The amount of investments accounted for using the equity method. The equity method is a method of accounting whereby the investment is initially recognised at cost and adjusted thereafter for the post-acquisition change in the investor's share of net assets of the investee. The investor's profit or loss includes its share of the profit or loss of the investee. The investor's other comprehensive income includes its share of the other comprehensive income of the investee. [Refer: At cost [member]]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 8
-IssueDate 2020-01-01
-Paragraph 24
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=8&code=ifrs-tx-2020-en-r&anchor=para_24_a&doctype=Standard
-URIDate 2020-01-01

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2020-01-01
-Paragraph B16
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=12&code=ifrs-tx-2020-en-r&anchor=para_B16&doctype=Appendix&subtype=B
-URIDate 2020-01-01

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2020-01-01
-Paragraph 54
-Subparagraph e
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2020-en-r&anchor=para_54_e&doctype=Standard
-URIDate 2020-01-01

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

Contents of Significant Accounts - Investments Accounted For Under the Equity Method - Additional Information (Detail) $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020 TWD ($)	Dec. 31, 2019 TWD ($)	Dec. 31, 2018 TWD ($)	Dec. 31, 2020 USD ($)
Investments in associates and joint ventures [line items]
Investments accounted for using equity method for which there are published price quotations	$ 20,330,138	$ 9,564,517		$ 724,008
Aggregated individually immaterial associates and joint ventures [member]
Investments in associates and joint ventures [line items]
Exchange differences arising from translation of the foreign entity	(53,000)	(9,000)	$ (16,000)
Investments with published price quotations [member]
Investments in associates and joint ventures [line items]
Investments accounted for using equity method for which there are published price quotations	10,657,000	1,750,000
Investments with published price quotations [member] \| Fair value [member]
Investments in associates and joint ventures [line items]
Investments accounted for using equity method for which there are published price quotations	$ 18,885,000	$ 2,244,000