Income Tax - Summary of Income Tax Recognized Directly in Equity (Detail) $ in Thousands, $ in Thousands	12 Months Ended
Dec. 31, 2020 TWD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 TWD ($)	Dec. 31, 2018 TWD ($)
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)

The amount of deferred tax related to items credited (charged) directly to equity. [Refer: Deferred tax expense (income)]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 12
-IssueDate 2020-01-01
-Paragraph 81
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=12&code=ifrs-tx-2020-en-r&anchor=para_81_a&doctype=Standard
-URIDate 2020-01-01

Name:	ifrs-full_DeferredTaxRelatingToItemsChargedOrCreditedDirectlyToEquity
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration