Financial Assets at Amortized Cost - Summary of Financial Assets at Amortized Cost (Detail) - TWD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Financial Instruments At Amortised Cost Category[abstract]
Time deposits	$ 206,482	$ 168,970
Restricted bank deposits	48,319	68,450
Interest income	$ 2,206	$ 4,467	$ 920

The amount of revenue arising from interest for financial assets that are measured at amortised cost. [Refer: Interest income; Financial assets at amortised cost]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 7
-IssueDate 2020-01-01
-Paragraph 20
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2020-en-r&anchor=para_20_b&doctype=Standard
-URIDate 2020-01-01

Name:	ifrs-full_InterestIncomeForFinancialAssetsMeasuredAtAmortisedCost
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration