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General - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2018
General Information [Abstract]
Description of percentage of ownership interes	below 50%

X

- Definition

Description of percentage of portion of ownership interest.

+ References

No definition available.

+ Details

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

X

- Definition

General information.

+ References

No definition available.

+ Details

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