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Revenue - Summary of Changes in Contract Assets and Contract Liabilities (Detail) - TWD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2019 | Dec. 31, 2018
Contract assets |  |
Net increase of customer contracts | $ 6,066 | $ 4,126
Reclassified to trade receivables | (6,405) | (7,532)
Significant changes of contract assets | (339) | (3,406)
Contract liabilities |  |
Net increase of customer contracts | 22 | 16
Recognized as revenues | (89) | (194)
Significant changes of contract liabilities | $ (67) | $ (178)

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- Definition Decrease in contract asset through reclassification to trade receivables. + References No definition available. + Details
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- Definition Decrease in contract liabilities revenue recognition. + References No definition available. + Details
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Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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- Definition Increase in contract asset through increase in customer contracts. + References No definition available. + Details
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- Definition Increase in contract liabilities through increase in customer contracts. + References No definition available. + Details
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- Definition Significant changes of contract assets. + References No definition available. + Details
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- Definition Significant changes of contract liabilities. + References No definition available. + Details
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Namespace Prefix: | cht_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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- References No definition available. + Details
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Period Type: | duration

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- References No definition available. + Details
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Balance Type: | na
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