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Revenue - Summary of Revenue Recognized (Detail) $ in Millions | 12 Months Ended
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Dec. 31, 2018 TWD ($)
Revenue From Contract With Customer [Abstract] |
Telecommunications business | $ 7,157
Project business | 627
Others | 324
Contracts with customers revenue recognized | $ 8,108

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- Definition Contracts with customers revenue recognized. + References No definition available. + Details
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Balance Type: | credit
Period Type: | duration

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- Definition Revenue from others services. + References No definition available. + Details
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Period Type: | duration

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- Definition Revenue from project business. + References No definition available. + Details
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Namespace Prefix: | cht_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Definition Revenue from telecommunications business. + References No definition available. + Details
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Namespace Prefix: | cht_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- References No definition available. + Details
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Namespace Prefix: | us-gaap_
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Period Type: | duration