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v3.19.1

Trade Notes and Accounts Receivable, Net - Additional Information (Detail) | 12 Months Ended
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Dec. 31, 2018 | 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%
Bottom of Range [Member] |  |
Disclosure Of Financial Assets [Line Items] |  |
Average credit terms | 30 days | 30 days
Top of Range [Member] |  |
Disclosure Of Financial Assets [Line Items] |  |
Average credit terms | 90 days | 90 days

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

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- 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

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

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- 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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Balance Type: | na
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- Details
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Balance Type: |
Period Type: |

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