XML 227 R212.htm IDEA: XBRL DOCUMENT
v3.19.1

Fair Value Information - Schedule of Impact of Decrease in Discount for Lack of Marketability or Noncontrolling Interests (Detail) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2018 TWD ($)
Disclosure Of Fair Value Measurement Of Financial Instruments [Abstract] |
Discount for lack of marketability 5% decrease | $ 268
Noncontrolling interests discount 5% decrease | $ 37

X
- Definition Amount of discount for lack of marketability five percentage decrease. + References No definition available. + Details
Name: | cht_AmountOfDiscountForLackOfMarketabilityFivePercentageDecrease
Namespace Prefix: | cht_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of Noncontrolling interests discount five percentage decrease. + References No definition available. + Details
Name: | cht_AmountOfNoncontrollingInterestsDiscountFivePercentageDecrease
Namespace Prefix: | cht_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Disclosure of fair value measurement of financial instruments. + References No definition available. + Details
Name: | cht_DisclosureOfFairValueMeasurementOfFinancialInstrumentsAbstract
Namespace Prefix: | cht_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration