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Advance Receipt - Additional Information (Detail) $ in Millions | Dec. 31, 2017 TWD ($)
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Miscellaneous Current Liabilities [Abstract] |
Performance guarantee for advance receipts from selling prepaid cards | $ 797

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- Definition Performance guarantee for advance receipts from selling prepaid cards. + References No definition available. + Details
Name: | cht_PerformanceGuaranteeForAdvanceReceiptsFromSellingPrepaidCards
Namespace Prefix: | cht_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- References No definition available. + Details
Name: | ifrs-full_MiscellaneousCurrentLiabilitiesAbstract
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration