XML 234 R218.htm IDEA: XBRL DOCUMENT
v3.21.1

Financial Instruments - Additional Information (Detail) - TWD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Foreign currency risk [Member] |  |  |
Disclosure of detailed information about financial instruments [Line Items] |  |  |
Sensitivity rate | 5.00% | 5.00% | 5.00%
Interest rate risk [member] |  |  |
Disclosure of detailed information about financial instruments [Line Items] |  |  |
Sensitivity rate | 0.25% | 0.25% | 0.25%
Increase decrease in pre-tax income due to sensitivity analysis | $ 19 | $ 15 | $ 19
Equity price risk [Member] |  |  |
Disclosure of detailed information about financial instruments [Line Items] |  |  |
Sensitivity rate | 5.00% | 5.00% | 5.00%
Equity price risk [Member] | Pre-tax profit [Member] |  |  |
Disclosure of detailed information about financial instruments [Line Items] |  |  |
Increase decrease in pretax income of financial assets at FVTPL, FVOCI | $ 34 | $ 39 | $ 26
Equity price risk [Member] | Pre-tax other comprehensive income [Member] |  |  |
Disclosure of detailed information about financial instruments [Line Items] |  |  |
Increase decrease in pretax income of financial assets at FVTPL, FVOCI | $ 360 | $ 358 | $ 347

X
- Definition Increase decrease pre-tax profit and pre-tax other comprehensive income of financial assets at FVTOCI. + References No definition available. + Details
Name: | cht_IncreaseDecreasePreTaxProfitAndPreTaxOtherComprehensiveIncomeOfFinancialAssetsAtFVTOCI
Namespace Prefix: | cht_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Risk exposure associated with instruments sharing characteristic, percentage change in risk. + References No definition available. + Details
Name: | cht_RiskExposureAssociatedWithInstrumentsSharingCharacteristicPercentageChangeInRisk
Namespace Prefix: | cht_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes of the table. + References No definition available. + Details
Name: | ifrs-full_DisclosureOfFinancialInstrumentsLineItems
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The amount of risk exposure associated with financial instruments with a shared characteristic that identifies a concentration of risks. [Refer: Financial instruments, class [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 7 -IssueDate 2020-01-01 -Paragraph B8 -Subparagraph c -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2020-en-r&anchor=para_B8_c&doctype=Appendix&subtype=B -URIDate 2020-01-01 + Details
Name: | ifrs-full_RiskExposureAssociatedWithInstrumentsSharingCharacteristic
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | ifrs-full_TypesOfRisksAxis=ifrs-full_CurrencyRiskMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_TypesOfRisksAxis=ifrs-full_InterestRateRiskMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_TypesOfRisksAxis=ifrs-full_EquityPriceRiskMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_ConsolidatedAndSeparateFinancialStatementsAxis=cht_PreTaxProfitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_ConsolidatedAndSeparateFinancialStatementsAxis=cht_PreTaxOtherComprehensiveIncomeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |