Equity - Appropriations of Earnings (Detail) - TWD ($) $ / shares in Units, $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash dividends per share	$ 4.479	$ 4.796	$ 4.9419
Special reserve [Member]
Appropriations of earnings		$ (5)	$ 5
Cash dividends [member]
Appropriations of earnings	$ 34,746	$ 37,205	$ 38,336

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 2018-01-01
-Paragraph 137
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_137_a&doctype=Standard
-URIDate 2018-03-16

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