Capital Management - Percentages of Liabilities to Assets Ratio Used for Monitoring Capital (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2020 TWD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 TWD ($)
Disclosure of objectives, policies and processes for managing capital [abstract]
Total liabilities	$ 14,364,975	$ 511,573	$ 14,775,302
Total assets	$ 35,080,814	$ 1,249,317	$ 34,305,887
Liabilities to assets ratio	40.95%	40.95%	43.07%

The amount of a present economic resource controlled by the entity as a result of past events. Economic resource is a right that has the potential to produce economic benefits.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 13
-IssueDate 2020-01-01
-Paragraph 93
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=13&code=ifrs-tx-2020-en-r&anchor=para_93_a&doctype=Standard
-URIDate 2020-01-01

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 8
-IssueDate 2020-01-01
-Paragraph 28
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=8&code=ifrs-tx-2020-en-r&anchor=para_28_c&doctype=Standard
-URIDate 2020-01-01

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 13
-IssueDate 2020-01-01
-Paragraph 93
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=13&code=ifrs-tx-2020-en-r&anchor=para_93_b&doctype=Standard
-URIDate 2020-01-01

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 13
-IssueDate 2020-01-01
-Paragraph 93
-Subparagraph e
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=13&code=ifrs-tx-2020-en-r&anchor=para_93_e&doctype=Standard
-URIDate 2020-01-01

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2020-01-01
-Paragraph 55
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2020-en-r&anchor=para_55&doctype=Standard
-URIDate 2020-01-01

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 8
-IssueDate 2020-01-01
-Paragraph 23
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=8&code=ifrs-tx-2020-en-r&anchor=para_23&doctype=Standard
-URIDate 2020-01-01

Name:	ifrs-full_Assets
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant