in Foreign Currencies - Summary of Realized and Unrealized Foreign Exchange Gain (Loss) (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Disclosure of detailed information about financial instruments [line items]
Net Foreign Exchange Gain (Loss)	$ 1,056,639	$ 37,630	$ 1,133,701	$ (1,036,715)
US Dollar [member] | US dollar equals to New Taiwan dollar [member]
Disclosure of detailed information about financial instruments [line items]
Exchange Rate	US$1=NT$28.48	US$1=NT$28.48	US$1=NT$29.98	US$1=NT$30.715
Net Foreign Exchange Gain (Loss)	$ (143,804)	$ (5,121)	$ (84,177)	$ (67,476)
New Taiwan Dollar [member]
Disclosure of detailed information about financial instruments [line items]
Net Foreign Exchange Gain (Loss)	$ 1,382,067	$ 49,219	$ 1,203,823	$ (849,234)
Chinese Yuan [member] | Chinese Yuan equals to New Taiwan dollar [member]
Disclosure of detailed information about financial instruments [line items]
Exchange Rate	RMB1=NT$4.3648	RMB1=NT$4.3648	RMB1=NT$4.2975	RMB1=NT$4.4753
Net Foreign Exchange Gain (Loss)	$ (181,624)	$ (6,468)	$ 14,055	$ (120,005)

Operating Segments Informatio_2

Operating Segments Information - Summary of Segment Information (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018TWD ($)	Dec. 31, 2020USD ($)
Disclosure of operating segments [line items]
Operating revenue	$ 476,978,710	$ 16,986,421	$ 413,182,184		$ 371,092,421
Interest income	520,783	18,546	549,681		466,211
Interest expense	(3,437,228)	(122,409)	(4,186,855)		(3,535,886)
Depreciation and amortization	(51,259,065)	(1,825,465)	(50,466,841)		(42,688,903)
Share of the profit or loss of associates and joint ventures	547,612	19,502	182,275		(480,244)
Impairment loss	(992,273)	(35,337)	(601,207)	$ (141)	(654,081)
Segment profit before income tax	35,768,798	1,273,817	23,279,811		31,937,678
Expenditures for segment assets	59,024,201	2,102,001	63,073,887		39,092,238
Investments accounted for using the equity method	12,806,673		12,085,207		9,312,308	$ 456,078
Contract assets	4,782,904		5,897,316		4,488,500	170,331
Packaging segment [member]
Disclosure of operating segments [line items]
Operating revenue	218,666,071	7,787,253	198,916,897		178,308,222
Interest income	133,160	4,742	186,291		166,761
Interest expense	(2,244,280)	(79,925)	(3,403,475)		(3,647,601)
Depreciation and amortization	(32,333,229)	(1,151,468)	(33,456,831)		(29,491,977)
Share of the profit or loss of associates and joint ventures	362,133	12,896	75,303		(456,846)
Impairment loss	(218,600)	(7,785)	(601,066)		(654,081)
Segment profit before income tax	17,476,440	622,380	7,572,763		17,866,431
Expenditures for segment assets	38,643,303	1,376,186	35,462,305		22,787,190
Investments accounted for using the equity method	9,146,344		8,867,316		9,152,290	325,724
Contract assets	3,641,244		4,162,124		3,488,372	129,674
Testing segment [member]
Disclosure of operating segments [line items]
Operating revenue	47,271,074	1,683,443	42,658,686		35,903,202
Interest income	79,821	2,842	90,091		55,108
Interest expense	(564,269)	(20,095)	(545,609)		(101,338)
Depreciation and amortization	(14,189,024)	(505,307)	(12,379,703)		(9,560,610)
Share of the profit or loss of associates and joint ventures	99,670	3,550	39,852		(23,398)
Impairment loss	(773,673)	(27,552)
Segment profit before income tax	10,277,760	366,017	10,321,537		7,952,484
Expenditures for segment assets	14,275,397	508,383	23,966,051		12,991,023
Investments accounted for using the equity method	1,340,307		1,123,490		160,018	47,732
Contract assets	1,141,660		1,735,192		1,000,128	40,657
EMS segment [member]
Disclosure of operating segments [line items]
Operating revenue	204,690,669	7,289,554	165,789,479		151,890,384
Interest income	275,766	9,821	249,487		354,343
Interest expense	(443,519)	(15,795)	(255,404)
Depreciation and amortization	(2,877,546)	(102,477)	(2,534,825)		(2,065,590)
Share of the profit or loss of associates and joint ventures	85,809	3,056	67,120
Segment profit before income tax	8,438,766	300,526	6,082,106		6,225,984
Expenditures for segment assets	5,614,409	199,943	2,770,129		2,529,771
Investments accounted for using the equity method	2,320,022		2,094,401			$ 82,622
All other segments [member]
Disclosure of operating segments [line items]
Operating revenue	6,350,896	226,171	5,817,122		4,990,613
Interest income	32,036	1,141	284,458		352,232
Interest expense	(185,160)	(6,594)	(243,013)		(249,180)
Depreciation and amortization	(1,859,266)	(66,213)	(2,095,482)		(1,570,726)
Impairment loss					0
Segment profit before income tax	(424,168)	(15,106)	(696,595)		(107,221)
Expenditures for segment assets	491,092	17,489	875,402		784,254
Adjustments and Eliminations [member]
Disclosure of operating segments [line items]
Interest income			(260,646)		(462,233)
Interest expense			260,646		462,233
Inter-group revenues [member] | Packaging segment [member]
Disclosure of operating segments [line items]
Operating revenue	10,436,168	371,659	5,370,963		3,531,431
Inter-group revenues [member] | Testing segment [member]
Disclosure of operating segments [line items]
Operating revenue	435,587	15,512	231,399		212,310
Inter-group revenues [member] | EMS segment [member]
Disclosure of operating segments [line items]
Operating revenue	21,472,775	764,700	60,638,567		58,836,465
Inter-group revenues [member] | All other segments [member]
Disclosure of operating segments [line items]
Operating revenue	7,234,303	257,632	7,431,399		7,637,053
Inter-group revenues [member] | Adjustments and Eliminations [member]
Disclosure of operating segments [line items]
Operating revenue	(39,578,833)	(1,409,503)	(73,672,328)		(70,217,259)
Operating segment [member]
Disclosure of operating segments [line items]
Operating revenue	516,557,543	18,395,924	486,854,512		441,309,680
Operating segment [member] | Packaging segment [member]
Disclosure of operating segments [line items]
Operating revenue	229,102,239	8,158,912	204,287,860		181,839,653
Operating segment [member] | Testing segment [member]
Disclosure of operating segments [line items]
Operating revenue	47,706,661	1,698,955	42,890,085		36,115,512
Operating segment [member] | EMS segment [member]
Disclosure of operating segments [line items]
Operating revenue	226,163,444	8,054,254	226,428,046		210,726,849
Operating segment [member] | All other segments [member]
Disclosure of operating segments [line items]
Operating revenue	$ 13,585,199	$ 483,803	$ 13,248,521		$ 12,627,666

Operating Segments Informatio_3

Operating Segments Information - Summary of Revenue from Major Products and Services (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Disclosure of products and services [line items]
Operating revenue	$ 476,978,710	$ 16,986,421	$ 413,182,184	$ 371,092,421
Packaging service [member]
Disclosure of products and services [line items]
Operating revenue	218,666,071	7,787,253	198,916,897	178,308,222
Testing service [member]
Disclosure of products and services [line items]
Operating revenue	47,271,074	1,683,443	42,658,686	35,903,202
EMS
Disclosure of products and services [line items]
Operating revenue	204,690,669	7,289,554	165,789,479	151,890,384
Other products and services [member]
Disclosure of products and services [line items]
Operating revenue	$ 6,350,896	$ 226,171	$ 5,817,122	$ 4,990,613

Operating Segments Informatio_4

Operating Segments Information - Summary of Geographical Information (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)	Dec. 31, 2020USD ($)
Disclosure of geographical areas [line items]
Operating revenue	$ 476,978,710	$ 16,986,421	$ 413,182,184	$ 371,092,421
Noncurrent assets, excluding financial instruments, post-employment benefit assets and deferred tax assets	337,369,625		334,926,069		$ 12,014,588
United States [Member]
Disclosure of geographical areas [line items]
Operating revenue	297,117,001	10,581,090	245,521,027	230,791,164
Taiwan [member]
Disclosure of geographical areas [line items]
Operating revenue	64,829,301	2,308,736	51,244,470	45,630,792
Noncurrent assets, excluding financial instruments, post-employment benefit assets and deferred tax assets	239,353,978		239,532,971		8,524,002
Asia [Member]
Disclosure of geographical areas [line items]
Operating revenue	74,447,091	2,651,249	75,938,364	56,031,108
Europe [Member]
Disclosure of geographical areas [line items]
Operating revenue	39,477,306	1,405,887	38,613,132	36,844,258
Other geographical areas [member]
Disclosure of geographical areas [line items]
Operating revenue	1,108,011	$ 39,459	1,865,191	$ 1,795,099
Noncurrent assets, excluding financial instruments, post-employment benefit assets and deferred tax assets	34,107,657		26,645,450		1,214,660
China [member]
Disclosure of geographical areas [line items]
Noncurrent assets, excluding financial instruments, post-employment benefit assets and deferred tax assets	$ 63,907,990		$ 68,747,648		$ 2,275,926

Operating Segments Informatio_5

Operating Segments Information - Additional Information (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020TWD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019TWD ($)	Dec. 31, 2018TWD ($)
Disclosure of operating segments [line items]
Operating revenue	$ 476,978,710	$ 16,986,421	$ 413,182,184	$ 371,092,421
Packaging and EMS segments [member] | Customer One [member]
Disclosure of operating segments [line items]
Operating revenue	$ 145,952,908	$ 5,197,753	103,987,781	$ 92,117,839
Packaging And Testing segments [member] | Customer Two [member]
Disclosure of operating segments [line items]
Operating revenue			$ 44,653,072