Inventories Related to Real Estate Business - Additional Information (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2017 TWD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 TWD ($)
Disclosure of detailed information about property, plant and equipment [Line Items]
Investment properties	$ 8,119,436	$ 273,935
Inventories related to real estate business expected to be recovered longer than twelve months	9,818,869	331,271	$ 12,076,154
Reclassified of buildings and land use right under the line item of "inventories related to real estate - construction in progress" [Member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Investment properties	6,971,372	235,201
Long-term prepayments for lease	$ 5,798,449	$ 195,629

Expiry date 2019-01-01: The amount of property (land or a building - or part of a building - or both) held (by the owner or by the lessee under a finance lease) to earn rentals or for capital appreciation or both, rather than for: (a) use in the production or supply of goods or services or for administrative purposes; or (b) sale in the ordinary course of business. Effective 2019-01-01: The amount of property (land or a building - or part of a building - or both) held (by the owner or by the lessee as a right-of-use asset) to earn rentals or for capital appreciation or both, rather than for: (a) use in the production or supply of goods or services or for administrative purposes; or (b) sale in the ordinary course of business.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 40
-IssueDate 2017-01-01
-Paragraph 76
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=40&date=2017-03-01&anchor=para_76&doctype=Standard
-URIDate 2017-03-09

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 40
-IssueDate 2017-01-01
-Paragraph 79
-Subparagraph d
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=40&date=2017-03-01&anchor=para_79_d&doctype=Standard
-URIDate 2017-03-09

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2017-01-01
-Paragraph 54
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_54_b&doctype=Standard
-URIDate 2017-03-09

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