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Other Assets - Additional Information (Detail $ in Millions	12 Months Ended
	Dec. 31, 2019 TWD ($)
Disclosure Of Other Assets [Abstract]
Impairment loss on other assets	$ 44

X

- Definition

Disclosure of other assets.

+ References

No definition available.

+ Details

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Namespace Prefix:	cht_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

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- Definition

Impairment loss recognised in profit or loss other assets.

+ References

No definition available.

+ Details

Name:	cht_ImpairmentLossRecognisedInProfitOrLossOtherAssets
Namespace Prefix:	cht_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration