Related Parties Transactions - Compensation of Directors and Other Key Management Personnel (Detail) - TWD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disclosure Of Transactions Between Related Parties [Abstract]
Short-term employee benefits	$ 263	$ 282	$ 254
Post-employment benefits	9	10	9
Share-based payment	0	9	2
Compensation of key management personnel	$ 272	$ 301	$ 265

No definition available.

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- Definition

The amount of compensation to key management personnel. [Refer: Key management personnel of entity or parent [member]]

+ References

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- Definition

The amount of compensation to key management personnel in the form of post-employment benefits. [Refer: Key management personnel of entity or parent [member]]

+ References

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- Definition

The amount of compensation to key management personnel in the form of share-based payments. [Refer: Key management personnel of entity or parent [member]]

+ References

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- Definition

The amount of compensation to key management personnel in the form of short-term employee benefits. [Refer: Key management personnel of entity or parent [member]]

+ References

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