Other Current Monetary Assets - Summary of Other Current Monetary Assets (Detail) $ in Millions, $ in Millions	Dec. 31, 2018 TWD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 TWD ($)
Disclosure Of Other Current Monetary Assets [Abstract]
Time deposits and negotiable certificates of deposit with maturities of more than three months	$ 8,157		$ 4,054
Others	1,347		1,254
Other current monetary assets	$ 9,504	$ 310	$ 5,308

The amount of current financial assets that the entity does not separately disclose in the same statement or note. [Refer: Other financial assets; Current financial assets]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2018-01-01
-Paragraph 54
-Subparagraph d
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_54_d&doctype=Standard
-URIDate 2018-03-16

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