Other Current Monetary Assets - Summary of Other Current Monetary Assets (Detail) $ in Millions, $ in Millions	Dec. 31, 2017 TWD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 TWD ($)
Disclosure Of Other Current Monetary Assets [Abstract]
Time deposits and negotiable certificates of deposit with maturities of more than three months	$ 4,054		$ 3,568
Others	1,254		1,253
Other current monetary assets	$ 5,308	$ 179	$ 4,821

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 2016-01-13
-Paragraph 54
-Subparagraph d
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2016-03-30&anchor=para_54_d&doctype=Standard
-URIDate 2016-03-31

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