Financial Assets at Fair Value through Other Comprehensive Income Noncurrent - Additional Information (Detail) $ in Millions	12 Months Ended
Dec. 31, 2018 TWD ($)
Noncurrent Financial Assets At Fair Value Through Other Comprehensive Income [Abstract]
Dividends received	$ 396

The amount of dividends received.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2018-01-01
-Paragraph B12
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=12&date=2018-03-01&anchor=para_B12_a&doctype=Appendix&seq=2
-URIDate 2018-03-16

Name:	ifrs-full_DividendsReceived
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration