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Short-term Bills Payable - Summary of Annual Interest Rates of Commercial Paper Payable (Detail) | Dec. 31, 2020
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Bottom of Range [Member] |
Short Term Bills Payable [Line Items] |
Commercial paper payable | 0.34%
Top of Range [Member] |
Short Term Bills Payable [Line Items] |
Commercial paper payable | 0.36%

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- Definition Annual interest rates of commercial paper payable. + References No definition available. + Details
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Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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- Definition Short-term bills payable. + 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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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |