Lease Arrangements - Summary of Total Cash Outflow for Leases (Details) $ in Millions	12 Months Ended
Dec. 31, 2019 TWD ($)
Disclosure Of Quantitative Information About Leases For Lessee [Abstract]
Expenses relating to low-value asset leases	$ 7
Expenses relating to variable lease payments not included in the measurement of lease liabilities	6
Total cash outflow for leases	$ 3,826

The cash outflow for leases.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 16
-IssueDate 2019-01-01
-Paragraph 53
-Subparagraph g
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=16&code=ifrs-tx-2019-en-r&anchor=para_53_g&doctype=Standard
-URIDate 2019-03-27

+ Details

Name:	ifrs-full_CashOutflowForLeases
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- References

No definition available.

+ Details

Name:	ifrs-full_DisclosureOfQuantitativeInformationAboutLeasesForLesseeAbstract
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of the expense relating to leases of low-value assets accounted for applying paragraph 6 of IFRS 16. This expense shall not include the expense relating to short-term leases of low-value assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 16
-IssueDate 2019-01-01
-Paragraph 53
-Subparagraph d
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=16&code=ifrs-tx-2019-en-r&anchor=para_53_d&doctype=Standard
-URIDate 2019-03-27

+ Details

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

- Definition

The amount of the expense relating to variable lease payments not included in the measurement of lease liabilities. Variable lease payments are the portion of payments made by a lessee to a lessor for the right to use an underlying asset during the lease term that varies because of changes in facts or circumstances occurring after the commencement date, other than the passage of time. [Refer: Lease liabilities]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 16
-IssueDate 2019-01-01
-Paragraph 53
-Subparagraph e
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=16&code=ifrs-tx-2019-en-r&anchor=para_53_e&doctype=Standard
-URIDate 2019-03-27

+ Details

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