Equity - Appropriations of Earnings (Detail) - TWD ($) $ / shares in Units, $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash dividends per share	$ 4.226	$ 4.479	$ 4.796
Reversal of special reserve [Member]
Appropriations of earnings			$ 5
Cash dividends [Member]
Appropriations of earnings	$ 32,783	$ 34,746	$ 37,205

The amount, per share, of dividends proposed or declared before financial statements were authorised for issue but not recognised as distribution to owners.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2019-01-01
-Paragraph 137
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2019-en-r&anchor=para_137_a&doctype=Standard
-URIDate 2019-03-27

Name:	ifrs-full_DividendsProposedOrDeclaredBeforeFinancialStatementsAuthorisedForIssueButNotRecognisedAsDistributionToOwnersPerShare
Namespace Prefix:	ifrs-full_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration