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Net Income and Other Comprehensive Income (Loss) - Additional Information (Detail) $ in Millions | 12 Months Ended
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Dec. 31, 2017 TWD ($)
Employee Benefits Expense [Line Items] |
Employees' compensation payables | $ 1,596
Remuneration to directors payables | $ 41
Minimum [Member] |
Employee Benefits Expense [Line Items] |
Employees' compensation distribution rate | 1.70%
Top of range [Member] |
Employee Benefits Expense [Line Items] |
Employees' compensation distribution rate | 4.30%
Directors' remuneration distribution rate | 0.17%

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- Definition Directors' remuneration distribution percentage. + References No definition available. + Details
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Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- Definition Employee benefits expense. + References No definition available. + Details
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Balance Type: | na
Period Type: | duration

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- Definition Employee compensation distribution percentage. + References No definition available. + Details
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Namespace Prefix: | cht_
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Balance Type: | na
Period Type: | duration

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- Definition Employees' compensation payables. + References No definition available. + Details
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Namespace Prefix: | cht_
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Balance Type: | credit
Period Type: | instant

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- Definition Remuneration to directors payables. + References No definition available. + Details
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Namespace Prefix: | cht_
Data Type: | xbrli:monetaryItemType
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Period Type: | instant

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

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- Details
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Namespace Prefix: |
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Balance Type: |
Period Type: |