Lease Arrangements - Summary of Lease Liabilities (Details) $ in Millions, $ in Millions	Dec. 31, 2020 TWD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 TWD ($)
Disclosure Of Quantitative Information About Leases For Lessee [Abstract]
Lease liabilities - current	$ 3,382	$ 120	$ 3,291
Lease liabilities - noncurrent	6,215	$ 221	6,467
Lease liabilities	$ 9,597		$ 9,758

The amount of current lease liabilities. [Refer: Lease liabilities]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 16
-IssueDate 2020-01-01
-Paragraph 47
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=16&code=ifrs-tx-2020-en-r&anchor=para_47_b&doctype=Standard
-URIDate 2020-01-01

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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- References

No definition available.

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- Definition

The amount of liabilities related to the entity's leases. Lease is a contract, or part of a contract, that conveys the right to use an underlying asset for a period of time in exchange for consideration.

+ References

+ Details

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Period Type:	instant

- Definition

The amount of non-current lease liabilities. [Refer: Lease liabilities]

+ References

+ Details

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