Contents of Significant Accounts - Short-Term Loans - Additional Information (Detail) - TWD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Short term lines of credit [member]
Disclosure of detailed information about borrowings [line items]
Unused short-term lines of credit	$ 64,169	$ 77,658

The amount of undrawn borrowing facilities that may be available for future operating activities and to settle capital commitments. [Refer: Capital commitments]

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Name IAS
-Number 7
-IssueDate 2019-01-01
-Paragraph 50
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=7&code=ifrs-tx-2019-en-r&anchor=para_50_a&doctype=Standard
-URIDate 2019-03-27

Name:	ifrs-full_UndrawnBorrowingFacilities
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant