XML 152 R137.htm IDEA: XBRL DOCUMENT
v3.19.1

Hedging Derivative Financial Instruments - Loss (Gain) Arising from Hedging Derivative Financial Instruments that have been Reclassified from Equity to Initial Cost of the Property, Plant and Equipment (Detail) - TWD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016
Disclosure Of Detailed Information About Hedging Instruments [Abstract] |  |
Construction in progress and equipment to be accepted | $ (2) | $ (15)

X
- Definition Loss (gain) arising from the hedging derivative financial instruments that have been reclassified from equity to initial cost of property plant and equipment. + References No definition available. + Details
Name: | cht_LossGainArisingFromHedgingDerivativeFinancialInstrumentsReclassifiedFromEquityToInitialCostOfPropertyPlantAndEquipment
Namespace Prefix: | cht_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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