Operating Lease Arrangements - Additional Information (Detail) $ in Thousands, $ in Thousands	12 Months Ended
Dec. 31, 2017 TWD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 TWD ($)	Dec. 31, 2015 TWD ($)
Lease and sublease payments recognised as expense [abstract]
Operating lease expiration	2018 to 2023	2018 to 2023
Rental expense	$ 1,193,477	$ 40,266	$ 1,411,533	$ 1,390,821

The amount of payments on leases and subleases recognised as an expense by the lessee.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Note Expiry date 2019-01-01
-Name IAS
-Number 17
-IssueDate 2017-01-01
-Paragraph 35
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=17&date=2017-03-02&anchor=para_35_c&doctype=Standard&book=B
-URIDate 2017-03-09

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