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Trade Notes and Accounts Receivable, Net - Additional Information (Detail) | 12 Months Ended
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Dec. 31, 2017
Disclosure of financial assets [Line Items] |
Threshold period when notes and accounts receivable due are unlikely to be collected and therefore the allowance of notes and accounts receivable are recognized | 180 days
Percentage of allowance of notes and accounts receivable overdue recognized | 100.00%
Minimum [Member] |
Disclosure of financial assets [Line Items] |
Average credit terms | 30 days
Top of range [Member] |
Disclosure of financial assets [Line Items] |
Average credit terms | 90 days

X
- Definition Average credit terms. + References No definition available. + Details
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Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of allowance of notes and accounts receivable overdue recognized. + References No definition available. + Details
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Namespace Prefix: | cht_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Recovery period allowed for notes and accounts receivable. + References No definition available. + Details
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Balance Type: | na
Period Type: | duration

X
- Definition Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes of the table. + References No definition available. + Details
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Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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

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