Operating Lease Arrangements - Future Aggregate Minimum Lease Collection Under Non-cancellable Operating Leases (Detail) - TWD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Disclosure of finance lease and operating lease by lessor [Line Items]
Minimum lease collection under non-cancellable operating leases	$ 1,130	$ 1,255
Within one year [Member]
Disclosure of finance lease and operating lease by lessor [Line Items]
Minimum lease collection under non-cancellable operating leases	344	353
1-5 Years [Member]
Disclosure of finance lease and operating lease by lessor [Line Items]
Minimum lease collection under non-cancellable operating leases	580	659
More Than 5 Year [Member]
Disclosure of finance lease and operating lease by lessor [Line Items]
Minimum lease collection under non-cancellable operating leases	$ 206	$ 243

The amount of future minimum lease payments receivable under non-cancellable operating leases. Minimum lease payments are payments over the lease term that the lessee is or can be required to make, excluding contingent rent, costs for services and taxes to be paid by, and reimbursed to, the lessor, together with: (a) for a lessee, any amounts guaranteed by the lessee or by a party related to the lessee; or (b) for a lessor, any residual value guaranteed to the lessor by: (i) the lessee; (ii) a party related to the lessee; or (iii) a third party unrelated to the lessor that is financially capable of discharging the obligations under the guarantee.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Note Expiry date 2019-01-01
-Name IAS
-Number 17
-IssueDate 2018-01-01
-Paragraph 56
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=17&date=2018-03-02&anchor=para_56_a&doctype=Standard&book=b
-URIDate 2018-03-16

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