Contents of Significant Accounts - Summary of Income Recognized in Profit or Loss from Equity Instruments Designated as Fair Value Through Other Comprehensive Income (Detail) - TWD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Dividend Income [Abstract]
Held at end of period	$ 286,795	$ 365,052
Total	$ 286,795	$ 365,052

The amount of dividends related to investments in equity instruments that the entity has designated at fair value through other comprehensive income, held at the end of the reporting period. [Refer: Investments in equity instruments designated at fair value through other comprehensive income [member]]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 7
-IssueDate 2020-01-01
-Paragraph 11A
-Subparagraph d
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2020-en-r&anchor=para_11A_d&doctype=Standard
-URIDate 2020-01-01

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