The amount of impairment loss recognised in profit or loss for property, plant and equipment. [Refer: Impairment loss recognised in profit or loss; Property, plant and equipment]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 16
-IssueDate 2016-01-13
-Paragraph 73
-Subparagraph e
-Clause v
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=16&date=2016-03-30&anchor=para_73_e_v&doctype=Standard
-URIDate 2016-03-31

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2016-01-13
-Paragraph 98
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2016-03-30&anchor=para_98_a&doctype=Standard
-URIDate 2016-03-31

Name:	ifrs-full_ImpairmentLossRecognisedInProfitOrLossPropertyPlantAndEquipment
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

Property, Plant and Equipment - Additional Information (Detail) $ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2017 TWD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 TWD ($)	Dec. 31, 2015 TWD ($)
Disclosure of detailed information about property, plant and equipment [Line Items]
Impairment losses	$ 0.0	$ 0	$ 596.0	$ 138.0
Telecommunications equipment [Member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Impairment losses			596.0	$ 138.0
Partial computer and miscellaneous equipment [Member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Impairment losses			$ 0.4