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v3.8.0.1

General - Additional Information (Detail) | 12 Months Ended
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Dec. 31, 2017
General Information [Abstract] |
Description of percentage of ownership interes | below 50%

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- 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

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- Definition General information. + References No definition available. + Details
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Namespace Prefix: | cht_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration