Chunghwa Telecom Co Ltd. (SEC Filing Page | XBRL Cloud Viewer | XBRL Instance)

Line Label Object Class Period Type Balance Report ElementName
1 100000 - Document - Document and Entity Information Network

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 http://www.cht.com.tw/20181231/taxonomy/role/DocumentDocumentAndEntityInformation
2 Implied Table Table

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3 Documentand Entity Information [Abstract] Abstract cht:DocumentandEntityInformationAbstract
4 Document Type Concept (Submission Type) For Period dei:DocumentType
5 Amendment Flag Concept (Yes/No) For Period dei:AmendmentFlag
6 Document Period End Date Concept (Date) For Period dei:DocumentPeriodEndDate
7 Document Fiscal Year Focus Concept (Year) For Period dei:DocumentFiscalYearFocus
8 Document Fiscal Period Focus Concept (Fiscal Period) For Period dei:DocumentFiscalPeriodFocus
9 Trading Symbol Concept (Text/String) For Period dei:TradingSymbol
10 Entity Registrant Name Concept (Text/String) For Period dei:EntityRegistrantName
11 Entity Central Index Key Concept (CIK Number) For Period dei:EntityCentralIndexKey
12 Current Fiscal Year End Date Concept (Month/Day) For Period dei:CurrentFiscalYearEndDate
13 Entity Well-known Seasoned Issuer Concept (Yes/No) For Period dei:EntityWellKnownSeasonedIssuer
14 Entity Voluntary Filers Concept (Yes/No) For Period dei:EntityVoluntaryFilers
15 Entity Emerging Growth Company Concept (Yes/No) For Period dei:EntityEmergingGrowthCompany
16 Entity Shell Company Concept (Yes/No) For Period dei:EntityShellCompany
17 Entity Current Reporting Status Concept (Yes/No) For Period dei:EntityCurrentReportingStatus
18 Entity Filer Category Concept (Filer Category) For Period dei:EntityFilerCategory
19 Entity Common Stock, Shares Outstanding Concept (Shares) As Of dei:EntityCommonStockSharesOutstanding
20 100010 - Statement - Consolidated Balance Sheet Network

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 http://www.cht.com.tw/20181231/taxonomy/role/StatementConsolidatedBalanceSheet
21 Implied Table Table

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22 Statement Of Financial Position [Abstract] Abstract ifrs-full:StatementOfFinancialPositionAbstract
23 ASSETS Abstract ifrs-full:AssetsAbstract
24 CURRENT ASSETS Abstract ifrs-full:CurrentAssetsAbstract
25 Cash and cash equivalents Concept (Monetary) As Of Debit ifrs-full:CashAndCashEquivalents
26 Hedging financial assets Concept (Monetary) As Of Debit ifrs-full:HedgingInstrumentAssets
27 Contract assets Concept (Monetary) As Of Debit ifrs-full:CurrentContractAssets
28 Trade notes and accounts receivable, net Concept (Monetary) As Of Debit ifrs-full:CurrentTradeReceivables
29 Receivables from related parties Concept (Monetary) As Of Debit ifrs-full:TradeAndOtherCurrentReceivablesDueFromRelatedParties
30 Inventories Concept (Monetary) As Of Debit ifrs-full:Inventories
31 Prepayments Concept (Monetary) As Of Debit ifrs-full:CurrentPrepayments
32 Other current monetary assets Concept (Monetary) As Of Debit ifrs-full:OtherCurrentFinancialAssets
33 Other current assets Concept (Monetary) As Of Debit ifrs-full:OtherCurrentAssets
34 Total current assets Concept (Monetary) As Of Debit ifrs-full:CurrentAssets
35 NONCURRENT ASSETS Abstract ifrs-full:NoncurrentAssetsAbstract
36 Financial assets at fair value through profit or loss Concept (Monetary) As Of Debit ifrs-full:NoncurrentFinancialAssetsAtFairValueThroughProfitOrLoss
37 Financial assets at fair value through other comprehensive income Concept (Monetary) As Of Debit ifrs-full:NoncurrentFinancialAssetsAtFairValueThroughOtherComprehensiveIncome
38 Available-for-sale financial assets Concept (Monetary) As Of Debit ifrs-full:NoncurrentFinancialAssetsAvailableforsale
39 Investments accounted for using equity method Concept (Monetary) As Of Debit ifrs-full:InvestmentAccountedForUsingEquityMethod
40 Contract assets Concept (Monetary) As Of Debit ifrs-full:NoncurrentContractAssets
41 Property, plant and equipment Concept (Monetary) As Of Debit ifrs-full:PropertyPlantAndEquipment
42 Investment properties Concept (Monetary) As Of Debit ifrs-full:InvestmentProperty
43 Intangible assets Concept (Monetary) As Of Debit ifrs-full:IntangibleAssetsAndGoodwill
44 Deferred income tax assets Concept (Monetary) As Of Debit ifrs-full:DeferredTaxAssets
45 Incremental costs of obtaining a contract Concept (Monetary) As Of Debit ifrs-full:AssetsRecognisedFromCostsToObtainOrFulfilContractsWithCustomers
46 Net defined benefit assets Concept (Monetary) As Of Debit ifrs-full:NoncurrentRecognisedAssetsDefinedBenefitPlan
47 Prepayments Concept (Monetary) As Of Debit ifrs-full:NoncurrentPrepayments
48 Other noncurrent assets Concept (Monetary) As Of Debit ifrs-full:OtherNoncurrentAssets
49 Total noncurrent assets Concept (Monetary) As Of Debit ifrs-full:NoncurrentAssets
50 TOTAL Concept (Monetary) As Of Debit ifrs-full:Assets
51 LIABILITIES AND EQUITY Abstract ifrs-full:EquityAndLiabilitiesAbstract
52 CURRENT LIABILITIES Abstract ifrs-full:CurrentLiabilitiesAbstract
53 Short-term loans Concept (Monetary) As Of Credit ifrs-full:ShorttermBorrowings
54 Financial liabilities at fair value through profit or loss Concept (Monetary) As Of Credit ifrs-full:CurrentFinancialLiabilitiesAtFairValueThroughProfitOrLossClassifiedAsHeldForTrading
55 Hedging derivative financial liabilities Concept (Monetary) As Of Credit ifrs-full:CurrentDerivativeFinancialLiabilities
56 Contract liabilities Concept (Monetary) As Of Credit ifrs-full:CurrentContractLiabilities
57 Trade notes and accounts payable Concept (Monetary) As Of Credit ifrs-full:TradeAndOtherCurrentPayablesToTradeSuppliers
58 Payables to related parties Concept (Monetary) As Of Credit ifrs-full:TradeAndOtherCurrentPayablesToRelatedParties
59 Current tax liabilities Concept (Monetary) As Of Credit ifrs-full:CurrentTaxLiabilitiesCurrent
60 Other payables Concept (Monetary) As Of Credit ifrs-full:OtherCurrentPayables
61 Provisions Concept (Monetary) As Of Credit ifrs-full:CurrentProvisions
62 Advance receipts Concept (Monetary) As Of Credit ifrs-full:CurrentAdvances
63 Other current liabilities Concept (Monetary) As Of Credit ifrs-full:OtherCurrentLiabilities
64 Total current liabilities Concept (Monetary) As Of Credit ifrs-full:CurrentLiabilities
65 NONCURRENT LIABILITIES Abstract ifrs-full:NoncurrentLiabilitiesAbstract
66 Contract liabilities Concept (Monetary) As Of Credit ifrs-full:NoncurrentContractLiabilities
67 Long-term loans Concept (Monetary) As Of Credit ifrs-full:LongtermBorrowings
68 Deferred income tax liabilities Concept (Monetary) As Of Credit ifrs-full:DeferredTaxLiabilities
69 Provisions Concept (Monetary) As Of Credit ifrs-full:NoncurrentProvisions
70 Customers’ deposits Concept (Monetary) As Of Credit ifrs-full:NoncurrentDepositsFromCustomers
71 Net defined benefit liabilities Concept (Monetary) As Of Credit ifrs-full:NoncurrentRecognisedLiabilitiesDefinedBenefitPlan
72 Deferred revenue Concept (Monetary) As Of Credit ifrs-full:DeferredIncomeClassifiedAsNoncurrent
73 Other noncurrent liabilities Concept (Monetary) As Of Credit ifrs-full:OtherNoncurrentLiabilities
74 Total noncurrent liabilities Concept (Monetary) As Of Credit ifrs-full:NoncurrentLiabilities
75 Total liabilities Concept (Monetary) As Of Credit ifrs-full:Liabilities
76 EQUITY ATTRIBUTABLE TO STOCKHOLDERS OF THE PARENT Abstract ifrs-full:EquityAbstract
77 Common stocks Concept (Monetary) As Of Credit ifrs-full:IssuedCapital
78 Additional paid-in capital Concept (Monetary) As Of Credit ifrs-full:AdditionalPaidinCapital
79 Retained earnings Abstract cht:RetainedEarningsAbstract
80 Legal reserve Concept (Monetary) As Of Credit ifrs-full:StatutoryReserve
81 Special reserve Concept (Monetary) As Of Credit cht:SpecialReserve
82 Unappropriated earnings Concept (Monetary) As Of Credit cht:UnappropriatedRetainedEarnings
83 Total retained earnings Concept (Monetary) As Of Credit ifrs-full:RetainedEarnings
84 Other adjustments Concept (Monetary) As Of Credit ifrs-full:OtherReserves
85 Total equity attributable to stockholders of the parent Concept (Monetary) As Of Credit ifrs-full:EquityAttributableToOwnersOfParent
86 NONCONTROLLING INTERESTS Concept (Monetary) As Of Credit ifrs-full:NoncontrollingInterests
87 Total equity Concept (Monetary) As Of Credit ifrs-full:Equity
88 TOTAL Concept (Monetary) As Of Credit ifrs-full:EquityAndLiabilities
89 100020 - Statement - Consolidated Statements of Comprehensive Income Network

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 http://www.cht.com.tw/20181231/taxonomy/role/StatementConsolidatedStatementsOfComprehensiveIncome
90 Statements [Table] Table

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 cht:StatementsTable
91 Classes of share capital [axis] Axis ifrs-full:ClassesOfShareCapitalAxis
92 Share capital [member] Member ifrs-full:ClassesOfShareCapitalMember
93 American Depositary Shares [Member] Member cht:AmericanDepositarySharesMember
94 Statement [LineItems] LineItems cht:StatementsLineItems
95 REVENUES Concept (Monetary) For Period Credit ifrs-full:Revenue
96 OPERATING COSTS Concept (Monetary) For Period Debit ifrs-full:CostOfSales
97 GROSS PROFIT Concept (Monetary) For Period Credit ifrs-full:GrossProfit
98 OPERATING EXPENSES Abstract ifrs-full:MaterialIncomeAndExpenseAbstract
99 Marketing Concept (Monetary) For Period Debit ifrs-full:SalesAndMarketingExpense
100 General and administrative Concept (Monetary) For Period Debit ifrs-full:SellingGeneralAndAdministrativeExpense
101 Research and development Concept (Monetary) For Period Debit ifrs-full:ResearchAndDevelopmentExpense
102 Expected credit loss Concept (Monetary) For Period Debit cht:ExpectedCreditLoss
103 Total operating expenses Concept (Monetary) For Period Debit ifrs-full:OperatingExpenseExcludingCostOfSales
104 OTHER INCOME AND EXPENSES Concept (Monetary) For Period Credit ifrs-full:OtherOperatingIncomeExpense
105 INCOME FROM OPERATIONS Concept (Monetary) For Period Credit ifrs-full:ProfitLossFromOperatingActivities
106 NON-OPERATING INCOME AND EXPENSES Abstract cht:NonOperatingIncomeExpense1Abstract
107 Interest income Concept (Monetary) For Period Credit ifrs-full:RevenueFromInterest
108 Other income Concept (Monetary) For Period Credit cht:OtherNonOperatingIncome1
109 Other gains and losses Concept (Monetary) For Period Credit ifrs-full:OtherGainsLosses
110 Interest expenses Concept (Monetary) For Period Debit ifrs-full:InterestExpense
111 Share of the profits of associates and joint ventures accounted for using equity method Concept (Monetary) For Period Credit ifrs-full:ShareOfProfitLossOfAssociatesAndJointVenturesAccountedForUsingEquityMethod
112 Total non-operating income and expenses Concept (Monetary) For Period Credit cht:NonOperatingIncomeExpense1
113 INCOME BEFORE INCOME TAX Concept (Monetary) For Period Credit ifrs-full:ProfitLossBeforeTax
114 INCOME TAX EXPENSE Concept (Monetary) For Period Debit ifrs-full:IncomeTaxExpenseContinuingOperations
115 NET INCOME Concept (Monetary) For Period Credit ifrs-full:ProfitLoss
116 TOTAL OTHER COMPREHENSIVE INCOME (LOSS) Abstract ifrs-full:OtherComprehensiveIncomeAbstract
117 Items that will not be reclassified to profit or loss: Abstract ifrs-full:ComponentsOfOtherComprehensiveIncomeThatWillNotBeReclassifiedToProfitOrLossNetOfTaxAbstract
118 Remeasurements of defined benefit pension plans Concept (Monetary) For Period Credit ifrs-full:OtherComprehensiveIncomeBeforeTaxGainsLossesOnRemeasurementsOfDefinedBenefitPlans
119 Unrealized gain or loss on investments in equity instruments at fair value through other comprehensive income Concept (Monetary) For Period Credit cht:UnrealizedGainOrLossOnInvestmentsInEquityInstrumentsAtFairValueThroughOtherComprehensiveIncome
120 Gain or loss on hedging instruments subject to basis adjustment Concept (Monetary) For Period Credit ifrs-full:GainsLossesOnHedgingInstrument
121 Share of remeasurements of defined benefit pension plans of associates and joint ventures Concept (Monetary) For Period Credit ifrs-full:ShareOfOtherComprehensiveIncomeOfAssociatesAndJointVenturesAccountedForUsingEquityMethodThatWillNotBeReclassifiedToProfitOrLossBeforeTax
122 Income tax benefit relating to items that will not be reclassified to profit or loss Concept (Monetary) For Period Debit ifrs-full:IncomeTaxRelatingToComponentsOfOtherComprehensiveIncomeThatWillNotBeReclassifiedToProfitOrLoss
123 Items that will not be reclassified to profit or loss Concept (Monetary) For Period Credit ifrs-full:OtherComprehensiveIncomeThatWillNotBeReclassifiedToProfitOrLossNetOfTax
124 Items that may be reclassified subsequently to profit or loss: Abstract ifrs-full:ComponentsOfOtherComprehensiveIncomeThatWillBeReclassifiedToProfitOrLossNetOfTaxAbstract
125 Exchange differences arising from the translation of the foreign operations Concept (Monetary) For Period Credit ifrs-full:OtherComprehensiveIncomeBeforeTaxExchangeDifferencesOnTranslation
126 Unrealized gain or loss on available-for- sale financial assets Concept (Monetary) For Period Credit ifrs-full:OtherComprehensiveIncomeBeforeTaxAvailableforsaleFinancialAssets
127 Cash flow hedges Concept (Monetary) For Period Credit ifrs-full:OtherComprehensiveIncomeBeforeTaxCashFlowHedges
128 Share of exchange differences arising from the translation of the foreign operations of associates and joint ventures Concept (Monetary) For Period Credit ifrs-full:ShareOfOtherComprehensiveIncomeOfAssociatesAndJointVenturesAccountedForUsingEquityMethodThatWillBeReclassifiedToProfitOrLossBeforeTax
129 Income tax benefit relating to items that may be reclassified subsequently Concept (Monetary) For Period Debit ifrs-full:IncomeTaxRelatingToComponentsOfOtherComprehensiveIncomeThatWillBeReclassifiedToProfitOrLoss
130 Items that may be reclassified subsequently to profit or loss Concept (Monetary) For Period Credit ifrs-full:OtherComprehensiveIncomeThatWillBeReclassifiedToProfitOrLossNetOfTax
131 Total other comprehensive loss, net of income tax Concept (Monetary) For Period Credit ifrs-full:OtherComprehensiveIncome
132 TOTAL COMPREHENSIVE INCOME Concept (Monetary) For Period Credit ifrs-full:ComprehensiveIncome
133 NET INCOME ATTRIBUTABLE TO Abstract ifrs-full:ProfitLossAttributableToAbstract
134 Stockholders of the parent Concept (Monetary) For Period Credit ifrs-full:ProfitLossAttributableToOwnersOfParent
135 Noncontrolling interests Concept (Monetary) For Period Credit ifrs-full:ProfitLossAttributableToNoncontrollingInterests
136 NET INCOME Concept (Monetary) For Period Credit ifrs-full:ProfitLoss
137 COMPREHENSIVE INCOME ATTRIBUTABLE TO Abstract ifrs-full:ComprehensiveIncomeAttributableToAbstract
138 Stockholders of the parent Concept (Monetary) For Period Credit ifrs-full:ComprehensiveIncomeAttributableToOwnersOfParent
139 Noncontrolling interests Concept (Monetary) For Period Credit ifrs-full:ComprehensiveIncomeAttributableToNoncontrollingInterests
140 TOTAL COMPREHENSIVE INCOME Concept (Monetary) For Period Credit ifrs-full:ComprehensiveIncome
141 EARNINGS PER SHARE Abstract ifrs-full:EarningsPerShareAbstract
142 Basic Concept (Share) For Period ifrs-full:BasicEarningsLossPerShare
143 Diluted Concept (Share) For Period ifrs-full:DilutedEarningsLossPerShare
144 100040 - Statement - Consolidated Statements of Changes in Equity Network

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 http://www.cht.com.tw/20181231/taxonomy/role/StatementConsolidatedStatementsOfChangesInEquity
145 Statement Of Changes In Equity [Table] Table

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 ifrs-full:StatementOfChangesInEquityTable
146 Components of equity [axis] Axis ifrs-full:ComponentsOfEquityAxis
147 Equity [member] Member ifrs-full:EquityMember
148 Common stocks [Member] Member ifrs-full:IssuedCapitalMember
149 Additional paid-in capital [Member] Member ifrs-full:AdditionalPaidinCapitalMember
150 Legal reserve [Member] Member ifrs-full:StatutoryReserveMember
151 Special reserve [Member] Member cht:SpecialReserveMember
152 Unappropriated earnings [Member] Member cht:UnappropriatedEarningsMember
153 Total retained earnings [Member] Member ifrs-full:RetainedEarningsMember
154 Exchange differences arising from the translation of the foreign operations [Member] Member ifrs-full:ReserveOfExchangeDifferencesOnTranslationMember
155 Unrealized gain (loss) on available-for-sale financial assets [Member] Member ifrs-full:ReserveOfGainsAndLossesOnRemeasuringAvailableforsaleFinancialAssetsMember
156 Unrealized gain or loss on financial assets at fair value through other comprehensive income [Member] Member ifrs-full:ReserveOfGainsAndLossesOnFinancialAssetsMeasuredAtFairValueThroughOtherComprehensiveIncomeMember
157 Cash flow hedges [Member] Member ifrs-full:ReserveOfCashFlowHedgesMember
158 Gain or Loss on hedging instruments [Member] Member ifrs-full:ReserveOfGainsAndLossesOnHedgingInstrumentsThatHedgeInvestmentsInEquityInstrumentsMember
159 Total other adjustments [Member] Member ifrs-full:OtherReservesMember
160 Total equity attributable to stockholders of the parent [Member] Member ifrs-full:EquityAttributableToOwnersOfParentMember
161 Noncontrolling interests [Member] Member ifrs-full:NoncontrollingInterestsMember
162 Statement Of Changes In Equity [Line Items] LineItems ifrs-full:StatementOfChangesInEquityLineItems
163 Beginning balance Concept (Monetary) As Of Credit ifrs-full:Equity
164 Effect of retrospective application Concept (Monetary) As Of Credit cht:EffectOfRetrospectiveApplication
165 BALANCE AS ADJUSTED Concept (Monetary) As Of Credit cht:EquityAfterAdjustment
166 Provision for special reserve Concept (Monetary) For Period Credit cht:IncreaseDecreaseThroughTransferToSpecialReserve
167 Reversal of special reserve Concept (Monetary) For Period Debit cht:ReversalOfSpecialReserve
168 Cash dividends paid by Chunghwa Concept (Monetary) For Period Debit ifrs-full:DividendsPaid
169 Cash dividends distributed by subsidiaries Concept (Monetary) For Period Debit ifrs-full:DividendsRecognisedAsDistributionsToNoncontrollingInterests
170 Unclaimed dividend Concept (Monetary) For Period Credit cht:IncreaseDecreaseThroughUnclaimedDividend
171 Change in additional paid-in capital from investments in associates and joint ventures accounted for using equity method Concept (Monetary) For Period Credit cht:IncreaseDecreaseInAdditionalPaidinCapitalFromInvestmentsInAssociatesAndJointVenturesAccountedForUsingEquityMethod
172 Partial disposal of interests in subsidiaries Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseThroughDisposalOfSubsidiary
173 Change in additional paid-in capital for not participating proportionately in the capital increase of a subsidiary Concept (Monetary) For Period Credit cht:IncreaseDecreaseInAdditionalPaidinCapitalForNotParticipatingInCapitalIncreaseOfSubsidiary
174 Other changes in additional paid-in capital of subsidiaries Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseThroughTransfersAndOtherChangesEquity
175 Net income Concept (Monetary) For Period Credit ifrs-full:ProfitLoss
176 Total other comprehensive loss, net of income tax Concept (Monetary) For Period Credit ifrs-full:OtherComprehensiveIncome
177 TOTAL COMPREHENSIVE INCOME Concept (Monetary) For Period Credit ifrs-full:ComprehensiveIncome
178 Share-based payment transactions of subsidiaries Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseThroughSharebasedPaymentTransactions
179 Net increase in noncontrolling interests Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseThroughChangeInEquityOfSubsidiaries
180 Ending balance Concept (Monetary) As Of Credit ifrs-full:Equity
181 100050 - Statement - Consolidated Statements of Cash Flows Network

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 http://www.cht.com.tw/20181231/taxonomy/role/StatementConsolidatedStatementsOfCashFlows
182 Implied Table Table

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183 Statement Of Cash Flows [Abstract] Abstract ifrs-full:StatementOfCashFlowsAbstract
184 CASH FLOWS FROM OPERATING ACTIVITIES Abstract ifrs-full:CashFlowsFromUsedInOperatingActivitiesAbstract
185 Income before income tax Concept (Monetary) For Period Credit ifrs-full:ProfitLossBeforeTax
186 Adjustments to reconcile income before income tax to net cash provided by operating activities: Abstract ifrs-full:AdjustmentsForReconcileProfitLossAbstract
187 Depreciation Concept (Monetary) For Period Debit ifrs-full:DepreciationExpense
188 Amortization Concept (Monetary) For Period Debit ifrs-full:AmortisationExpense
189 Amortization of incremental costs of obtaining contracts Concept (Monetary) For Period Debit ifrs-full:AmortisationAssetsRecognisedFromCostsIncurredToObtainOrFulfilContractsWithCustomers
190 Expected credit loss Concept (Monetary) For Period Debit cht:ExpectedCreditLoss
191 Provision for doubtful accounts Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForImpairmentLossReversalOfImpairmentLossRecognisedInProfitOrLossTradeAndOtherReceivables
192 Interest expenses Concept (Monetary) For Period Debit ifrs-full:InterestExpense
193 Interest income Concept (Monetary) For Period Credit ifrs-full:RevenueFromInterest
194 Dividend income Concept (Monetary) For Period Credit ifrs-full:RevenueFromDividends
195 Compensation cost of share-based payment transactions Concept (Monetary) For Period Debit ifrs-full:ExpenseFromSharebasedPaymentTransactionsWithEmployees
196 Share of profits of associates and joint ventures accounted for using equity method Concept (Monetary) For Period Credit ifrs-full:ShareOfProfitLossOfAssociatesAndJointVenturesAccountedForUsingEquityMethod
197 Loss (gain) on disposal of property, plant and equipment Concept (Monetary) For Period Credit ifrs-full:GainsLossesOnDisposalsOfPropertyPlantAndEquipment
198 Property, plant and equipment transferred to expenses Concept (Monetary) For Period Debit cht:PropertyPlantAndEquipmentTransferredToExpenses
199 Loss on disposal of intangible assets Concept (Monetary) For Period Debit cht:LossOnDisposalOfIntangibleAssets
200 Gain on disposal of financial instruments Concept (Monetary) For Period Credit cht:GainLossesOnDisposalOfFinancialInstruments
201 Loss on disposal of investments accounted for using equity method Concept (Monetary) For Period Credit cht:GainLossOnDisposalOfInvestmentsAccountedForUsingEquityMethodNet
202 Impairment loss on available-for-sale financial assets Concept (Monetary) For Period Debit cht:ImpairmentLossReversalOfImpairmentLossRecognisedInProfitOrLossAvailableforsaleFinancialAssets
203 Provision for inventory and obsolescence Concept (Monetary) For Period ifrs-full:InventoryWritedown2011
204 Impairment loss on property, plant and equipment Concept (Monetary) For Period ifrs-full:ImpairmentLossRecognisedInProfitOrLossPropertyPlantAndEquipment
205 Reversal of impairment loss on investment properties Concept (Monetary) For Period ifrs-full:ReversalOfImpairmentLossRecognisedInProfitOrLossInvestmentProperty
206 Impairment loss on intangible assets Concept (Monetary) For Period ifrs-full:ImpairmentLossRecognisedInProfitOrLossIntangibleAssetsAndGoodwill
207 Valuation loss (gain) on financial assets and liabilities at fair value through profit or loss, net Concept (Monetary) For Period Credit cht:GainsLossesOnFinancialAssetsAndLiabilitiesAtFairValueThroughProfitOrLoss
208 Loss (gain) on foreign exchange, net Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForUnrealisedForeignExchangeLossesGains
209 Changes in operating assets and liabilities: Abstract cht:ChangeInOperatingAssetsAndLiabilitiesAbstract
210 Financial assets held for trading Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForDecreaseIncreaseInFinancialAssetsHeldForTrading
211 Financial assets mandatorily measured at fair value through profit or loss Concept (Monetary) For Period Credit ifrs-full:GainsLossesOnFinancialAssetsAtFairValueThroughProfitOrLossMandatorilyMeasuredAtFairValue
212 Contract assets Concept (Monetary) For Period Debit cht:AdjustmentsForDecreaseIncreaseInContractAssetsToReconcileProfitLossToNetCashFlowFromUsedInOperatingActivities
213 Trade notes and accounts receivable Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForDecreaseIncreaseInTradeAccountReceivable
214 Receivables from related parties Concept (Monetary) For Period Debit cht:AdjustmentsForDecreaseIncreaseInReceivablesFromRelatedParties
215 Inventories Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForDecreaseIncreaseInInventories
216 Prepayments Concept (Monetary) For Period Debit cht:AdjustmentsForDecreaseIncreaseInPrepayments
217 Other current monetary assets Concept (Monetary) For Period Debit cht:AdjustmentsForDecreaseIncreaseInOtherCurrentMonetaryAssets
218 Other current assets Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForDecreaseIncreaseInOtherCurrentAssets
219 Incremental cost of obtaining a contract Concept (Monetary) For Period Debit cht:IncrementalCostOfObtainingContract
220 Contract liabilities Concept (Monetary) For Period Debit cht:IncreaseDecreaseInContractLiabilities
221 Trade notes and accounts payable Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForIncreaseDecreaseInTradeAccountPayable
222 Payables to related parties Concept (Monetary) For Period Debit cht:AdjustmentsForIncreaseDecreaseInPayablesToRelatedParties
223 Other payables Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForIncreaseDecreaseInOtherOperatingPayables
224 Provisions Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForProvisions
225 Advance receipts Concept (Monetary) For Period Debit cht:AdjustmentsForIncreaseDecreaseInAdvanceReceipts
226 Other operating liabilities Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForIncreaseDecreaseInOtherLiabilities
227 Deferred revenue Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForIncreaseDecreaseInDeferredIncome
228 Net defined benefit plans Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForIncreaseDecreaseInEmployeeBenefitLiabilities
229 Cash generated from operations Concept (Monetary) For Period ifrs-full:CashFlowsFromUsedInOperations
230 Interest paid Concept (Monetary) For Period Credit ifrs-full:InterestPaidClassifiedAsOperatingActivities
231 Income tax paid Concept (Monetary) For Period Credit ifrs-full:IncomeTaxesPaidClassifiedAsOperatingActivities
232 Net cash provided by operating activities Concept (Monetary) For Period ifrs-full:CashFlowsFromUsedInOperatingActivities
233 CASH FLOWS FROM INVESTING ACTIVITIES Abstract ifrs-full:CashFlowsFromUsedInInvestingActivitiesAbstract
234 Acquisition of financial assets at fair value through other comprehensive income Concept (Monetary) For Period Debit cht:AcquisitionOfFinancialAssetsAtFairValueThroughOtherComprehensiveIncome
235 Proceeds from return of financial assets at fair value through other comprehensive income Concept (Monetary) For Period Debit cht:ProceedsFromReturnOfFinancialAssetsAtFairValueThroughOtherComprehensiveIncome
236 Acquisition of available-for-sale financial assets Concept (Monetary) For Period Credit ifrs-full:PurchaseOfAvailableforsaleFinancialAssets
237 Proceeds from disposal of available-for-sale financial assets Concept (Monetary) For Period Debit ifrs-full:ProceedsFromDisposalOrMaturityOfAvailableforsaleFinancialAssets
238 Proceeds from capital reduction of available-for-sale financial assets Concept (Monetary) For Period Debit cht:ProceedsFromReturnOfCapitalOfAvailableForSaleFinancialAssets
239 Acquisition of time deposits and negotiable certificate of deposit with maturities of more than three months Concept (Monetary) For Period Credit cht:PurchaseOfTimeDepositsAndNegotiableCertificateOfDeposit
240 Proceeds from disposal of time deposits and negotiable certificate of deposit with maturities of more than three months Concept (Monetary) For Period Debit cht:ProceedsFromDisposalOfTimeDepositsAndNegotiableCertificateOfDeposit
241 Proceeds from disposal of held-to-maturity financial assets Concept (Monetary) For Period Debit cht:ProceedsFromHeldToMaturityFinancialAssets
242 Acquisition of investments accounted for using equity method Concept (Monetary) For Period Credit ifrs-full:PurchaseOfInterestsInInvestmentsAccountedForUsingEquityMethod
243 Proceeds from disposal of investments accounted for using equity method Concept (Monetary) For Period Debit ifrs-full:ProceedsFromSalesOfInvestmentsAccountedForUsingEquityMethod
244 Proceeds from capital reduction of investments accounted for using equity method Concept (Monetary) For Period Debit cht:ProceedsFromCapitalReductionOfInvestmentsAccountedForUsingEquityMethod
245 Acquisition of property, plant and equipment Concept (Monetary) For Period Credit ifrs-full:PurchaseOfPropertyPlantAndEquipmentClassifiedAsInvestingActivities
246 Proceeds from disposal of property, plant and equipment Concept (Monetary) For Period Debit ifrs-full:ProceedsFromSalesOfPropertyPlantAndEquipmentClassifiedAsInvestingActivities
247 Acquisition of intangible assets Concept (Monetary) For Period Credit ifrs-full:PurchaseOfIntangibleAssetsClassifiedAsInvestingActivities
248 Acquisition of investment properties Concept (Monetary) For Period Credit ifrs-full:PurchaseOfInvestmentProperty
249 Increase in other noncurrent assets Concept (Monetary) For Period Debit cht:DecreaseIncreaseInOtherNonCurrentAssets
250 Interest received Concept (Monetary) For Period Debit ifrs-full:InterestReceivedClassifiedAsInvestingActivities
251 Cash dividends received Concept (Monetary) For Period Debit ifrs-full:DividendsReceivedClassifiedAsInvestingActivities
252 Net cash used in investing activities Concept (Monetary) For Period Debit ifrs-full:CashFlowsFromUsedInInvestingActivities
253 CASH FLOWS FROM FINANCING ACTIVITIES Abstract ifrs-full:CashFlowsFromUsedInFinancingActivitiesAbstract
254 Proceeds from short-term loans Concept (Monetary) For Period Debit ifrs-full:ProceedsFromCurrentBorrowings
255 Repayment of short-term loans Concept (Monetary) For Period Credit ifrs-full:RepaymentsOfCurrentBorrowings
256 Repayment of long-term loans Concept (Monetary) For Period Credit ifrs-full:RepaymentsOfNoncurrentBorrowings
257 Increase (decrease) in customers’ deposits Concept (Monetary) For Period Credit cht:IncreaseDecreaseInCustomersDeposits
258 Increase (decrease) in other noncurrent liabilities Concept (Monetary) For Period Debit cht:IncreaseDecreaseInOtherLiabilitiesNoncurrent
259 Cash dividends paid Concept (Monetary) For Period Credit ifrs-full:DividendsPaidClassifiedAsFinancingActivities
260 Partial disposal of interests in subsidiaries without losing control Concept (Monetary) For Period Debit ifrs-full:ProceedsFromChangesInOwnershipInterestsInSubsidiaries
261 Cash dividends distributed to noncontrolling interests Concept (Monetary) For Period Credit ifrs-full:DividendsPaidToNoncontrollingInterestsClassifiedAsFinancingActivities
262 Change in other noncontrolling interests Concept (Monetary) For Period Debit cht:ChangeInNoncontrollingInterestClassifiedAsFinancingActivities
263 Unclaimed dividend Concept (Monetary) For Period Credit cht:UnclaimedDividend
264 Net cash used in financing activities Concept (Monetary) For Period Debit ifrs-full:CashFlowsFromUsedInFinancingActivities
265 EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS Concept (Monetary) For Period Debit ifrs-full:EffectOfExchangeRateChangesOnCashAndCashEquivalents
266 NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS Concept (Monetary) For Period Debit ifrs-full:IncreaseDecreaseInCashAndCashEquivalents
267 CASH AND CASH EQUIVALENTS, BEGINNING OF THE YEAR Concept (Monetary) As Of Debit ifrs-full:CashAndCashEquivalents
268 CASH AND CASH EQUIVALENTS, END OF THE YEAR Concept (Monetary) As Of Debit ifrs-full:CashAndCashEquivalents
269 100060 - Disclosure - General Network

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270 Implied Table Table

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271 General Information [Abstract] Abstract cht:GeneralInformationAbstract
272 General Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfGeneralInformationAboutFinancialStatementsExplanatory
273 100070 - Disclosure - Approval of Financial Statements Network

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274 Implied Table Table

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275 Disclosure Of Approval Of Financial Statement [Abstract] Abstract cht:DisclosureOfApprovalOfFinancialStatementAbstract
276 Approval of Financial Statements Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfAuthorisationOfFinancialStatementsExplanatory
277 100080 - Disclosure - Summary of Significant Accounting Policies Network

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278 Implied Table Table

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279 Disclosure Of Summary Of Significant Accounting Policies [Abstract] Abstract cht:DisclosureOfSummaryOfSignificantAccountingPoliciesAbstract
280 Summary of Significant Accounting Policies Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfSummaryOfSignificantAccountingPoliciesExplanatory
281 100090 - Disclosure - Critical Accounting Judgments and Key Sources of Estimation, Uncertainty and Assumption Network

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282 Implied Table Table

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283 Disclosure Of Accounting Judgements And Estimates [Abstract] Abstract cht:DisclosureOfAccountingJudgementsAndEstimatesAbstract
284 Critical Accounting Judgments and Key Sources of Estimation, Uncertainty and Assumption Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfAccountingJudgementsAndEstimatesExplanatory
285 100100 - Disclosure - Application of New and Amended International Financial Reporting Standards Network

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286 Implied Table Table

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287 Description Of Expected Impact Of Initial Application Of New Standards Or Interpretations [Abstract] Abstract ifrs-full:DescriptionOfExpectedImpactOfInitialApplicationOfNewStandardsOrInterpretationsAbstract
288 Application of New and Amended International Financial Reporting Standards Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfExpectedImpactOfInitialApplicationOfNewStandardsOrInterpretations
289 100110 - Disclosure - U.S. Dollar Amounts Network

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290 Implied Table Table

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291 Foreign Exchange Rates [Abstract] Abstract ifrs-full:ForeignExchangeRatesAbstract
292 U.S. Dollar Amounts Concept (Text Block (HTML)) For Period cht:DisclosureOfConvenienceTranslationCurrencyExplanatory
293 100120 - Disclosure - Cash and Cash Equivalents Network

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294 Implied Table Table

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295 Cash And Cash Equivalents [Abstract] Abstract ifrs-full:CashAndCashEquivalentsAbstract
296 Cash and Cash Equivalents Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfCashAndCashEquivalentsExplanatory
297 100130 - Disclosure - Financial Instruments at Fair Value Through Profit or Loss Network

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298 Implied Table Table

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299 Disclosure Of Financial Instruments [Abstract] Abstract ifrs-full:DisclosureOfFinancialInstrumentsAbstract
300 Financial Instruments at Fair Value Through Profit or Loss Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfFinancialInstrumentsAtFairValueThroughProfitOrLossExplanatory
301 100140 - Disclosure - Financial Assets at Fair Value through Other Comprehensive Income Noncurrent Network

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302 Noncurrent Financial Assets At Fair Value Through Other Comprehensive Income [Table] Table

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303 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
304 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
305 Held-to-maturity financial assets [Member] Member ifrs-full:HeldtomaturityInvestmentsCategoryMember
306 Disclosure of financial assets [Line Items] LineItems cht:NoncurrentFinancialAssetsAtFairValueThroughOtherComprehensiveIncomeLineItems
307 Financial Assets at Fair Value through Other Comprehensive Income Noncurrent Concept (Text Block (HTML)) For Period cht:NoncurrentFinancialAssetsAtFairValueThroughOtherComprehensiveIncomeExplanatory
308 100150 - Disclosure - Available For Sale Financial Assets Noncurrent 2017 Network

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309 Statements [Table] Table

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310 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
311 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
312 Financial assets available-for-sale non current, category [Member] Member ifrs-full:FinancialAssetsAvailableforsaleCategoryMember
313 Statement [LineItems] LineItems cht:StatementsLineItems
314 Available-For-Sale Financial Assets-Noncurrent-2017 Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfFinancialAssetsExplanatory
315 100160 - Disclosure - Trade Notes and Accounts Receivable, Net Network

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316 Disclosure Of Financial Assets [Table] Table

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317 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
318 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
319 Trade notes and accounts receivable [Member] Member ifrs-full:TradeReceivablesMember
320 Disclosure Of Financial Assets [Line Items] LineItems ifrs-full:DisclosureOfFinancialAssetsLineItems
321 Trade Notes and Accounts Receivable, Net Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfTradeAndOtherReceivablesExplanatory
322 100170 - Disclosure - Inventories Network

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323 Implied Table Table

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324 Classes Of Inventories [Abstract] Abstract ifrs-full:ClassesOfInventoriesAbstract
325 Inventories Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfInventoriesExplanatory
326 100180 - Disclosure - Prepayments Network

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327 Implied Table Table

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328 Prepayments And Accrued Income [Abstract] Abstract ifrs-full:PrepaymentsAndAccruedIncomeAbstract
329 Prepayments Concept (Text Block (HTML)) For Period cht:DisclosureOfPrepaymentsExplanatory
330 100190 - Disclosure - Other Current Monetary Assets Network

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331 Implied Table Table

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332 Disclosure Of Other Current Monetary Assets [Abstract] Abstract cht:DisclosureOfOtherCurrentMonetaryAssetsAbstract
333 Other Current Monetary Assets Concept (Text Block (HTML)) For Period cht:DisclosureOfOtherCurrentMonetaryAssetsExplanatory
334 100200 - Disclosure - Subsidiaries Network

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335 Implied Table Table

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336 Disclosure Of Significant Investments In Subsidiaries [Abstract] Abstract ifrs-full:DisclosureOfSignificantInvestmentsInSubsidiariesAbstract
337 Subsidiaries Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfInterestsInSubsidiariesExplanatory
338 100210 - Disclosure - Investments Accounted for Using Equity Method Network

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339 Implied Table Table

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340 Disclosure Of Significant Investments In Associates And Joint Ventures [Abstract] Abstract cht:DisclosureOfSignificantInvestmentsInAssociatesAndJointVenturesAbstract
341 Investments Accounted for Using Equity Method Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfInvestmentsAccountedForUsingEquityMethodExplanatory
342 100220 - Disclosure - Property, Plant and Equipment Network

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343 Implied Table Table

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344 Disclosure Of Property Plant And Equipment [Abstract] Abstract ifrs-full:DisclosureOfPropertyPlantAndEquipmentAbstract
345 Property, Plant and Equipment Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfPropertyPlantAndEquipmentExplanatory
346 100230 - Disclosure - Investment Properties Network

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347 Implied Table Table

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348 Disclosure Of Investment Property [Abstract] Abstract ifrs-full:DisclosureOfInvestmentPropertyAbstract
349 Investment Properties Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfInvestmentPropertyExplanatory
350 100240 - Disclosure - Intangible Assets Network

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351 Implied Table Table

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352 Disclosure Of Intangible Assets [Abstract] Abstract ifrs-full:DisclosureOfIntangibleAssetsAbstract
353 Intangible Assets Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfIntangibleAssetsExplanatory
354 100250 - Disclosure - Other Assets Network

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355 Implied Table Table

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356 Miscellaneous Assets [Abstract] Abstract ifrs-full:MiscellaneousAssetsAbstract
357 Other Assets Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfOtherAssetsExplanatory
358 100260 - Disclosure - Hedging Derivative Financial Instruments Network

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359 Implied Table Table

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360 Disclosure Of Detailed Information About Hedging Instruments [Abstract] Abstract ifrs-full:DisclosureOfDetailedInformationAboutHedgingInstrumentsAbstract
361 Hedging Derivative Financial Instruments Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfDerivativeFinancialInstrumentsExplanatory
362 100270 - Disclosure - Short-Term Loans Network

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363 Disclosure Of Detailed Information About Borrowings [Table] Table

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364 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
365 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
366 Short-term loans [Member] Member cht:ShorttermLoansMember
367 Disclosure of detailed information about borrowings [Line Items] LineItems ifrs-full:DisclosureOfDetailedInformationAboutBorrowingsLineItems
368 Loans Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfBorrowingsExplanatory
369 100280 - Disclosure - Long-Term Loans Network

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370 Disclosure Of Detailed Information About Borrowings [Table] Table

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371 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
372 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
373 Long-term loans [Member] Member cht:LongTermLoansMember
374 Disclosure of detailed information about borrowings [Line Items] LineItems ifrs-full:DisclosureOfDetailedInformationAboutBorrowingsLineItems
375 Loans Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfBorrowingsExplanatory
376 100290 - Disclosure - Trade Notes and Accounts Payable Network

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377 Implied Table Table

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378 Trade And Other Current Payables [Abstract] Abstract ifrs-full:TradeAndOtherCurrentPayablesAbstract
379 Trade Notes and Accounts Payable Concept (Text Block (HTML)) For Period cht:DisclosureOfTradeNotesAndAccountsPayableExplanatory
380 100300 - Disclosure - Other Payables Network

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381 Implied Table Table

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382 Trade And Other Current Payables [Abstract] Abstract ifrs-full:TradeAndOtherCurrentPayablesAbstract
383 Other Payables Concept (Text Block (HTML)) For Period cht:DisclosureOfOtherPayablesExplanatory
384 100310 - Disclosure - Provisions Network

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385 Implied Table Table

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386 Provisions [Abstract] Abstract ifrs-full:ProvisionsAbstract
387 Provisions Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfProvisionsExplanatory
388 100320 - Disclosure - Advance Receipt – 2017 Network

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389 Implied Table Table

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390 Miscellaneous Current Liabilities [Abstract] Abstract ifrs-full:MiscellaneousCurrentLiabilitiesAbstract
391 Advance Receipt – 2017 Concept (Text Block (HTML)) For Period cht:DisclosureOfAdvanceReceiptExplanatory
392 100330 - Disclosure - Retirement Benefit Plans Network

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393 Implied Table Table

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394 Disclosure Of Retirement Benefit Plans [Abstract] Abstract cht:DisclosureOfRetirementBenefitPlansAbstract
395 Retirement Benefit Plans Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfEmployeeBenefitsExplanatory
396 100340 - Disclosure - Equity Network

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397 Implied Table Table

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398 Disclosure Of Classes Of Share Capital [Abstract] Abstract ifrs-full:DisclosureOfClassesOfShareCapitalAbstract
399 Equity Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfShareCapitalReservesAndOtherEquityInterestExplanatory
400 100350 - Disclosure - Revenue Network

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401 Implied Table Table

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402 Revenue From Rendering Of Telecommunication Services [Abstract] Abstract ifrs-full:RevenueFromRenderingOfTelecommunicationServicesAbstract
403 Revenue Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfRevenueExplanatory
404 100360 - Disclosure - Net Income and Other Comprehensive Income (Loss) Network

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405 Implied Table Table

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406 Analysis Of Income And Expense [Abstract] Abstract ifrs-full:AnalysisOfIncomeAndExpenseAbstract
407 Net Income and Other Comprehensive Income (Loss) Concept (Text Block (HTML)) For Period cht:DisclosureOfDetailedProfitOrLossAndOtherComprehensiveIncomeExplanatory
408 100370 - Disclosure - Income Tax Network

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409 Implied Table Table

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410 Major Components Of Tax Expense Income [Abstract] Abstract ifrs-full:MajorComponentsOfTaxExpenseIncomeAbstract
411 Income Tax Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfIncomeTaxExplanatory
412 100380 - Disclosure - Earnings Per Share Network

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413 Implied Table Table

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414 Earnings Per Share [Abstract] Abstract ifrs-full:EarningsPerShareAbstract
415 Earnings Per Share Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfEarningsPerShareExplanatory
416 100390 - Disclosure - Share-based Payment Arrangement Network

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417 Implied Table Table

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418 Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Abstract] Abstract ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementAbstract
419 Share-based Payment Arrangement Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfSharebasedPaymentArrangementsExplanatory
420 100400 - Disclosure - Non-cash Transactions Network

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421 Implied Table Table

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422 Noncash Investing Activities [Abstract] Abstract cht:NoncashInvestingActivitiesAbstract
423 Non Cash Transactions Concept (Text Block (HTML)) For Period cht:DisclosureOfNonCashTransactionsExplanatory
424 100410 - Disclosure - Operating Lease Arrangements Network

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425 Implied Table Table

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426 Disclosure Of Finance Lease And Operating Lease By Lessor [Abstract] Abstract ifrs-full:DisclosureOfFinanceLeaseAndOperatingLeaseByLessorAbstract
427 Operating Lease Arrangements Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfLeasesExplanatory
428 100420 - Disclosure - Capital Management Network

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429 Implied Table Table

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430 Capital Commitments [Abstract] Abstract ifrs-full:CapitalCommitmentsAbstract
431 Capital Management Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfObjectivesPoliciesAndProcessesForManagingCapitalExplanatory
432 100430 - Disclosure - Financial Instruments Network

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433 Implied Table Table

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434 Disclosure Of Financial Instruments [Abstract] Abstract ifrs-full:DisclosureOfFinancialInstrumentsAbstract
435 Financial Instruments Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfFinancialInstrumentsExplanatory
436 100440 - Disclosure - Fair Value Information Network

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437 Implied Table Table

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438 Disclosure Of Fair Value Measurement Of Financial Instruments [Abstract] Abstract cht:DisclosureOfFairValueMeasurementOfFinancialInstrumentsAbstract
439 Fair Value Information Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfFairValueMeasurementExplanatory
440 100450 - Disclosure - Related Parties Transactions Network

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441 Implied Table Table

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442 Related Party Transactions [Abstract] Abstract ifrs-full:RelatedPartyTransactionsAbstract
443 Related Parties Transactions Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfRelatedPartyExplanatory
444 100460 - Disclosure - Pledged Assets Network

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445 Implied Table Table

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446 Subclassifications Of Assets Liabilities And Equities [Abstract] Abstract ifrs-full:SubclassificationsOfAssetsLiabilitiesAndEquitiesAbstract
447 Pledged Assets Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfCollateralExplanatory
448 100470 - Disclosure - Significant Contingent Liabilities and Unrecognized Commitments Network

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449 Implied Table Table

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450 Commitments And Contingencies [Abstract] Abstract cht:CommitmentsAndContingenciesAbstract
451 Significant Contingent Liabilities and Unrecognized Commitments Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfCommitmentsAndContingentLiabilitiesExplanatory
452 100480 - Disclosure - Significant Subsequent Events Network

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453 Implied Table Table

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454 Disclosure Of Nonadjusting Events After Reporting Period [Abstract] Abstract ifrs-full:DisclosureOfNonadjustingEventsAfterReportingPeriodAbstract
455 Significant Subsequent Events Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfEventsAfterReportingPeriodExplanatory
456 100490 - Disclosure - Segment Information Network

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457 Implied Table Table

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458 Disclosure Of Operating Segments [Abstract] Abstract ifrs-full:DisclosureOfOperatingSegmentsAbstract
459 Segment Information Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfEntitysReportableSegmentsExplanatory
460 100500 - Disclosure - Summary of Significant Accounting Policies (Policies) Network

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461 Implied Table Table

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462 Disclosure Of Summary Of Significant Accounting Policies [Abstract] Abstract cht:DisclosureOfSummaryOfSignificantAccountingPoliciesAbstract
463 Statement of Compliance Concept (Text Block (HTML)) For Period ifrs-full:StatementOfIFRSCompliance
464 Basis of Preparation Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfBasisOfPreparationOfFinancialStatementsExplanatory
465 Current and Noncurrent Assets and Liabilities Concept (Text Block (HTML)) For Period cht:DescriptionOfAccountingPolicyForAssetAndLiabilityClassificationsExplanatory
466 Basis of Consolidation Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfBasisOfConsolidationExplanatory
467 Foreign Currencies Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForForeignCurrencyTranslationExplanatory
468 Cash Equivalents Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyToDetermineComponentsOfCashAndCashEquivalents
469 Inventories Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForMeasuringInventories
470 Buildings and Land Consigned to Construction Contractors Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForConstructionInProgressExplanatory
471 Investments in Associates and Joint Ventures Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForInvestmentInAssociatesAndJointVenturesExplanatory
472 Property, Plant and Equipment Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForPropertyPlantAndEquipmentExplanatory
473 Investment Properties Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForInvestmentPropertyExplanatory
474 Goodwill Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForGoodwillExplanatory
475 Intangible Assets Other Than Goodwill Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForIntangibleAssetsOtherThanGoodwillExplanatory
476 Impairment of Tangible Assets, Intangible Assets (Other Than Goodwill) and Incremental Costs of Obtaining Contracts Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForImpairmentOfAssetsExplanatory
477 Financial Instruments Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForFinancialInstrumentsExplanatory
478 Hedge Accounting Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForHedgingExplanatory
479 Provisions Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForProvisionsExplanatory
480 Revenue Recognition Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForRecognitionOfRevenue
481 Incremental costs of obtaining contracts Concept (Text Block (HTML)) For Period cht:DescriptionOfAccountingPolicyForIncrementalCostsOfObtainingContractsExplanatory
482 Leasing Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForLeasesExplanatory
483 Borrowing Costs Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForBorrowingCostsExplanatory
484 Employee Benefits Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForEmployeeBenefitsExplanatory
485 Share-based Payment Arrangements - Employee Stock Options Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForSharebasedPaymentTransactionsExplanatory
486 Income Tax Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForIncomeTaxExplanatory
487 100510 - Disclosure - Summary of Significant Accounting Policies (Tables) Network

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488 Implied Table Table

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489 Disclosure Of Significant Investments In Subsidiaries [Abstract] Abstract ifrs-full:DisclosureOfSignificantInvestmentsInSubsidiariesAbstract
490 Detail Information of Subsidiaries Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfSignificantInvestmentsInSubsidiariesExplanatory
491 100520 - Disclosure - Application of New and Amended International Financial Reporting Standards (Tables) Network

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492 Implied Table Table

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493 Description Of Expected Impact Of Initial Application Of New Standards Or Interpretations [Abstract] Abstract ifrs-full:DescriptionOfExpectedImpactOfInitialApplicationOfNewStandardsOrInterpretationsAbstract
494 Schedule of Original And New Measurement Categories and Carrying Amounts under IAS 39 and IFRS 9 Concept (Text Block (HTML)) For Period cht:DisclosureOfFinancialAssetsAndLiabilitiesAtDateOfInitialApplicationOfIFRS9Explanatory
495 Schedule of Anticipated Impacts on Assets, Liabilities and Equity from Retrospective Application of IFRS 15 Concept (Text Block (HTML)) For Period cht:DisclosureOfAnticipatedImpactOnItemsOfAssetsLiabilitiesAndEquityUponRetrospectiveApplicationOfIFRS15Explanatory
496 Summary of Increase (Decrease) in Assets, Liabilities and Equity Resulting from the Application of IFRS 15 On the Balance Sheet Date Concept (Text Block (HTML)) For Period cht:DisclosureOfAnticipatedImpactsOnAssetsLiabilitiesAndEquityOnBalanceSheetDateFromApplicationOfIFRS15Explanatory
497 Schedule of Increase (Decrease) in Net Income Resulting from the Application of IFRS 15 Concept (Text Block (HTML)) For Period cht:DisclosureOfAnticipatedImpactOnItemsOfStatementOfComprehensiveIncomeForCurrentYearFromApplicationOfIFRS15Explanatory
498 Schedule of Anticipated Impacts on Assets, Liabilities and Equity from Retrospective Application of IFRS 16 Concept (Text Block (HTML)) For Period cht:DisclosureOfAnticipatedImpactsOnAssetsLiabilitiesAndEquityWhenRetrospectivelyApplyingIFRS16Explanatory
499 100530 - Disclosure - Cash and Cash Equivalents (Tables) Network

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500 Implied Table Table

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501 Cash And Cash Equivalents [Abstract] Abstract ifrs-full:CashAndCashEquivalentsAbstract
502 Summary of Cash and Cash Equivalents Concept (Text Block (HTML)) For Period cht:DisclosureOfDetailedInformationAboutCashAndCashEquivalentsExplanatory
503 Annual Yield Rates of Bank Deposits, Commercial Paper, Negotiable Certificates of Deposit and Time Deposits Concept (Text Block (HTML)) For Period cht:ScheduleOfAnnualYieldRatesExplanatory
504 100540 - Disclosure - Financial Instruments at Fair Value Through Profit or Loss (Tables) Network

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 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureFinancialInstrumentsAtFairValueThroughProfitOrLossTables
505 Implied Table Table

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506 Disclosure Of Financial Instruments [Abstract] Abstract ifrs-full:DisclosureOfFinancialInstrumentsAbstract
507 Summary of Financial Instruments at Fair Value through Profit or Loss Concept (Text Block (HTML)) For Period cht:DisclosureOfDetailedInformationAboutFinancialInstrumentsAtFairValueThroughProfitOrLossExplanatory
508 Outstanding Forward Exchange Contracts Not Designated for Hedge Concept (Text Block (HTML)) For Period cht:DisclosureOfDetailedInformationOutstandingDerivativeContractsNotDesignatedForHedgeExplanatory
509 100550 - Disclosure - Financial Assets at Fair Value through Other Comprehensive Income Noncurrent (Tables) Network

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 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureFinancialAssetsAtFairValueThroughOtherComprehensiveIncomeNoncurrentTables
510 Implied Table Table

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511 Noncurrent Financial Assets At Fair Value Through Other Comprehensive Income [Abstract] Abstract ifrs-full:NoncurrentFinancialAssetsAtFairValueThroughOtherComprehensiveIncomeAbstract
512 Summary of Financial Assets at Fair Value through Other Comprehensive Income Noncurrent Concept (Text Block (HTML)) For Period cht:FinancialAssetsAtFairValueThroughOtherComprehensiveIncomeNoncurrentExplanatory
513 100560 - Disclosure - Available For Sale Financial Assets Noncurrent 2017 (Tables) Network

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514 Implied Table Table

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515 Disclosure Of Financial Assets [Abstract] Abstract ifrs-full:DisclosureOfFinancialAssetsAbstract
516 Summary of Available-for-sale Financial Assets Non Current Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfAvailableforsaleAssetsExplanatory
517 100570 - Disclosure - Trade Notes and Accounts Receivable, Net (Tables) Network

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518 Disclosure Of Financial Assets [Table] Table

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519 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
520 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
521 Trade notes and accounts receivable [Member] Member ifrs-full:TradeReceivablesMember
522 Disclosure Of Financial Assets [Line Items] LineItems ifrs-full:DisclosureOfFinancialAssetsLineItems
523 Summary of Trade Notes and Accounts Receivable, Net Concept (Text Block (HTML)) For Period cht:DisclosureOfTradeNotesAndAccountsReceivableNetExplanatory
524 Aging Analysis for Trade Notes and Accounts Receivable Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfFinancialAssetsThatAreEitherPastDueOrImpairedExplanatory
525 Receivables Past Due but Not Impaired Concept (Text Block (HTML)) For Period ifrs-full:AnalysisOfAgeOfFinancialAssetsThatArePastDueButNotImpaired
526 Movements of Allowance for Doubtful Accounts Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfAllowanceForCreditLossesExplanatory
527 Provision Matrix Arising from Telecommunications and Project Business Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfProvisionMatrixExplanatory
528 100580 - Disclosure - Inventories (Tables) Network

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529 Implied Table Table

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530 Classes Of Inventories [Abstract] Abstract ifrs-full:ClassesOfInventoriesAbstract
531 Summary of Inventories Concept (Text Block (HTML)) For Period cht:DisclosureOfDetailedInformationAboutInventoriesExplanatory
532 100590 - Disclosure - Prepayments (Tables) Network

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533 Implied Table Table

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534 Prepayments And Accrued Income [Abstract] Abstract ifrs-full:PrepaymentsAndAccruedIncomeAbstract
535 Summary of Prepayments Concept (Text Block (HTML)) For Period cht:DisclosureOfDetailedInformationAboutPrepaymentsExplanatory
536 100600 - Disclosure - Other Current Monetary Assets (Tables) Network

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537 Implied Table Table

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538 Disclosure Of Other Current Monetary Assets [Abstract] Abstract cht:DisclosureOfOtherCurrentMonetaryAssetsAbstract
539 Summary of Other Current Monetary Assets Concept (Text Block (HTML)) For Period cht:DisclosureOfDetailedInformationAboutOtherCurrentMonetaryAssetsExplanatory
540 Annual Yield Rates of Time Deposits and Negotiable Certificates of Deposits with Maturities of more Than Three Months Concept (Text Block (HTML)) For Period cht:DisclosureOfAnnualYieldRatesOfOtherCurrentMonetaryAssetsExplanatory
541 100610 - Disclosure - Subsidiaries (Tables) Network

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542 Disclosure Of Significant Investments In Subsidiaries [Table] Table

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543 Subsidiaries [axis] Axis ifrs-full:SignificantInvestmentsInSubsidiariesAxis
544 Entity's total for subsidiaries [member] Member ifrs-full:EntitysTotalForSubsidiariesMember
545 Less than wholly owned subsidiaries that have material noncontrolling interests [Member] Member ifrs-full:SubsidiariesWithMaterialNoncontrollingInterestsMember
546 Disclosure of subsidiaries [Line Items] LineItems ifrs-full:DisclosureOfSignificantInvestmentsInSubsidiariesLineItems
547 Detail Information of Subsidiaries Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfSignificantInvestmentsInSubsidiariesExplanatory
548 Summarized Financial Information Before Intercompany Eliminations Concept (Text Block (HTML)) For Period cht:DisclosureOfFinancialInformationBeforeIntercompanyEliminationsExplanatory
549 Detailed Information of Equity Transactions Concept (Text Block (HTML)) For Period cht:DisclosureOfDetailedInformationOfEquityTransactionsExplanatory
550 100620 - Disclosure - Investments Accounted for Using Equity Method (Tables) Network

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551 Implied Table Table

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552 Disclosure Of Significant Investments In Associates And Joint Ventures [Abstract] Abstract cht:DisclosureOfSignificantInvestmentsInAssociatesAndJointVenturesAbstract
553 Summary of Investments Accounted for Using Equity Method Concept (Text Block (HTML)) For Period cht:DisclosureOfDetailedInformationAboutInvestmentsAccountedForUsingEquityMethodExplanatory
554 Investments in Associates Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfSignificantInvestmentsInAssociatesExplanatory
555 Investments in Joint Ventures Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfJointVenturesExplanatory
556 100630 - Disclosure - Property, Plant and Equipment (Tables) Network

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557 Implied Table Table

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558 Disclosure Of Property Plant And Equipment [Abstract] Abstract ifrs-full:DisclosureOfPropertyPlantAndEquipmentAbstract
559 Summary of Property, Plant and Equipment Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfDetailedInformationAboutPropertyPlantAndEquipmentExplanatory
560 Disclosure Of Property Plant And Equipment Estimated Useful Life Explanatory Concept (Text Block (HTML)) For Period cht:DisclosureOfPropertyPlantAndEquipmentEstimatedUsefulLifeExplanatory
561 100640 - Disclosure - Investment Properties (Tables) Network

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562 Implied Table Table

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563 Disclosure Of Investment Property [Abstract] Abstract ifrs-full:DisclosureOfInvestmentPropertyAbstract
564 Summary of Investment Properties Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfDetailedInformationAboutInvestmentPropertyExplanatory
565 Estimated Service Lives of Investment Properties Concept (Text Block (HTML)) For Period cht:DisclosureOfInvestmentPropertyEstimatedUsefulLivesExplanatory
566 Key Assumptions and Fair Values of Investment Properties Concept (Text Block (HTML)) For Period cht:DisclosureOfKeyAssumptionsAndFairValuesOfInvestmentPropertiesExplanatory
567 100650 - Disclosure - Intangible Assets (Tables) Network

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568 Implied Table Table

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569 Disclosure Of Intangible Assets [Abstract] Abstract ifrs-full:DisclosureOfIntangibleAssetsAbstract
570 Summary of Intangible Assets Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfReconciliationOfChangesInIntangibleAssetsAndGoodwillExplanatory
571 100660 - Disclosure - Other Assets (Tables) Network

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572 Implied Table Table

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573 Miscellaneous Assets [Abstract] Abstract ifrs-full:MiscellaneousAssetsAbstract
574 Summary of Other Assets Concept (Text Block (HTML)) For Period cht:DisclosureOfDetailedInformationAboutOtherAssetsExplanatory
575 100670 - Disclosure - Hedging Derivative Financial Instruments (Tables) Network

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576 Disclosure Of Detailed Information About Hedging Instruments [Table] Table

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577 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
578 Risks [member] Member ifrs-full:TypesOfRisksMember
579 Foreign currency risk [Member] Member ifrs-full:CurrencyRiskMember
580 Disclosure Of Detailed Information About Hedging Instruments [Line Items] LineItems ifrs-full:DisclosureOfDetailedInformationAboutHedgingInstrumentsLineItems
581 Summary of Hedging Derivative Financial Instruments Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfDetailedInformationAboutHedgingInstrumentsExplanatory
582 Outstanding Forward Exchange Contracts Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfInformationAboutTermsAndConditionsOfHedgingInstrumentsAndHowTheyAffectFutureCashFlowsExplanatory
583 Loss (Gain) Arising from Hedging Derivative Financial Instruments that have been Reclassified from Equity to Initial Cost of the Property, Plant and Equipment Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfReclassificationOfFinancialInstrumentsExplanatory
584 Summary of Hedging Transaction and Reclassification Affected Comprehensive Income Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfReclassificationOfFinancialAssetsExplanatory
585 100680 - Disclosure - Short-Term Loans (Tables) Network

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586 Disclosure Of Detailed Information About Borrowings [Table] Table

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587 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
588 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
589 Short-term loans [Member] Member cht:ShorttermLoansMember
590 Disclosure of detailed information about borrowings [Line Items] LineItems ifrs-full:DisclosureOfDetailedInformationAboutBorrowingsLineItems
591 Summary of Loans Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfDetailedInformationAboutBorrowingsExplanatory
592 100690 - Disclosure - Long-Term Loans (Tables) Network

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593 Disclosure Of Detailed Information About Borrowings [Table] Table

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594 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
595 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
596 Long-term loans [Member] Member cht:LongTermLoansMember
597 Disclosure of detailed information about borrowings [Line Items] LineItems ifrs-full:DisclosureOfDetailedInformationAboutBorrowingsLineItems
598 Summary of Loans Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfDetailedInformationAboutBorrowingsExplanatory
599 100700 - Disclosure - Trade Notes and Accounts Payable (Tables) Network

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600 Implied Table Table

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601 Trade And Other Current Payables [Abstract] Abstract ifrs-full:TradeAndOtherCurrentPayablesAbstract
602 Summary of Trade Notes and Accounts Payable Concept (Text Block (HTML)) For Period cht:DisclosureDetailedInformationOfTradeNotesAndAccountsPayableExplanatory
603 100710 - Disclosure - Other Payables (Tables) Network

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604 Implied Table Table

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605 Trade And Other Current Payables [Abstract] Abstract ifrs-full:TradeAndOtherCurrentPayablesAbstract
606 Summary of Other Payables Concept (Text Block (HTML)) For Period cht:DisclosureOfDetailedInformationAboutOtherPayablesTextBlock
607 100720 - Disclosure - Provisions (Tables) Network

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608 Implied Table Table

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609 Provisions [Abstract] Abstract ifrs-full:ProvisionsAbstract
610 Summary of Provisions Concept (Text Block (HTML)) For Period cht:DisclosureOfDetailedInformationAboutProvisionsExplanatory
611 Movements in Provisions Concept (Text Block (HTML)) For Period cht:DisclosureOfMovementsInProvisionsExplanatory
612 100730 - Disclosure - Retirement Benefit Plans (Tables) Network

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613 Implied Table Table

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614 Disclosure Of Retirement Benefit Plans [Abstract] Abstract cht:DisclosureOfRetirementBenefitPlansAbstract
615 Amounts Included in Consolidated Balance Sheets from Obligation in Respect of Defined Benefit Plans Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfDefinedBenefitPlansExplanatory
616 Movements in Defined Benefit Obligation and Fair Value of Plan Assets Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetExplanatory
617 Pension Costs Recognized in Profit and Loss for Defined Benefit Plans Concept (Text Block (HTML)) For Period cht:DisclosureOfPensionCostsExplanatory
618 Principal Assumptions Used for Actuarial Valuations Concept (Text Block (HTML)) For Period cht:DisclosureOfPrincipalActuarialAssumptionsExplanatory
619 Effect on Present Value of Defined Benefit Obligation Due to a Reasonably Possible Change of the Significant Actuarial Assumptions Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfSensitivityAnalysisForActuarialAssumptionsExplanatory
620 Summary of Sensitivity Analysis Concept (Text Block (HTML)) For Period cht:SummaryOfExpectedContributionAndAverageDurationResultedSensitivityAnalysisExplanatory
621 Maturity Analysis of Undiscounted Benefit Payments Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfInformationAboutMaturityProfileOfDefinedBenefitObligationExplanatory
622 100740 - Disclosure - Equity (Tables) Network

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623 Disclosure Of Classes Of Share Capital [Table] Table

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624 Components of equity [axis] Axis ifrs-full:ComponentsOfEquityAxis
625 Equity [member] Member ifrs-full:EquityMember
626 Unrealized gain (loss) on available-for-sale financial assets [Member] Member ifrs-full:ReserveOfGainsAndLossesOnRemeasuringAvailableforsaleFinancialAssetsMember
627 Categories of financial assets [axis] Axis ifrs-full:CategoriesOfFinancialAssetsAxis
628 Financial assets, category [member] Member ifrs-full:FinancialAssetsCategoryMember
629 FVOCI [Member] Member ifrs-full:FinancialAssetsAtFairValueThroughOtherComprehensiveIncomeCategoryMember
630 Disclosure Of Classes Of Share Capital [Line Items] LineItems ifrs-full:DisclosureOfClassesOfShareCapitalLineItems
631 Summary of Common Stocks Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfClassesOfShareCapitalExplanatory
632 Adjustments of Additional Paid-in Capital Concept (Text Block (HTML)) For Period cht:DisclosureOfAdjustmentsToAdditionalPaidinCapitalExplanatory
633 Appropriations of Earnings Concept (Text Block (HTML)) For Period cht:DisclosureOfAppropriationOfRetainedEarningsExplanatory
634 Unrealized Gain or Loss on Available-for-sale Financial Assets Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfReservesAndOtherEquityInterestExplanatory
635 Unrealized Gain or Loss on Financial Assets at FVOCI Concept (Text Block (HTML)) For Period cht:DisclosureOfGainLossOnFinancialAssetsAtFVOCIExplanatory
636 Noncontrolling Interests Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfNoncontrollingInterestsExplanatory
637 100750 - Disclosure - Revenue (Tables) Network

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638 Implied Table Table

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639 Revenue [Abstract] Abstract ifrs-full:RevenueAbstract
640 Disclosure Of Detailed Information On Revenue Explanatory Concept (Text Block (HTML)) For Period cht:DisclosureOfDetailedInformationOnRevenueExplanatory
641 Summary of Disaggregation of Revenue Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfDisaggregationOfRevenueFromContractsWithCustomersExplanatory
642 Summary of Contract Balances Concept (Text Block (HTML)) For Period cht:DisclosureOfContractBalancesFromContractsWithCustomersExplanatory
643 Summary of Changes in Contract Assets and Contract Liabilities Concept (Text Block (HTML)) For Period ifrs-full:ExplanationOfSignificantChangesInContractAssetsAndContractLiabilitiesExplanatory
644 Summary of Revenue Recognized Concept (Text Block (HTML)) For Period cht:DisclosureOfRevenueRecognizedExplanatory
645 Summary of Incremental Costs of Obtaining Contracts Concept (Text Block (HTML)) For Period cht:DisclosureOfIncrementalCostExplanatory
646 100760 - Disclosure - Net Income and Other Comprehensive Income (Loss) (Tables) Network

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647 Implied Table Table

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648 Analysis Of Income And Expense [Abstract] Abstract ifrs-full:AnalysisOfIncomeAndExpenseAbstract
649 Other Income and Expenses Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfOtherOperatingIncomeExpenseExplanatory
650 Other Income Concept (Text Block (HTML)) For Period cht:DisclosureInDetailOfOtherIncomeExplanatory
651 Other Gains and Losses Concept (Text Block (HTML)) For Period cht:DisclosureOfOtherGainsAndLossesTextBlock
652 Impairment Loss (Reversal of Impairment Loss) on Financial Instruments and Non-financial Assets Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfImpairmentLossAndReversalOfImpairmentLossExplanatory
653 Depreciation and Amortization Expenses Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfDepreciationAndAmortisationExpenseExplanatory
654 Employee Benefit Expenses Concept (Text Block (HTML)) For Period cht:DisclosureOfEmployeeBenefitExpensesExplanatory
655 Reclassification Adjustments of Other Comprehensive Income (Loss) Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfAnalysisOfOtherComprehensiveIncomeByItemExplanatory
656 100770 - Disclosure - Income Tax (Tables) Network

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657 Implied Table Table

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658 Major Components Of Tax Expense Income [Abstract] Abstract ifrs-full:MajorComponentsOfTaxExpenseIncomeAbstract
659 Major Components of Income Tax Expense Concept (Text Block (HTML)) For Period cht:ComponentsOfIncomeTaxExpenseExplanatory
660 Reconciliation of Accounting Profit and Income Tax Expense Concept (Text Block (HTML)) For Period cht:ReconciliationOfAccountingProfitAndIncomeTaxExpenseExplanatory
661 Income Tax Benefit Recognized in Other Comprehensive Income Concept (Text Block (HTML)) For Period cht:DisclosureOfIncomeTaxExpenseBenefitRecognizedInOtherComprehensiveIncomeExplanatory
662 Current Tax Assets and Liabilities Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfTaxReceivablesAndPayablesExplanatory
663 Movements of Deferred Income Tax Assets and Liabilities Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfDeferredTaxesExplanatory
664 Items for Which No Deferred Income Tax Assets Have Been Recognized Concept (Text Block (HTML)) For Period cht:DisclosureOfDeferredIncomeTaxAssetNotRecognizedExplanatory
665 Information About Unused Loss Carryforwards Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfTemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsExplanatory
666 100780 - Disclosure - Earnings Per Share (Tables) Network

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667 Implied Table Table

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668 Earnings Per Share [Abstract] Abstract ifrs-full:EarningsPerShareAbstract
669 Net Income and Weighted Average Number of Common Stocks Used in Calculation of Earnings Per Share Concept (Text Block (HTML)) For Period ifrs-full:EarningsPerShareExplanatory
670 100790 - Disclosure - Share-based Payment Arrangement (Tables) Network

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671 Statements [Table] Table

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672 Subsidiaries [axis] Axis ifrs-full:SignificantInvestmentsInSubsidiariesAxis
673 Entity's total for subsidiaries [member] Member ifrs-full:EntitysTotalForSubsidiariesMember
674 Senao International Co., Ltd. (SENAO) [Member] Member cht:SenaoInternationalCoLtdMember
675 CHIEF Telecom Inc. (CHIEF) [Member] Member cht:CHIEFTelecomIncMember
676 Chunghwa Precision Test Tech. Co., Ltd. (CHPT) [Member] Member cht:ChunghwaPrecisionTestTechCoLtdMember
677 Statement [LineItems] LineItems cht:StatementsLineItems
678 Share-based Compensation Plan Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementExplanatory
679 Outstanding Stock Options Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfNumberAndWeightedAverageExercisePricesOfShareOptionsExplanatory
680 Employee Stock Options Outstanding Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfNumberAndWeightedAverageRemainingContractualLifeOfOutstandingShareOptionsExplanatory
681 100790 - Disclosure - Share-based Payment Arrangement (Tables) Network

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682 Implied Table Table

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683 Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Abstract] Abstract ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementAbstract
684 Assumptions used to Evaluate Options and Fair Value of Options Concept (Text Block (HTML)) For Period cht:DisclosureOfSignificantAssumptionsUsedToEstimateFairValueOfOptionsGrantedExplanatory
685 100800 - Disclosure - Non-cash Transactions (Tables) Network

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686 Implied Table Table

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687 Noncash Investing Activities [Abstract] Abstract cht:NoncashInvestingActivitiesAbstract
688 Non-cash Investing Activities Concept (Text Block (HTML)) For Period cht:DisclosureOfNonCashInvestingTransactionsExplanatory
689 100810 - Disclosure - Operating Lease Arrangements (Tables) Network

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690 Implied Table Table

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691 Disclosure Of Finance Lease And Operating Lease By Lessor [Abstract] Abstract ifrs-full:DisclosureOfFinanceLeaseAndOperatingLeaseByLessorAbstract
692 Future Aggregate Minimum Lease Payments Under Non-cancellable Operating Leases Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfFinanceLeaseAndOperatingLeaseByLesseeExplanatory
693 Future Aggregate Minimum Lease Collection Under Non-cancellable Operating Leases Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfFinanceLeaseAndOperatingLeaseByLessorExplanatory
694 100820 - Disclosure - Financial Instruments (Tables) Network

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695 Disclosure Of Financial Instruments [Table] Table

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696 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
697 Risks [member] Member ifrs-full:TypesOfRisksMember
698 Foreign currency risk [Member] Member ifrs-full:CurrencyRiskMember
699 Interest rate risk [member] Member ifrs-full:InterestRateRiskMember
700 Disclosure of detailed information about financial instruments [Line Items] LineItems ifrs-full:DisclosureOfFinancialInstrumentsLineItems
701 Summary of Categories of Financial Instruments Concept (Text Block (HTML)) For Period cht:DisclosureOfCategoriesOfFinancialInstrumentsExplanatory
702 Carrying Amounts of Assets and Liabilities Related to Market Risk Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfNatureAndExtentOfRisksArisingFromFinancialInstrumentsExplanatory
703 Foreign Currency Risk Sensitivity Analysis Concept (Text Block (HTML)) For Period cht:DisclosureOfSensitivityAnalysisExplanatory
704 Maturity Analysis For Nonderivative Financial Liabilities Concept (Text Block (HTML)) For Period ifrs-full:MaturityAnalysisForNonderivativeFinancialLiabilities
705 Liquidity Analysis for Derivative Financial Instruments Concept (Text Block (HTML)) For Period ifrs-full:MaturityAnalysisForDerivativeFinancialLiabilities
706 Financing Facilities Concept (Text Block (HTML)) For Period cht:FinancingFacilitiesExplanatory
707 100830 - Disclosure - Related Parties Transactions (Tables) Network

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708 Implied Table Table

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709 Related Party Transactions [Abstract] Abstract ifrs-full:RelatedPartyTransactionsAbstract
710 Summary of Related Parties Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfTransactionsBetweenRelatedPartiesExplanatory
711 Compensation of Directors and Other Key Management Personnel Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfInformationAboutKeyManagementPersonnelExplanatory
712 100840 - Disclosure - Pledged Assets (Tables) Network

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713 Implied Table Table

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714 Subclassifications Of Assets Liabilities And Equities [Abstract] Abstract ifrs-full:SubclassificationsOfAssetsLiabilitiesAndEquitiesAbstract
715 Assets Pledged as Collaterals Concept (Text Block (HTML)) For Period cht:DisclosureOfDetailedInformationAboutCollateralExplanatory
716 100850 - Disclosure - Segment Information (Tables) Network

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717 Implied Table Table

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718 Disclosure Of Operating Segments [Abstract] Abstract ifrs-full:DisclosureOfOperatingSegmentsAbstract
719 Analysis by Reportable Segment of Revenue and Operating Results of Continuing Operations Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfOperatingSegmentsExplanatory
720 Other Segment Information Concept (Text Block (HTML)) For Period cht:DisclosureOfOtherSegmentalInformationExplanatory
721 Main Products and Service Revenues Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfProductsAndServicesExplanatory
722 Geographic Information Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfGeographicalAreasExplanatory
723 100860 - Disclosure - General - Additional Information (Detail) Network

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724 Implied Table Table

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725 General Information [Abstract] Abstract cht:GeneralInformationAbstract
726 Description of percentage of ownership interes Concept (Text/String) For Period cht:DescriptionOfPercentageOfPortionOfOwnershipInterest
727 100870 - Disclosure - Summary of Significant Accounting Policies - Detail Information of Subsidiaries (Detail) Network

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728 Disclosure Of Significant Investments In Subsidiaries [Table] Table

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729 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
730 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
731 Chunghwa Telecom Co., Ltd. [Member] Member cht:ChunghwaTelecomCoLtdMember
732 Senao International Co., Ltd. (SENAO) [Member] Member cht:SenaoInternationalCoLtdMember
733 Youth Co., Ltd. (Youth) [Member] Member cht:YouthCoLtdMember
734 CHIEF Telecom Inc. (CHIEF) [Member] Member cht:CHIEFTelecomIncMember
735 Light Era Development Co., Ltd. (LED) [Member] Member cht:LightEraDevelopmentCoLtdMember
736 Chunghwa System Integration Co., Ltd. (CHSI) [Member] Member cht:ChunghwaSystemIntegrationCoLtdMember
737 Chunghwa Investment Co., Ltd. (CHI) [Member] Member cht:ChunghwaInvestmentCoLtdMember
738 Concord Technology Co., Ltd. (Concord) [Member] Member cht:ConcordTechnologyCoLtdMember
739 Chunghwa Precision Test Tech. Co., Ltd. (CHPT) [Member] Member cht:ChunghwaPrecisionTestTechCoLtdMember
740 Senao International (Samoa) Holding Ltd. (SIS) [Member] Member cht:SenaoInternationalSamoaHoldingLtdMember
741 Prime Asia Investments Group Ltd. (B.V.I.) (Prime Asia) [Member] Member cht:PrimeAsiaInvestmentsGroupLtdMember
742 Senao International HK Limited (SIHK) [Member] Member cht:SenaoInternationalHKLimitedMember
743 Chunghwa Hsingta Co., Ltd. ("CHC") [Member] Member cht:ChunghwaHsingtaCoLtdMember
744 Chunghwa Precision Test Tech. International Ltd. ("CHPT (International)") [Member] Member cht:ChunghwaPrecisionTestTechInternationalLtdMember
745 Subsidiaries [axis] Axis ifrs-full:SignificantInvestmentsInSubsidiariesAxis
746 Entity's total for subsidiaries [member] Member ifrs-full:EntitysTotalForSubsidiariesMember
747 Senao International Co., Ltd. (SENAO) [Member] Member cht:SenaoInternationalCoLtdMember
748 Light Era Development Co., Ltd. (LED) [Member] Member cht:LightEraDevelopmentCoLtdMember
749 Donghwa Telecom Co., Ltd. (DHT) [Member] Member cht:DonghwaTelecomCoLtdMember
750 Chunghwa Telecom Singapore Pte., Ltd. (CHTS) [Member] Member cht:ChunghwaTelecomSingaporePteLtdMember
751 Chunghwa System Integration Co., Ltd. (CHSI) [Member] Member cht:ChunghwaSystemIntegrationCoLtdMember
752 Chunghwa Investment Co., Ltd. (CHI) [Member] Member cht:ChunghwaInvestmentCoLtdMember
753 CHIEF Telecom Inc. (CHIEF) [Member] Member cht:CHIEFTelecomIncMember
754 CHYP Multimedia Marketing & Communications Co., Ltd. (?CHYP?) [Member] Member cht:CHYPMultimediaMarketingAndCommunicationsCoLtdMember
755 Prime Asia Investments Group Ltd. (B.V.I.) (Prime Asia) [Member] Member cht:PrimeAsiaInvestmentsGroupLtdMember
756 Spring House Entertainment Tech. Inc. (SHE) [Member] Member cht:SpringHouseEntertainmentTechIncMember
757 Chunghwa Telecom Global, Inc. ("CHTG") [Member] Member cht:ChunghwaTelecomGlobalIncMember
758 Chunghwa Telecom Vietnam Co., Ltd. (CHTV) [Member] Member cht:ChunghwaTelecomVietnamCoLtdMember
759 Smartfun Digital Co., Ltd. (SFD) [Member] Member cht:SmartfunDigitalCoLtdMember
760 Chunghwa Telecom Japan Co., Ltd. (CHTJ) [Member] Member cht:ChunghwaTelecomJapanCoLtdMember
761 Chunghwa Sochamp Technology Inc. (CHST) [Member] Member cht:ChunghwaSochampTechnologyIncMember
762 Honghwa International Co., Ltd. (HHI) [Member] Member cht:HonghwaInternationalCoLtdMember
763 Chunghwa Leading Photonics Tech Co., Ltd. (CLPT) [Member] Member cht:ChunghwaLeadingPhotonicsTechCoMember
764 Chunghwa Telecom (Thailand) Co., Ltd. ("CHTT") [Member] Member cht:ChunghwaTelecomThailandCoLtdMember
765 Senao International (Samoa) Holding Ltd. (SIS) [Member] Member cht:SenaoInternationalSamoaHoldingLtdSISMember
766 New Prospect Investments Holdings Ltd. (B.V.I.) (New Prospect) [Member] Member cht:NewProspectInvestmentsHoldingsLtdMember
767 Youth Co., Ltd. (Youth) [Member] Member cht:YouthCoLtdYouthMember
768 Aval Technologies Co., Ltd. (Aval) [Member] Member cht:AvaltechnologiescoltdMember
769 ISPOT Co., Ltd. (ISPOT) [Member] Member cht:ISPOTCoLtdMember
770 Youyi Co., Ltd. (Youyi) [Member] Member cht:YouyiCoLtdMember
771 SENYOUNG Insurance Agent Co., Ltd. [Member] Member cht:SENYOUNGInsuranceAgentCoLtdMember
772 Unigate Telecom Inc. (Unigate) [Member] Member cht:UnigateTelecomIncMember
773 Chief International Corp. (CIC) [Member] Member cht:ChiefInternationalCorpMember
774 Shanghai Chief Telecom Co., Ltd. (SCT) [Member] Member cht:ShanghaiChiefTelecomCoLtdMember
775 Taoyuan Asia Silicon Valley Innovation Co., Ltd [Member] Member cht:TaoyuanAsiaSiliconValleyInnovationCoLtdMember
776 Concord Technology Co., Ltd. (Concord) [Member] Member cht:ConcordTechnologyCoLtdConcordMember
777 Chunghwa Precision Test Tech. Co., Ltd. (CHPT) [Member] Member cht:ChunghwaPrecisionTestTechCoLtdCHPTMember
778 Glory Network System Service (Shanghai) Co., Ltd. (GNSS (Shanghai) [Member] Member cht:GloryNetworkSystemServiceShanghaiCoLtdMember
779 Chunghwa Precision Test Tech. USA Corporation (CHPT (US) [Member] Member cht:ChunghwaPrecisionTestTechUSACorporationMember
780 CHPT Japan Co., Ltd. (CHPT (JP) [Member] Member cht:CHPTJapanCoLtdMember
781 Chunghwa Precision Test Tech. International Ltd. ("CHPT (International)") [Member] Member cht:ChunghwaPrecisionTestTechInternationalLtdMember
782 Senao International HK Limited (SIHK) [Member] Member cht:SenaoInternationalHKLimitedSIHKMember
783 Chunghwa Telecom Security Co Ltd [Member] Member cht:ChunghwaTelecomSecurityCoLtdMember
784 Chunghwa Hsingta Co., Ltd. ("CHC") [Member] Member cht:ChunghwaHsingtaCoLtdCHCMember
785 Senao Trading (Fujian) Co., Ltd. (STF) [Member] Member cht:SenaoTradingFujianCoLtdMember
786 Chunghwa Telecom (China) Co., Ltd. ("CTC") [Member] Member cht:ChunghwaTelecomChinaCoLtdMember
787 Senao International Trading (Shanghai) Co., Ltd. (SITS) [Member] Member cht:SenaoInternationalTradingShanghaiCoLtdSITSMember
788 Jiangsu Zhenhua Information Technology Company, LLC. ("JZIT") [Member] Member cht:JiangsuZhenhuaInformationTechnologyCompanyLlcMember
789 Senao International Trading (Shanghai) Co Ltd (SEITS) [Member] Member cht:SenaoInternationalTradingShanghaiCoLtdSEITSMember
790 Shanghai Taihua Electronic Technology Limited ("STET") [Member] Member cht:ShanghaiTaihuaElectronicTechnologyLimitedMember
791 Senao International Trading (Jiangsu) Co., Ltd. (SITJ) [Member] Member cht:SenaoInternationalTradingJiangsuCoLtdMember
792 Disclosure of subsidiaries [Line Items] LineItems ifrs-full:DisclosureOfSignificantInvestmentsInSubsidiariesLineItems
793 Main Businesses and Products Concept (Text/String) For Period ifrs-full:DescriptionOfNatureOfEntitysOperationsAndPrincipalActivities
794 Percentage of Ownership Concept (Percent) As Of cht:PercentageOfOwnershipInterestInSubsidiary
795 100880 - Disclosure - Summary of Significant Accounting Policies - Detail Information of Subsidiaries (Parenthetical) (Detail) Network

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796 Disclosure Of Significant Investments In Subsidiaries [Table] Table

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 ifrs-full:DisclosureOfSignificantInvestmentsInSubsidiariesTable
797 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
798 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
799 Chunghwa Telecom Co., Ltd. [Member] Member cht:ChunghwaTelecomCoLtdMember
800 Youth Co., Ltd. (Youth) [Member] Member cht:YouthCoLtdMember
801 Senao International Co., Ltd. (SENAO) [Member] Member cht:SenaoInternationalCoLtdMember
802 Light Era Development Co., Ltd. (LED) [Member] Member cht:LightEraDevelopmentCoLtdMember
803 Chunghwa Investment Co., Ltd. (CHI) [Member] Member cht:ChunghwaInvestmentCoLtdMember
804 Subsidiaries [axis] Axis ifrs-full:SignificantInvestmentsInSubsidiariesAxis
805 Entity's total for subsidiaries [member] Member ifrs-full:EntitysTotalForSubsidiariesMember
806 Senao International Co., Ltd. (SENAO) [Member] Member cht:SenaoInternationalCoLtdMember
807 CHIEF Telecom Inc. (CHIEF) [Member] Member cht:CHIEFTelecomIncMember
808 Chunghwa Telecom (Thailand) Co., Ltd. ("CHTT") [Member] Member cht:ChunghwaTelecomThailandCoLtdMember
809 Chunghwa Telecom Security Co Ltd [Member] Member cht:ChunghwaTelecomSecurityCoLtdMember
810 SENYOUNG Insurance Agent Co., Ltd. [Member] Member cht:SENYOUNGInsuranceAgentCoLtdMember
811 Taoyuan Asia Silicon Valley Innovation Co., Ltd [Member] Member cht:TaoyuanAsiaSiliconValleyInnovationCoLtdMember
812 Chunghwa Precision Test Tech. Co., Ltd. (CHPT) [Member] Member cht:ChunghwaPrecisionTestTechCoLtdMember
813 Range [axis] Axis ifrs-full:RangeAxis
814 Ranges [member] Member ifrs-full:RangesMember
815 Bottom of Range [Member] Member ifrs-full:BottomOfRangeMember
816 Top of Range [Member] Member ifrs-full:TopOfRangeMember
817 Disclosure of subsidiaries [Line Items] LineItems ifrs-full:DisclosureOfSignificantInvestmentsInSubsidiariesLineItems
818 Percentage of Ownership Concept (Percent) As Of cht:PercentageOfOwnershipInterestInSubsidiary
819 100890 - Disclosure - Summary of Significant Accounting Policies - Additional information (Detail) Network

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820 Disclosure Of Significant Investments In Subsidiaries [Table] Table

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821 Legal Entity Axis dei:LegalEntityAxis
822 Entity Member dei:EntityDomain
823 Chunghwa Investment Co., Ltd. (CHI) [Member] Member cht:ChunghwaInvestmentCoLtdMember
824 Subsidiaries [axis] Axis ifrs-full:SignificantInvestmentsInSubsidiariesAxis
825 Entity's total for subsidiaries [member] Member ifrs-full:EntitysTotalForSubsidiariesMember
826 CHIEF Telecom Inc. (CHIEF) [Member] Member cht:CHIEFTelecomIncMember
827 Senao International Co., Ltd. (SENAO) [Member] Member cht:SenaoInternationalCoLtdMember
828 Disclosure of subsidiaries [Line Items] LineItems ifrs-full:DisclosureOfSignificantInvestmentsInSubsidiariesLineItems
829 Percentage of Ownership Concept (Percent) As Of cht:PercentageOfOwnershipInterestInSubsidiary
830 100900 - Disclosure - Application of New and Amended International Financial Reporting Standards - Schedule of Original And New Measurement Categories and Carrying Amounts under IAS 39 and IFRS 9 (Details) Network

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831 Disclosure Of Initial Application Of Standards Or Interpretations [Table] Table

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 ifrs-full:DisclosureOfInitialApplicationOfStandardsOrInterpretationsTable
832 Classes of financial liabilities [axis] Axis ifrs-full:ClassesOfFinancialLiabilitiesAxis
833 Financial liabilities, class [member] Member ifrs-full:FinancialLiabilitiesMember
834 Short-term loans, trade notes and accounts payable, payables to related parties, partial other payables, customers’ deposit and loan-term loans Member cht:ShortTermLoansTradeNotesAndAccountsPayablePayablesToRelatedPartiesPartialOtherPayablesCustomersDepositAndLoanTermLoansMember
835 Derivatives [Member] Member ifrs-full:DerivativesMember
836 Hedging Derivative Financial Liabilities [Member] Member cht:HedgingDerivativeFinancialLiabilitiesMember
837 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
838 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
839 Cash and Cash Equivalents [Member] Member cht:CashAndCashEquivalentMember
840 Equity Securities I [Member] Member us-gaap:EquitySecuritiesMember
841 Equity Securities II [Member] Member ifrs-full:EquityInvestmentsMember
842 Trade Notes and Accounts Receivable, Receivables from Related Parties, Other Current Monetary Assets and Refundable Deposits [Member] Member cht:TradeNotesAndAccountsReceivableReceivablesFromRelatedPartiesOtherCurrentMonetaryAssetsAndRefundableDepositsMember
843 Accounting estimates [axis] Axis ifrs-full:AccountingEstimatesAxis
844 Accounting estimates [member] Member ifrs-full:AccountingEstimatesMember
845 Reclassifications [Member] Member cht:ReclassificationsMember
846 Remeasurements [Member] Member cht:RemeasurementsMember
847 Other Adjustment [Member] Member cht:OtherAdjustmentMember
848 Initially applied IFRSs [axis] Axis ifrs-full:InitiallyAppliedIFRSsAxis
849 Initially applied IFRSs [member] Member ifrs-full:InitiallyAppliedIFRSsMember
850 IAS 39 [Member] Member cht:IAS39Member
851 IFRS 9 [Member] Member cht:IFRS9Member
852 Components of equity [axis] Axis ifrs-full:ComponentsOfEquityAxis
853 Equity [member] Member ifrs-full:EquityMember
854 Total retained earnings [Member] Member ifrs-full:RetainedEarningsMember
855 Noncontrolling interests [Member] Member ifrs-full:NoncontrollingInterestsMember
856 Disclosure Of Initial Application Of Standards Or Interpretations [Line Items] LineItems ifrs-full:DisclosureOfInitialApplicationOfStandardsOrInterpretationsLineItems
857 Financial Assets, Measurement Category, IAS 39 Concept (Text/String) For Period ifrs-full:FinancialAssetsMeasurementCategoryImmediatelyBeforeInitialApplicationOfIFRS9
858 Financial Assets, Measurement Category, IFRS 9 Concept (Text/String) For Period ifrs-full:FinancialAssetsMeasurementCategoryImmediatelyAfterInitialApplicationOfIFRS9
859 Financial Assets, Carrying Amount, IAS 39 Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsCarryingAmountImmediatelyBeforeInitialApplicationOfIFRS9
860 Financial Assets, Carrying Amount, IFRS 9 Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsCarryingAmountImmediatelyAfterInitialApplicationOfIFRS9
861 Financial Liabilities, Measurement Category, IAS 39 Concept (Text/String) For Period ifrs-full:FinancialLiabilitiesMeasurementCategoryImmediatelyBeforeInitialApplicationOfIFRS9
862 Financial Liabilities, Measurement Category, IFRS 9 Concept (Text/String) For Period ifrs-full:FinancialLiabilitiesMeasurementCategoryImmediatelyAfterInitialApplicationOfIFRS9
863 Financial Liabilities, Carrying Amount, IAS 39 Concept (Monetary) As Of Credit ifrs-full:FinancialLiabilitiesCarryingAmountImmediatelyBeforeInitialApplicationOfIFRS9
864 Financial Liabilities, Carrying Amount, IFRS 9 Concept (Monetary) As Of Credit ifrs-full:FinancialLiabilitiesCarryingAmountImmediatelyAfterInitialApplicationOfIFRS9
865 Financial assets measured at FVTPL Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAtFairValueThroughProfitOrLossMandatorilyMeasuredAtFairValue
866 Add: reclassification from available for sale (IAS 39) - mandatory reclassification Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAvailableforsale
867 Financial assets at fair value through profit or loss - subtotal Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAtFairValueThroughProfitOrLoss
868 Financial liabilities measured at FVTPL Concept (Monetary) As Of Credit ifrs-full:FinancialLiabilitiesAtFairValueThroughProfitOrLoss
869 Financial assets measured at FVOCI- equity investments Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsMeasuredAtFairValueThroughOtherComprehensiveIncome
870 Add: reclassification from available for sale (IAS 39) - designated at January 1, 2018 Concept (Monetary) As Of Debit ifrs-full:FairValueOfInvestmentsInEquityInstrumentsDesignatedAsMeasuredAtFairValueThroughOtherComprehensiveIncome
871 Financial assets at fair value through other comprehensive income - equity investments - subtotal Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAtFairValueThroughOtherComprehensiveIncome
872 Financial assets measured at Amortized cost Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAtAmortisedCost
873 Add: reclassification from loans and receivables (IAS 39) Concept (Monetary) As Of Debit ifrs-full:LoansAndReceivables
874 Financial Assets measured at amortized cost - subtotal Concept (Monetary) As Of Debit ifrs-full:FinancialAssets
875 Financial liabilities measured at amortized cost Concept (Monetary) As Of Credit ifrs-full:FinancialLiabilitiesAtAmortisedCost
876 Add: reclassification from amortized cost (IAS 39) Concept (Monetary) As Of Credit ifrs-full:CurrentFinancialLiabilitiesAtAmortisedCost
877 Financial Liabilities measured at amortized cost - subtotal Concept (Monetary) As Of Credit ifrs-full:CurrentFinancialLiabilities
878 Hedging financial liabilities Concept (Monetary) As Of Credit ifrs-full:DerivativeFinancialLiabilitiesHeldForHedging
879 Add: reclassification from Hedging derivative instrument (IAS 39) Concept (Monetary) As Of Credit ifrs-full:HedgingInstrumentLiabilities
880 Hedging financial liabilities - subtotal Concept (Monetary) As Of Credit ifrs-full:DerivativeFinancialLiabilities
881 Total Concept (Monetary) As Of Debit ifrs-full:NetAssetsLiabilities
882 100910 - Disclosure - Application of New and Amended International Financial Reporting Standards - Additional Information (Detail) Network

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883 Disclosure Of Initial Application Of Standards Or Interpretations [Table] Table

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 ifrs-full:DisclosureOfInitialApplicationOfStandardsOrInterpretationsTable
884 Classes of assets [axis] Axis ifrs-full:ClassesOfAssetsAxis
885 Assets [member] Member ifrs-full:ClassesOfAssetsMember
886 Other Equity [Member] Member ifrs-full:OtherEquitySecuritiesMember
887 Components of equity [axis] Axis ifrs-full:ComponentsOfEquityAxis
888 Equity [member] Member ifrs-full:EquityMember
889 Total retained earnings [Member] Member ifrs-full:RetainedEarningsMember
890 Retrospective application and retrospective restatement [axis] Axis ifrs-full:RetrospectiveApplicationAndRetrospectiveRestatementAxis
891 Currently stated [member] Member ifrs-full:RestatedMember
892 Remeasured FVOCI [Member] Member cht:RemeasuredFVOCIMember
893 Reclassification of Impairment [Member] Member cht:ReclassificationOfImpairmentMember
894 Increase (Decrease) Due to Application of IFRS 9 [Member] Member cht:IncreaseDecreaseDueToApplicationOfIFRS9Member
895 Non-adjusting events after reporting period [axis] Axis ifrs-full:NonadjustingEventsAfterReportingPeriodAxis
896 Non-adjusting events after reporting period [member] Member ifrs-full:NonadjustingEventsMember
897 Classification of assets as held for sale [member] Member ifrs-full:ClassificationOfAssetsAsHeldForSaleMember
898 Disclosure Of Initial Application Of Standards Or Interpretations [Line Items] LineItems ifrs-full:DisclosureOfInitialApplicationOfStandardsOrInterpretationsLineItems
899 Unrealized gain or loss on available-for-sale financial assets Concept (Monetary) As Of Credit cht:UnrealizedGainOrLossOnAvailableForSaleFinancialAssets
900 Total effect on assets Concept (Monetary) As Of Debit cht:NetEffectOnAssets
901 Total effect on equity Concept (Monetary) As Of Credit cht:NetEffectOnEquity
902 NONCONTROLLING INTERESTS Concept (Monetary) As Of Credit ifrs-full:NoncontrollingInterests
903 Unappropriated earnings Concept (Monetary) As Of Credit cht:UnappropriatedRetainedEarnings
904 Tax obligation Concept (Monetary) For Period Debit ifrs-full:CurrentTaxExpenseIncome
905 Deferred income tax liabilities Concept (Monetary) As Of Credit ifrs-full:DeferredTaxLiabilities
906 100920 - Disclosure - Application of New and Amended International Financial Reporting Standards - Schedule of Anticipated Impacts on Assets, Liabilities and Equity from Applying IFRS 15 Retrospectivly and On the Balance Sheet Date (Detail) Network

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907 Disclosure Of Initial Application Of Standards Or Interpretations [Table] Table

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 ifrs-full:DisclosureOfInitialApplicationOfStandardsOrInterpretationsTable
908 Initially applied IFRSs [axis] Axis ifrs-full:InitiallyAppliedIFRSsAxis
909 Initially applied IFRSs [member] Member ifrs-full:InitiallyAppliedIFRSsMember
910 IFRS 15 [Member] Member cht:IFRS15Member
911 Retrospective application and retrospective restatement [axis] Axis ifrs-full:RetrospectiveApplicationAndRetrospectiveRestatementAxis
912 Currently stated [member] Member ifrs-full:RestatedMember
913 Carrying Amount Before Retrospective Adjustments [Member] Member cht:CarryingAmountBeforeRetrospectiveAdjustmentsMember
914 Increase (Decrease) Due to Application of IFRS 15 [Member] Member ifrs-full:IncreaseDecreaseDueToApplicationOfIFRS15Member
915 Carrying Amount After Retrospective Adjustments [Member] Member cht:CarryingAmountAfterRetrospectiveAdjustmentsMember
916 Disclosure Of Initial Application Of Standards Or Interpretations [Line Items] LineItems ifrs-full:DisclosureOfInitialApplicationOfStandardsOrInterpretationsLineItems
917 Contract assets - current Concept (Monetary) As Of Debit ifrs-full:CurrentContractAssets
918 Trade notes and accounts receivable, net Concept (Monetary) As Of Debit ifrs-full:CurrentTradeReceivables
919 Inventories Concept (Monetary) As Of Debit ifrs-full:Inventories
920 Prepayments - current Concept (Monetary) As Of Debit ifrs-full:CurrentPrepayments
921 Other current assets Concept (Monetary) As Of Debit ifrs-full:OtherCurrentAssets
922 Contract assets - noncurrent Concept (Monetary) As Of Debit ifrs-full:NoncurrentContractAssets
923 Incremental costs of obtaining contracts Concept (Monetary) As Of Debit ifrs-full:AssetsRecognisedFromCostsToObtainOrFulfilContractsWithCustomers
924 Total effect on assets Concept (Monetary) As Of Debit cht:NetEffectOnAssets
925 Contract liabilities - current Concept (Monetary) As Of Credit ifrs-full:CurrentContractLiabilities
926 Current tax liabilities Concept (Monetary) As Of Credit ifrs-full:CurrentTaxLiabilitiesCurrent
927 Provisions Concept (Monetary) As Of Credit ifrs-full:CurrentProvisions
928 Advance receipts Concept (Monetary) As Of Credit ifrs-full:CurrentAdvances
929 Other current liabilities Concept (Monetary) As Of Credit ifrs-full:OtherCurrentLiabilities
930 Contract liabilities - noncurrent Concept (Monetary) As Of Credit ifrs-full:NoncurrentContractLiabilities
931 Deferred revenue Concept (Monetary) As Of Credit ifrs-full:DeferredIncomeClassifiedAsNoncurrent
932 Other noncurrent liabilities Concept (Monetary) As Of Credit ifrs-full:OtherNoncurrentLiabilities
933 Total effect on liabilities Concept (Monetary) As Of Credit cht:NetEffectOnLiabilities
934 Total effect on equity (unappropriated earnings) Concept (Monetary) As Of Credit cht:EffectOnEquityUnappropriatedEarnings
935 100930 - Disclosure - Application of New and Amended International Financial Reporting Standards - Schedule of Increase (Decrease) in Net Income Resulting from the Application of IFRS 15 (Detail) Network

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936 Disclosure Of Initial Application Of Standards Or Interpretations [Table] Table

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937 Initially applied IFRSs [axis] Axis ifrs-full:InitiallyAppliedIFRSsAxis
938 Initially applied IFRSs [member] Member ifrs-full:InitiallyAppliedIFRSsMember
939 IFRS 15 [Member] Member cht:IFRS15Member
940 Retrospective application and retrospective restatement [axis] Axis ifrs-full:RetrospectiveApplicationAndRetrospectiveRestatementAxis
941 Currently stated [member] Member ifrs-full:RestatedMember
942 Increase (Decrease) Due to Application of IFRS 15 [Member] Member ifrs-full:IncreaseDecreaseDueToApplicationOfIFRS15Member
943 Disclosure Of Initial Application Of Standards Or Interpretations [Line Items] LineItems ifrs-full:DisclosureOfInitialApplicationOfStandardsOrInterpretationsLineItems
944 Revenues Concept (Monetary) For Period Credit ifrs-full:Revenue
945 Operating costs Concept (Monetary) For Period Debit ifrs-full:CostOfSales
946 Operating expenses Concept (Monetary) For Period Debit ifrs-full:OperatingExpenseExcludingCostOfSales
947 Income from operations Concept (Monetary) For Period Credit ifrs-full:ProfitLossFromOperatingActivities
948 INCOME TAX EXPENSE Concept (Monetary) For Period Debit ifrs-full:IncomeTaxExpenseContinuingOperations
949 Net income Concept (Monetary) For Period Credit ifrs-full:ProfitLoss
950 Decrease in net income attributable to: Abstract ifrs-full:ProfitLossAttributableToAbstract
951 Stockholders of the parent Concept (Monetary) For Period Credit ifrs-full:ProfitLossAttributableToOwnersOfParent
952 Noncontrolling interests Concept (Monetary) For Period Credit ifrs-full:ProfitLossAttributableToNoncontrollingInterests
953 NET INCOME Concept (Monetary) For Period Credit ifrs-full:ProfitLoss
954 EARNINGS PER SHARE Abstract ifrs-full:EarningsPerShareAbstract
955 Basic Concept (Share) For Period ifrs-full:BasicEarningsLossPerShare
956 Diluted Concept (Share) For Period ifrs-full:DilutedEarningsLossPerShare
957 100940 - Disclosure - Application of New and Amended International Financial Reporting Standards - Schedule of Anticipated Impacts on Assets, Liabilities and Equity from Retrospective Application of IFRS 16 (Detail) Network

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958 Disclosure Of Initial Application Of Standards Or Interpretations [Table] Table

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 ifrs-full:DisclosureOfInitialApplicationOfStandardsOrInterpretationsTable
959 Initially applied IFRSs [axis] Axis ifrs-full:InitiallyAppliedIFRSsAxis
960 Initially applied IFRSs [member] Member ifrs-full:InitiallyAppliedIFRSsMember
961 IFRS 16 [Member] Member cht:IFRS16Member
962 Retrospective application and retrospective restatement [axis] Axis ifrs-full:RetrospectiveApplicationAndRetrospectiveRestatementAxis
963 Currently stated [member] Member ifrs-full:RestatedMember
964 Increase (Decrease) Due to Changes Required by IFRSs [Member] Member ifrs-full:IncreaseDecreaseDueToChangesInAccountingPolicyRequiredByIFRSsMember
965 Disclosure Of Initial Application Of Standards Or Interpretations [Line Items] LineItems ifrs-full:DisclosureOfInitialApplicationOfStandardsOrInterpretationsLineItems
966 Prepayments - current Concept (Monetary) As Of Debit ifrs-full:CurrentPrepayments
967 Property, plant and equipment Concept (Monetary) As Of Debit ifrs-full:PropertyPlantAndEquipment
968 Right-of-use assets Concept (Monetary) As Of Debit ifrs-full:RightofuseAssets
969 Deferred income tax assets Concept (Monetary) As Of Debit ifrs-full:DeferredTaxAssets
970 Prepayments - noncurrent Concept (Monetary) As Of Debit ifrs-full:NoncurrentPrepayments
971 Total effect on assets Concept (Monetary) As Of Debit cht:NetEffectOnAssets
972 Contract liabilities - current Concept (Monetary) As Of Credit ifrs-full:CurrentContractLiabilities
973 Lease liabilities - current Concept (Monetary) As Of Credit ifrs-full:CurrentLeaseLiabilities
974 Other payables Concept (Monetary) As Of Credit ifrs-full:OtherCurrentPayables
975 Other current liabilities Concept (Monetary) As Of Credit ifrs-full:OtherCurrentLiabilities
976 Contract liabilities - noncurrent Concept (Monetary) As Of Credit ifrs-full:NoncurrentContractLiabilities
977 Deferred income tax liabilities Concept (Monetary) As Of Credit ifrs-full:DeferredTaxLiabilities
978 Lease liabilities - noncurrent Concept (Monetary) As Of Credit ifrs-full:NoncurrentLeaseLiabilities
979 Other noncurrent liabilities Concept (Monetary) As Of Credit ifrs-full:OtherNoncurrentLiabilities
980 Total effect on liabilities Concept (Monetary) As Of Credit cht:NetEffectOnLiabilitiesDeferredIncomeTaxLiabilities
981 Unappropriated earnings Concept (Monetary) As Of Credit cht:UnappropriatedRetainedEarnings
982 NONCONTROLLING INTERESTS Concept (Monetary) As Of Credit ifrs-full:NoncontrollingInterests
983 Total effect on equity Concept (Monetary) As Of Credit cht:NetEffectOnEquity
984 100950 - Disclosure - U.S. Dollar Amounts - Additional Information (Detail) Network

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*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureUSDollarAmountsAdditionalInformationDetail
985 Implied Table Table

*

*

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986 Foreign Exchange Rates [Abstract] Abstract ifrs-full:ForeignExchangeRatesAbstract
987 Exchange rate used for convenience translations Concept (Decimal) As Of ifrs-full:ClosingForeignExchangeRate
988 100960 - Disclosure - Cash and Cash Equivalents - Summary of Cash and Cash Equivalents (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureCashAndCashEquivalentsSummaryOfCashAndCashEquivalentsDetail
989 Implied Table Table

*

*

 implied:Table
990 Cash And Cash Equivalents [Abstract] Abstract ifrs-full:CashAndCashEquivalentsAbstract
991 Cash Abstract ifrs-full:CashAbstract
992 Cash on hand Concept (Monetary) As Of Debit ifrs-full:CashOnHand
993 Bank deposits Concept (Monetary) As Of Debit ifrs-full:BalancesWithBanks
994 Cash Concept (Monetary) As Of Debit ifrs-full:Cash
995 Cash equivalents (investments with maturities of less than three months) Abstract ifrs-full:CashEquivalentsAbstract
996 Commercial paper Concept (Monetary) As Of Debit ifrs-full:ShorttermInvestmentsClassifiedAsCashEquivalents
997 Negotiable certificate of deposit Concept (Monetary) As Of Debit cht:NegotiableCertificatesOfDepositAmount
998 Time deposits Concept (Monetary) As Of Debit cht:TimeDepositsWithBanks
999 Cash equivalents Concept (Monetary) As Of Debit ifrs-full:CashEquivalents
1000 Cash and cash equivalents Concept (Monetary) As Of Debit ifrs-full:CashAndCashEquivalents
1001 100970 - Disclosure - Cash and Cash Equivalents - Annual Yield Rates of Bank Deposits, Commercial Paper, Negotiable Certificates of Deposit and Time Deposits (Detail) Network

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 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureCashAndCashEquivalentsAnnualYieldRatesOfBankDepositsCommercialPaperNegotiableCertificatesOfDepositAndTimeDepositsDetail
1002 Cash And Cash Equivalents [Table] Table

*

*

 cht:CashAndCashEquivalentsTable
1003 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
1004 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
1005 Bank deposits [Member] Member cht:BankDepositsMember
1006 Commercial paper [Member] Member cht:CommercialPaper1Member
1007 Negotiable certificate of deposit [Member] Member cht:NegotiableCertificateOfDepositMember
1008 Time deposits [Member] Member cht:TimeDepositsMember
1009 Range [axis] Axis ifrs-full:RangeAxis
1010 Ranges [member] Member ifrs-full:RangesMember
1011 Bottom of range [Member] Member ifrs-full:BottomOfRangeMember
1012 Top of Range [Member] Member ifrs-full:TopOfRangeMember
1013 Disclosure of cash and cash equivalents [Line Items] LineItems cht:DisclosureOfCashAndCashEquivalentsLineItems
1014 Yield rate Concept (Percent) As Of cht:YieldRate
1015 100980 - Disclosure - Financial Instruments at Fair Value Through Profit or Loss - Summary of Financial Instruments at Fair Value through Profit or Loss (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureFinancialInstrumentsAtFairValueThroughProfitOrLossSummaryOfFinancialInstrumentsAtFairValueThroughProfitOrLossDetail
1016 Disclosure Of Financial Instruments [Table] Table

*

*

 ifrs-full:DisclosureOfFinancialInstrumentsTable
1017 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
1018 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
1019 Non listed stocks domestic [Member] Member cht:NonListedStocksDomesticMember
1020 Non listed stocks foreign [Member] Member cht:NonListedStocksForeignMember
1021 Disclosure of detailed information about financial instruments [Line Items] LineItems ifrs-full:DisclosureOfFinancialInstrumentsLineItems
1022 Financial assets-noncurrent Abstract ifrs-full:CategoriesOfNoncurrentFinancialAssetsAbstract
1023 Non-derivatives Concept (Monetary) As Of Debit ifrs-full:NoncurrentDerivativeFinancialAssets
1024 Financial assets held for trading, Derivatives (not designated for hedge), Forward exchange contracts Concept (Monetary) As Of Debit ifrs-full:CurrentFinancialAssetsAtFairValueThroughProfitOrLossClassifiedAsHeldForTrading
1025 Financial liabilities-current Abstract ifrs-full:CategoriesOfNoncurrentFinancialLiabilitiesAbstract
1026 Financial liabilities held for trading, Derivatives (not designated for hedge), Forward exchange contracts Concept (Monetary) As Of Credit ifrs-full:CurrentFinancialLiabilitiesAtFairValueThroughProfitOrLossClassifiedAsHeldForTrading
1027 100990 - Disclosure - Financial Instruments at Fair Value Through Profit or Loss - Outstanding Forward Exchange Contracts Not Designated for Hedge (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureFinancialInstrumentsAtFairValueThroughProfitOrLossOutstandingForwardExchangeContractsNotDesignatedForHedgeDetail
1028 Disclosure Of Financial Instruments [Table] Table

*

*

 ifrs-full:DisclosureOfFinancialInstrumentsTable
1029 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
1030 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
1031 Forward exchange contracts [Member] Member ifrs-full:ForwardContractMember
1032 Currency Axis srt:CurrencyAxis
1033 All Currencies Member currency:AllCurrenciesDomain
1034 EUR [Member] Member currency:EUR
1035 USD [Member] Member currency:USD
1036 Disclosure of detailed information about financial instruments [Line Items] LineItems ifrs-full:DisclosureOfFinancialInstrumentsLineItems
1037 Currency Concept (Text/String) For Period cht:DerivativeContractCrossCurrency
1038 Maturity Period Concept (Text/String) For Period cht:DescriptionOfDerivativeFinancialInstrumentsMaturityPeriod
1039 Contract Amount Concept (Monetary) As Of invest:DerivativeNotionalAmount
1040 101000 - Disclosure - Financial Assets at Fair Value through Other Comprehensive Income Noncurrent - Summary of Financial Assets at Fair Value through Other Comprehensive Income Noncurrent (Detail) Network

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*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureFinancialAssetsAtFairValueThroughOtherComprehensiveIncomeNoncurrentSummaryOfFinancialAssetsAtFairValueThroughOtherComprehensiveIncomeNoncurrentDetail
1041 Noncurrent Financial Assets At Fair Value Through Other Comprehensive Income [Table] Table

*

*

 cht:NoncurrentFinancialAssetsAtFairValueThroughOtherComprehensiveIncomeTable
1042 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
1043 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
1044 Domestic listed stocks [Member] Member cht:DomesticListedStocksMember
1045 Domestic non-listed stocks [Member] Member cht:DomesticNonlistedStocksMember
1046 Foreign non-listed stocks [Member] Member cht:ForeignNonlistedStocksMember
1047 Disclosure of financial assets [Line Items] LineItems cht:NoncurrentFinancialAssetsAtFairValueThroughOtherComprehensiveIncomeLineItems
1048 Financial assets at fair value through other comprehensive income Concept (Monetary) As Of Debit ifrs-full:NoncurrentFinancialAssetsAtFairValueThroughOtherComprehensiveIncome
1049 101010 - Disclosure - Financial Assets at Fair Value through Other Comprehensive Income Noncurrent - Additional Information (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureFinancialAssetsAtFairValueThroughOtherComprehensiveIncomeNoncurrentAdditionalInformationDetail
1050 Implied Table Table

*

*

 implied:Table
1051 Noncurrent Financial Assets At Fair Value Through Other Comprehensive Income [Abstract] Abstract ifrs-full:NoncurrentFinancialAssetsAtFairValueThroughOtherComprehensiveIncomeAbstract
1052 Dividends received Concept (Monetary) For Period Debit ifrs-full:DividendsReceived
1053 101020 - Disclosure - Available-for-sale Financial Assets Non Current - Summary of Available-for-sale Financial Assets Non Current (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureAvailableForSaleFinancialAssetsNonCurrentSummaryOfAvailableForSaleFinancialAssetsNonCurrentDetail
1054 Disclosure Of Financial Assets [Table] Table

*

*

 ifrs-full:DisclosureOfFinancialAssetsTable
1055 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
1056 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
1057 Domestic listed stocks [Member] Member cht:DomesticListedStocksMember
1058 Domestic non-listed stocks [Member] Member cht:DomesticNonlistedStocksMember
1059 Foreign non-listed stocks [Member] Member cht:ForeignNonlistedStocksMember
1060 Disclosure Of Financial Assets [Line Items] LineItems ifrs-full:DisclosureOfFinancialAssetsLineItems
1061 Available-for-sale financial assets, non current Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAvailableforsale
1062 101030 - Disclosure - Available-for-sale Financial Assets Non Current - Additional Information (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureAvailableForSaleFinancialAssetsNonCurrentAdditionalInformationDetail
1063 Disclosure Of Financial Assets [Table] Table

*

*

 ifrs-full:DisclosureOfFinancialAssetsTable
1064 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
1065 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
1066 Domestic listed stocks [Member] Member cht:DomesticListedStocksMember
1067 Non-listed stocks [Member] Member cht:NonlistedStocksMember
1068 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
1069 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
1070 Taiwania Capital Buffalo Fund Co Ltd [Member] Member cht:TaiwaniaCapitalBuffaloFundCoLtdMember
1071 Disclosure Of Financial Assets [Line Items] LineItems ifrs-full:DisclosureOfFinancialAssetsLineItems
1072 Impairment loss on available-for-sale financial assets Concept (Monetary) For Period Debit cht:ImpairmentLossReversalOfImpairmentLossRecognisedInProfitOrLossAvailableforsaleFinancialAssets
1073 Amount invested in investment entity Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAvailableforsale
1074 Ownership percentage in investment entity Concept (Percent) For Period cht:EquityOwnershipPercentageInInvestmentEntity
1075 Carrying value of non-listed available-for-sale financial assets disposed Concept (Monetary) For Period Debit cht:CarryingValueOfAvailableforsaleFinancialAssetsDisposed
1076 Gains (losses) from disposal of available-for-sale assets Concept (Monetary) For Period Credit ifrs-full:GainsLossesOnAvailableforsaleFinancialAssets
1077 101040 - Disclosure - Trade Notes and Accounts Receivable, Net - Summary of Trade Notes and Accounts Receivable, Net (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureTradeNotesAndAccountsReceivableNetSummaryOfTradeNotesAndAccountsReceivableNetDetail
1078 Disclosure Of Financial Assets [Table] Table

*

*

 ifrs-full:DisclosureOfFinancialAssetsTable
1079 Carrying amount, accumulated depreciation, amortisation and impairment and gross carrying amount [axis] Axis ifrs-full:CarryingAmountAccumulatedDepreciationAmortisationAndImpairmentAndGrossCarryingAmountAxis
1080 Carrying amount [member] Member ifrs-full:CarryingAmountMember
1081 Gross carrying amount [Member] Member ifrs-full:GrossCarryingAmountMember
1082 Disclosure Of Financial Assets [Line Items] LineItems ifrs-full:DisclosureOfFinancialAssetsLineItems
1083 Trade notes and accounts receivable Concept (Monetary) As Of Debit ifrs-full:CurrentTradeReceivables
1084 Less: Loss allowance Concept (Monetary) As Of Credit ifrs-full:AllowanceAccountForCreditLossesOfFinancialAssets
1085 101050 - Disclosure - Trade Notes and Accounts Receivable, Net - Additional Information (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureTradeNotesAndAccountsReceivableNetAdditionalInformationDetail
1086 Disclosure Of Financial Assets [Table] Table

*

*

 ifrs-full:DisclosureOfFinancialAssetsTable
1087 Range [axis] Axis ifrs-full:RangeAxis
1088 Ranges [member] Member ifrs-full:RangesMember
1089 Bottom of Range [Member] Member ifrs-full:BottomOfRangeMember
1090 Top of Range [Member] Member ifrs-full:TopOfRangeMember
1091 Disclosure Of Financial Assets [Line Items] LineItems ifrs-full:DisclosureOfFinancialAssetsLineItems
1092 Average credit terms Concept (xbrli:durationItemType) For Period cht:AverageCreditTerms
1093 Threshold period when notes and accounts receivable due are unlikely to be collected and therefore the allowance of notes and accounts receivable are recognized Concept (xbrli:durationItemType) For Period cht:RecoveryPeriodAllowedForNotesAndAccountsReceivable
1094 Percentage of allowance of notes and accounts receivable overdue recognized Concept (Percent) For Period cht:PercentageOfAllowanceOfNotesAndAccountsReceivableOverdueRecognized
1095 101060 - Disclosure - Trade Notes and Accounts Receivable, Net - Aging Analysis for Trade Notes and Accounts Receivable (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureTradeNotesAndAccountsReceivableNetAgingAnalysisForTradeNotesAndAccountsReceivableDetail
1096 Disclosure Of Financial Assets That Are Either Past Due Or Impaired [Table] Table

*

*

 ifrs-full:DisclosureOfFinancialAssetsThatAreEitherPastDueOrImpairedTable
1097 Carrying amount, accumulated depreciation, amortisation and impairment and gross carrying amount [axis] Axis ifrs-full:CarryingAmountAccumulatedDepreciationAmortisationAndImpairmentAndGrossCarryingAmountAxis
1098 Carrying amount [member] Member ifrs-full:CarryingAmountMember
1099 Gross carrying amount [Member] Member ifrs-full:GrossCarryingAmountMember
1100 Past due status [axis] Axis ifrs-full:PastDueStatusAxis
1101 Past due status [member] Member ifrs-full:PastDueStatusMember
1102 Non-overdue [Member] Member ifrs-full:CurrentMember
1103 Less than 30 days [Member] Member ifrs-full:NotLaterThanOneMonthMember
1104 31-60 days [Member] Member ifrs-full:LaterThanOneMonthAndNotLaterThanTwoMonthsMember
1105 61-90 days [Member] Member ifrs-full:LaterThanTwoMonthsAndNotLaterThanThreeMonthsMember
1106 91-120 days [Member] Member ifrs-full:LaterThanThreeMonthsAndNotLaterThanFourMonthsMember
1107 121-180 days [Member] Member cht:LaterThanFourMonthsAndNotLaterThanSixMonthsMember
1108 More than 181 days [Member] Member ifrs-full:LaterThanSixMonthsMember
1109 Disclosure of financial assets that are either past due or impaired [Line Items] LineItems ifrs-full:DisclosureOfFinancialAssetsThatAreEitherPastDueOrImpairedLineItems
1110 Trade notes and accounts receivable Concept (Monetary) As Of Debit ifrs-full:CurrentTradeReceivables
1111 101070 - Disclosure - Trade Notes and Accounts Receivable, Net - Receivables Past Due but Not Impaired (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureTradeNotesAndAccountsReceivableNetReceivablesPastDueButNotImpairedDetail
1112 Disclosure Of Financial Assets That Are Either Past Due Or Impaired [Table] Table

*

*

 ifrs-full:DisclosureOfFinancialAssetsThatAreEitherPastDueOrImpairedTable
1113 Impairment of financial assets [axis] Axis ifrs-full:ImpairmentOfFinancialAssetsAxis
1114 Entity's total for impairment of financial assets [member] Member ifrs-full:EntitysTotalForImpairmentOfFinancialAssetsMember
1115 Receivables past due but not impaired [Member] Member ifrs-full:FinancialAssetsPastDueButNotImpairedMember
1116 Past due status [axis] Axis ifrs-full:PastDueStatusAxis
1117 Past due status [member] Member ifrs-full:PastDueStatusMember
1118 Less than 30 days [Member] Member ifrs-full:NotLaterThanOneMonthMember
1119 31-60 days [Member] Member ifrs-full:LaterThanOneMonthAndNotLaterThanTwoMonthsMember
1120 61-90 days [Member] Member ifrs-full:LaterThanTwoMonthsAndNotLaterThanThreeMonthsMember
1121 91-120 days [Member] Member ifrs-full:LaterThanThreeMonthsAndNotLaterThanFourMonthsMember
1122 121-180 days [Member] Member cht:LaterThanFourMonthsAndNotLaterThanSixMonthsMember
1123 More than 181 days [Member] Member ifrs-full:LaterThanSixMonthsMember
1124 Disclosure of financial assets that are either past due or impaired [Line Items] LineItems ifrs-full:DisclosureOfFinancialAssetsThatAreEitherPastDueOrImpairedLineItems
1125 Trade notes and accounts receivable Concept (Monetary) As Of Debit ifrs-full:CurrentTradeReceivables
1126 101080 - Disclosure - Trade Notes and Accounts Receivable, Net - Movements of Allowance for Doubtful Accounts (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureTradeNotesAndAccountsReceivableNetMovementsOfAllowanceForDoubtfulAccountsDetail
1127 Disclosure Of Financial Assets [Table] Table

*

*

 ifrs-full:DisclosureOfFinancialAssetsTable
1128 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
1129 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
1130 Trade notes and accounts receivable [Member] Member ifrs-full:TradeReceivablesMember
1131 Method of assessment of expected credit losses [axis] Axis ifrs-full:MethodOfAssessmentOfExpectedCreditLossesAxis
1132 Method of assessment of expected credit losses [member] Member ifrs-full:MethodOfAssessmentOfExpectedCreditLossesMember
1133 Individually assessed for impairment [Member] Member ifrs-full:ExpectedCreditLossesIndividuallyAssessedMember
1134 Collectively assessed for impairment [Member] Member ifrs-full:ExpectedCreditLossesCollectivelyAssessedMember
1135 Disclosure Of Financial Assets [Line Items] LineItems ifrs-full:DisclosureOfFinancialAssetsLineItems
1136 Beginning balance Concept (Monetary) As Of Credit ifrs-full:AllowanceAccountForCreditLossesOfFinancialAssets
1137 Add: Provision for credit loss or doubtful accounts Concept (Monetary) For Period Debit ifrs-full:ImpairmentLossReversalOfImpairmentLossRecognisedInProfitOrLossTradeReceivables
1138 Less: Amounts written off Concept (Monetary) For Period Debit ifrs-full:UtilisationAllowanceAccountForCreditLossesOfFinancialAssets
1139 Ending balance Concept (Monetary) As Of Credit ifrs-full:AllowanceAccountForCreditLossesOfFinancialAssets
1140 101090 - Disclosure - Trade Notes and Accounts Receivable, Net - Provision Matrix Arising from Telecommunications and Project Business (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureTradeNotesAndAccountsReceivableNetProvisionMatrixArisingFromTelecommunicationsAndProjectBusinessDetail
1141 Disclosure Of Financial Assets That Are Either Past Due Or Impaired [Table] Table

*

*

 ifrs-full:DisclosureOfFinancialAssetsThatAreEitherPastDueOrImpairedTable
1142 Past due status [axis] Axis ifrs-full:PastDueStatusAxis
1143 Past due status [member] Member ifrs-full:PastDueStatusMember
1144 Not Past Due [Member] Member ifrs-full:CurrentMember
1145 Less than 30 days [Member] Member ifrs-full:NotLaterThanOneMonthMember
1146 31-60 days [Member] Member ifrs-full:LaterThanOneMonthAndNotLaterThanTwoMonthsMember
1147 61-90 days [Member] Member ifrs-full:LaterThanTwoMonthsAndNotLaterThanThreeMonthsMember
1148 91-120 days [Member] Member ifrs-full:LaterThanThreeMonthsAndNotLaterThanFourMonthsMember
1149 121-180 days [Member] Member cht:LaterThanFourMonthsAndNotLaterThanSixMonthsMember
1150 Over 181 Days [Member] Member ifrs-full:LaterThanSixMonthsMember
1151 Business combinations [axis] Axis ifrs-full:BusinessCombinationsAxis
1152 Entity's total for business combinations [member] Member ifrs-full:EntitysTotalForBusinessCombinationsMember
1153 Telecommunications Business [Member] Member cht:TelecommunicationsBusinessMember
1154 Project Business [Member] Member cht:ProjectBusinessMember
1155 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
1156 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
1157 Amortized Cost [Member] Member ifrs-full:FinancialAssetsAtAmortisedCostMember
1158 Carrying amount, accumulated depreciation, amortisation and impairment and gross carrying amount [axis] Axis ifrs-full:CarryingAmountAccumulatedDepreciationAmortisationAndImpairmentAndGrossCarryingAmountAxis
1159 Carrying amount [member] Member ifrs-full:CarryingAmountMember
1160 Gross Carrying Amount [Member] Member ifrs-full:GrossCarryingAmountMember
1161 Type of measurement of expected credit losses [axis] Axis ifrs-full:TypeOfMeasurementOfExpectedCreditLossesAxis
1162 Type of measurement of expected credit losses [member] Member ifrs-full:TypeOfMeasurementOfExpectedCreditLossesMember
1163 Loss allowance [Member] Member ifrs-full:LifetimeExpectedCreditLossesMember
1164 Range [axis] Axis ifrs-full:RangeAxis
1165 Ranges [member] Member ifrs-full:RangesMember
1166 Bottom of Range [Member] Member ifrs-full:BottomOfRangeMember
1167 Top of Range [Member] Member ifrs-full:TopOfRangeMember
1168 Disclosure of financial assets that are either past due or impaired [Line Items] LineItems ifrs-full:DisclosureOfFinancialAssetsThatAreEitherPastDueOrImpairedLineItems
1169 Trade notes and accounts receivable Concept (Monetary) As Of Debit ifrs-full:CurrentTradeReceivables
1170 Less: Loss allowance Concept (Monetary) As Of Credit ifrs-full:AllowanceAccountForCreditLossesOfFinancialAssets
1171 Expected credit loss rate Concept (Percent) As Of ifrs-full:ExpectedCreditLossRate
1172 101100 - Disclosure - Trade Notes and Accounts Receivable, Net - Provision Matrix Arising from Telecommunications and Project Business (Parenthetical) (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureTradeNotesAndAccountsReceivableNetProvisionMatrixArisingFromTelecommunicationsAndProjectBusinessParentheticalDetail
1173 Disclosure Of Financial Assets That Are Either Past Due Or Impaired [Table] Table

*

*

 ifrs-full:DisclosureOfFinancialAssetsThatAreEitherPastDueOrImpairedTable
1174 Business combinations [axis] Axis ifrs-full:BusinessCombinationsAxis
1175 Entity's total for business combinations [member] Member ifrs-full:EntitysTotalForBusinessCombinationsMember
1176 Project Business [Member] Member cht:ProjectBusinessMember
1177 Range [axis] Axis ifrs-full:RangeAxis
1178 Ranges [member] Member ifrs-full:RangesMember
1179 Bottom of Range [Member] Member ifrs-full:BottomOfRangeMember
1180 Top of Range [Member] Member ifrs-full:TopOfRangeMember
1181 Disclosure of financial assets that are either past due or impaired [Line Items] LineItems ifrs-full:DisclosureOfFinancialAssetsThatAreEitherPastDueOrImpairedLineItems
1182 Expected credit loss rate Concept (Percent) As Of ifrs-full:ExpectedCreditLossRate
1183 101110 - Disclosure - Inventories - Summary of Inventories (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureInventoriesSummaryOfInventoriesDetail
1184 Implied Table Table

*

*

 implied:Table
1185 Classes Of Inventories [Abstract] Abstract ifrs-full:ClassesOfInventoriesAbstract
1186 Merchandise Concept (Monetary) As Of Debit ifrs-full:Merchandise
1187 Project in process Concept (Monetary) As Of Debit cht:CurrentProjectInProgress
1188 Work in process Concept (Monetary) As Of Debit ifrs-full:WorkInProgress
1189 Raw materials Concept (Monetary) As Of Debit ifrs-full:RawMaterials
1190 Inventories subtotal Concept (Monetary) As Of Debit ifrs-full:CurrentMaterialsAndSuppliesToBeConsumedInProductionProcessOrRenderingServices
1191 Land held under development Concept (Monetary) As Of Debit cht:LandHeldUnderDevelopment
1192 Construction in progress Concept (Monetary) As Of Debit ifrs-full:ConstructionInProgress
1193 Inventories Concept (Monetary) As Of Debit ifrs-full:Inventories
1194 101120 - Disclosure - Inventories - Additional Information (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureInventoriesAdditionalInformationDetail
1195 Implied Table Table

*

*

 implied:Table
1196 Classes Of Inventories [Abstract] Abstract ifrs-full:ClassesOfInventoriesAbstract
1197 Operating costs related to inventories Concept (Monetary) For Period Debit cht:CostOfInventoriesRecognizedAsCostDuringPeriod
1198 Provision for inventory and obsolescence Concept (Monetary) For Period ifrs-full:InventoryWritedown2011
1199 Inventory to be recovered longer than twelve months Concept (Monetary) As Of Debit cht:InventoryToBeRecoveredLongerThanTwelveMonths
1200 101130 - Disclosure - Prepayments - Summary of Prepayments (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosurePrepaymentsSummaryOfPrepaymentsDetail
1201 Implied Table Table

*

*

 implied:Table
1202 Prepayments [Abstract] Abstract cht:PrepaymentsAbstract
1203 Prepaid rents Concept (Monetary) As Of Debit cht:PrepaidRents
1204 Others Concept (Monetary) As Of Debit cht:OtherPrepayments
1205 Prepayments Concept (Monetary) As Of Debit ifrs-full:Prepayments
1206 Prepaid rents Concept (Monetary) As Of Debit cht:CurrentPrepaidRents
1207 Others Concept (Monetary) As Of Debit cht:OtherCurrentPrepayments
1208 Current prepayments Concept (Monetary) As Of Debit ifrs-full:CurrentPrepayments
1209 Prepaid rents Concept (Monetary) As Of Debit cht:NoncurrentPrepaidRents
1210 Others Concept (Monetary) As Of Debit cht:OtherNoncurrentPrepayments
1211 Noncurrent prepayments Concept (Monetary) As Of Debit ifrs-full:NoncurrentPrepayments
1212 101140 - Disclosure - Other Current Monetary Assets - Summary of Other Current Monetary Assets (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureOtherCurrentMonetaryAssetsSummaryOfOtherCurrentMonetaryAssetsDetail
1213 Implied Table Table

*

*

 implied:Table
1214 Disclosure Of Other Current Monetary Assets [Abstract] Abstract cht:DisclosureOfOtherCurrentMonetaryAssetsAbstract
1215 Time deposits and negotiable certificates of deposit with maturities of more than three months Concept (Monetary) As Of Debit ifrs-full:ShorttermDepositsNotClassifiedAsCashEquivalents
1216 Others Concept (Monetary) As Of Debit cht:MiscellaneousOtherCurrentMonetaryAssets
1217 Other current monetary assets Concept (Monetary) As Of Debit ifrs-full:OtherCurrentFinancialAssets
1218 101150 - Disclosure - Other Current Monetary Assets - Annual Yield Rates of Time Deposits and Negotiable Certificates of Deposits with Maturities of more Than Three Months (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureOtherCurrentMonetaryAssetsAnnualYieldRatesOfTimeDepositsAndNegotiableCertificatesOfDepositsWithMaturitiesOfMoreThanThreeMonthsDetail
1219 Disclosure Of Annual Yield Rates Of Other Current Monetary Assets [Table] Table

*

*

 cht:DisclosureOfAnnualYieldRatesOfOtherCurrentMonetaryAssetsTable
1220 Range [axis] Axis ifrs-full:RangeAxis
1221 Ranges [member] Member ifrs-full:RangesMember
1222 Bottom of range [Member] Member ifrs-full:BottomOfRangeMember
1223 Top of Range [Member] Member ifrs-full:TopOfRangeMember
1224 Disclosure of annual yield rates of other current monetary assets [Line Items] LineItems cht:DisclosureOfAnnualYieldRatesOfOtherCurrentMonetaryAssetsLineItems
1225 Time deposits and negotiable certificates of deposit with maturities of more than three months Concept (Percent) As Of cht:TimeDepositsAndNegotiableCertificatesOfDepositYield
1226 101160 - Disclosure - Subsidiaries - Less Than Wholly Owned Subsidiaries of the Company That Have Material Noncontrolling Interests (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureSubsidiariesLessThanWhollyOwnedSubsidiariesOfCompanyThatHaveMaterialNoncontrollingInterestsDetail
1227 Disclosure Of Significant Investments In Subsidiaries [Table] Table

*

*

 ifrs-full:DisclosureOfSignificantInvestmentsInSubsidiariesTable
1228 Subsidiaries [axis] Axis ifrs-full:SignificantInvestmentsInSubsidiariesAxis
1229 Entity's total for subsidiaries [member] Member ifrs-full:EntitysTotalForSubsidiariesMember
1230 Senao International Co., Ltd. (SENAO) [Member] Member cht:SenaoInternationalCoLtdMember
1231 Chunghwa Precision Test Tech. Co., Ltd. (CHPT) [Member] Member cht:ChunghwaPrecisionTestTechCoLtdMember
1232 Individually immaterial subsidiaries with noncontrolling interests [Member] Member cht:IndividuallyImmaterialSubsidiariesWithNoncontrollingInterestsMember
1233 Disclosure of subsidiaries [Line Items] LineItems ifrs-full:DisclosureOfSignificantInvestmentsInSubsidiariesLineItems
1234 Place of Incorporation Concept (Text/String) For Period ifrs-full:CountryOfIncorporationOrResidenceOfSubsidiary
1235 Principal Place of Business Concept (Text/String) For Period ifrs-full:PrincipalPlaceOfBusinessOfSubsidiary
1236 Proportion of Ownership Interests Held by Noncontrolling Interests Concept (Percent) For Period ifrs-full:ProportionOfOwnershipInterestsHeldByNoncontrollingInterests
1237 Proportion of Voting Rights Held by Noncontrolling Interests Concept (Percent) For Period ifrs-full:ProportionOfVotingRightsHeldByNoncontrollingInterests
1238 Profit Allocated to Noncontrolling Interests Concept (Monetary) For Period Credit ifrs-full:ProfitLossAttributableToNoncontrollingInterests
1239 Accumulated Noncontrolling Interests Concept (Monetary) As Of Credit ifrs-full:NoncontrollingInterests
1240 101170 - Disclosure - Subsidiaries - Summarized Financial Information Before Intercompany Eliminations (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureSubsidiariesSummarizedFinancialInformationBeforeIntercompanyEliminationsDetail
1241 Disclosure Of Significant Investments In Subsidiaries [Table] Table

*

*

 ifrs-full:DisclosureOfSignificantInvestmentsInSubsidiariesTable
1242 Subsidiaries [axis] Axis ifrs-full:SignificantInvestmentsInSubsidiariesAxis
1243 Entity's total for subsidiaries [member] Member ifrs-full:EntitysTotalForSubsidiariesMember
1244 Senao International Co., Ltd. (SENAO) [Member] Member cht:SenaoInternationalCoLtdMember
1245 Chunghwa Precision Test Tech. Co., Ltd. (CHPT) [Member] Member cht:ChunghwaPrecisionTestTechCoLtdMember
1246 Disclosure of subsidiaries [Line Items] LineItems ifrs-full:DisclosureOfSignificantInvestmentsInSubsidiariesLineItems
1247 Current assets Concept (Monetary) As Of Debit ifrs-full:CurrentAssets
1248 Noncurrent assets Concept (Monetary) As Of Debit ifrs-full:NoncurrentAssets
1249 Current liabilities Concept (Monetary) As Of Credit ifrs-full:CurrentLiabilities
1250 Noncurrent liabilities Concept (Monetary) As Of Credit ifrs-full:NoncurrentLiabilities
1251 Equity attributable to the parent Concept (Monetary) As Of Credit ifrs-full:EquityAttributableToOwnersOfParent
1252 NONCONTROLLING INTERESTS Concept (Monetary) As Of Credit ifrs-full:NoncontrollingInterests
1253 Revenue and income Concept (Monetary) For Period Credit cht:RevenueOtherIncomeAndOtherGains
1254 Costs and expenses Concept (Monetary) For Period Debit cht:ExpenseCostAndLoss
1255 NET INCOME Concept (Monetary) For Period Credit ifrs-full:ProfitLoss
1256 Profit attributable to the parent Concept (Monetary) For Period Credit ifrs-full:ProfitLossAttributableToOwnersOfParent
1257 Profit attributable to noncontrolling interests Concept (Monetary) For Period Credit ifrs-full:ProfitLossAttributableToNoncontrollingInterests
1258 Other comprehensive income (loss) attributable to the parent Concept (Monetary) For Period Credit ifrs-full:OtherComprehensiveIncomeAttributableToOwnersOfParent
1259 Other comprehensive loss attributable to noncontrolling interests Concept (Monetary) For Period Credit ifrs-full:OtherComprehensiveIncomeAttributableToNoncontrollingInterests
1260 Other comprehensive loss for the year Concept (Monetary) For Period Credit ifrs-full:OtherComprehensiveIncome
1261 Total comprehensive income attributable to the parent Concept (Monetary) For Period Credit ifrs-full:ComprehensiveIncomeAttributableToOwnersOfParent
1262 Total comprehensive income attributable to noncontrolling interests Concept (Monetary) For Period Credit ifrs-full:ComprehensiveIncomeAttributableToNoncontrollingInterests
1263 TOTAL COMPREHENSIVE INCOME Concept (Monetary) For Period Credit ifrs-full:ComprehensiveIncome
1264 Dividends paid to noncontrolling interests Concept (Monetary) For Period Credit ifrs-full:DividendsPaidToNoncontrollingInterests
1265 Net cash flow from operating activities Concept (Monetary) For Period ifrs-full:CashFlowsFromUsedInOperatingActivities
1266 Net cash flow from investing activities Concept (Monetary) For Period Debit ifrs-full:CashFlowsFromUsedInInvestingActivities
1267 Net cash flow from financing activities Concept (Monetary) For Period Debit ifrs-full:CashFlowsFromUsedInFinancingActivities
1268 EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS Concept (Monetary) For Period Debit ifrs-full:EffectOfExchangeRateChangesOnCashAndCashEquivalents
1269 Net cash inflow (outflow) Concept (Monetary) For Period Debit ifrs-full:IncreaseDecreaseInCashAndCashEquivalents
1270 101180 - Disclosure - Subsidiaries - Additional Information (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureSubsidiariesAdditionalInformationDetail
1271 Disclosure Of Significant Investments In Subsidiaries [Table] Table

*

*

 ifrs-full:DisclosureOfSignificantInvestmentsInSubsidiariesTable
1272 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
1273 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
1274 Chunghwa Investment Co., Ltd. (CHI) [Member] Member cht:ChunghwaInvestmentCoLtdMember
1275 Chunghwa Telecom Co., Ltd. and Chunghwa Investment Co., Ltd. (CHI) [Member] Member cht:ChunghwaTelecomCoLtdAndChunghwaInvestmentCoLtdMember
1276 Senao International Co., Ltd. (SENAO) [Member] Member cht:SenaoInternationalCoLtdMember
1277 Subsidiaries [axis] Axis ifrs-full:SignificantInvestmentsInSubsidiariesAxis
1278 Entity's total for subsidiaries [member] Member ifrs-full:EntitysTotalForSubsidiariesMember
1279 Chunghwa Precision Test Tech. Co., Ltd. (CHPT) [Member] Member cht:ChunghwaPrecisionTestTechCoLtdMember
1280 CHIEF Telecom Inc. (CHIEF) [Member] Member cht:CHIEFTelecomIncMember
1281 Senao International Co., Ltd. (SENAO) [Member] Member cht:SenaoInternationalCoLtdMember
1282 Youth Co., Ltd. (Youth) [Member] Member cht:YouthCoLtdMember
1283 Disclosure of subsidiaries [Line Items] LineItems ifrs-full:DisclosureOfSignificantInvestmentsInSubsidiariesLineItems
1284 Equity ownership percentage Concept (Percent) As Of cht:PercentageOfOwnershipInterestInSubsidiary
1285 101190 - Disclosure - Subsidiaries - Detailed Information of Equity Transactions (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureSubsidiariesDetailedInformationOfEquityTransactionsDetail
1286 Disclosure Of Classes Of Share Capital [Table] Table

*

*

 ifrs-full:DisclosureOfClassesOfShareCapitalTable
1287 Classes of share capital [axis] Axis ifrs-full:ClassesOfShareCapitalAxis
1288 Share capital [member] Member ifrs-full:ClassesOfShareCapitalMember
1289 Chunghwa Investment Co Ltd Disposed Some Shares Of Chunghwa Precision Test Tech Co Ltd Member cht:ChunghwaInvestmentCoLtdDisposedSomeSharesOfChunghwaPrecisionTestTechCoLtdMember
1290 Chunghwa Investment Co Ltd Did Not Participate In The Capital Increase Of Chunghwa Precision Test Tech Co Ltd [Member] Member cht:ChunghwaInvestmentCoLtdDidNotParticipateInTheCapitalIncreaseOfChunghwaPrecisionTestTechCoLtdMember
1291 Senao International Co Ltd Transferred Its Treasury Stock [Member] Member cht:SenaoInternationalCoLtdTransferredItsTreasuryStockMember
1292 Chunghwa Telecom Co Ltd and Chunghwa Investment Co Ltd Disposed Some Shares of CHIEF Telecom Inc [Member] Member cht:ChunghwaTelecomCoLtdAndChunghwaInvestmentCoLtdDisposedSomeSharesOfCHIEFTelecomIncMember
1293 SENAO not Proportionately participating in the Capital Increase of Youth [Member] Member cht:SenaoInternationalCoLtdNotProportionatelyParticipatingInTheCapitalIncreaseOfYouthCoLtdMember
1294 Chunghwa Telecom Co Ltd and Chunghwa Investment Co Ltd Did Not Participate in the Capital Increase of CHIEF Telecom Inc [Member] Member cht:ChunghwaTelecomCoLtdAndChunghwaInvestmentCoLtdDidNotParticipateInTheCapitalIncreaseOfCHIEFTelecomIncMember
1295 Share-Based Payment of CHIEF Telecom Inc [Member] Member cht:ShareBasedPaymentOfCHIEFTelecomIncMember
1296 Disclosure Of Classes Of Share Capital [Line Items] LineItems ifrs-full:DisclosureOfClassesOfShareCapitalLineItems
1297 Cash consideration received from (paid to)Noncontrolling interests Concept (Monetary) For Period Credit ifrs-full:ConsiderationPaidReceived
1298 The proportionate share of the carrying amount of the net assets of the subsidiary transferred (to) from noncontrolling interests Concept (Monetary) For Period Debit cht:ProportionateShareOfTheCarryingAmountOfTheNetAssetsOfTheSubsidiaryTransferredToFromNoncontrollingInterests
1299 Differences arising from equity transactions Concept (Monetary) For Period Credit ifrs-full:ChangesInEquity
1300 Additional paid-in capital - difference between consideration received or paid and the carrying amount of the subsidiaries? net assets upon actual disposal or acquisition Concept (Monetary) As Of Credit cht:DifferenceBetweenConsiderationReceivedOrPaidAndCarryingAmountOfSubsidiariesNetAssetsUponActualDisposalOrAcquisitionEffectOnAdditionalPaidinCapital
1301 Additional paid-in capital - arising from changes in equities of subsidiaries Concept (Monetary) As Of Credit cht:ChangesInEquitiesOfSubsidiariesEffectOnAdditionalPaidinCapital
1302 Unappropriated earnings Concept (Monetary) As Of Credit cht:UnappropriatedEarnings
1303 101200 - Disclosure - Investments Accounted for Using Equity Method - Summary of Investments Accounted for Using Equity Method (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureInvestmentsAccountedForUsingEquityMethodSummaryOfInvestmentsAccountedForUsingEquityMethodDetail
1304 Implied Table Table

*

*

 implied:Table
1305 Disclosure Of Significant Investments In Associates And Joint Ventures [Abstract] Abstract cht:DisclosureOfSignificantInvestmentsInAssociatesAndJointVenturesAbstract
1306 Investments in associates Concept (Monetary) As Of Debit ifrs-full:InvestmentsInAssociatesAccountedForUsingEquityMethod
1307 Investments in joint ventures Concept (Monetary) As Of Debit ifrs-full:InvestmentsInJointVenturesAccountedForUsingEquityMethod
1308 Investments accounted for using equity method Concept (Monetary) As Of Debit ifrs-full:InvestmentAccountedForUsingEquityMethod
1309 101210 - Disclosure - Investments Accounted For Using Equity Method - Additional Information (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureInvestmentsAccountedForUsingEquityMethodAdditionalInformationDetail
1310 Disclosure Of Significant Investments In Associates And Joint Ventures [Table] Table

*

*

 cht:DisclosureOfSignificantInvestmentsInAssociatesAndJointVenturesTable
1311 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
1312 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
1313 Benefit One Asia Pte Ltd [Member] Member cht:BenefitOneAsiaPteLtdMember
1314 HopeTech Technologies Limited [Member] Member cht:HopeTechTechnologiesLimitedMember
1315 Chunghwa PChome Fund I Co., Ltd. (“CPFI”) [Member] Member cht:ChunghwaPChomeFundICoLtdMember
1316 Cornerstone Ventures Co., Ltd. (“CVC”) [Member] Member cht:CornerstoneVenturesCoLtdCVCMember
1317 Associates [axis] Axis ifrs-full:SignificantInvestmentsInAssociatesAxis
1318 Entity's total for associates [member] Member ifrs-full:EntitysTotalForAssociatesMember
1319 KingwayTek Technology Co., Ltd. ("KWT") [Member] Member cht:KingwayTekTechnologyCoLtdMember
1320 Taiwan International Ports Logistics Corporation ("TIPL") [Member] Member cht:TaiwanInternationalPortsLogisticsCorporationMember
1321 Dian Zuan Integrating Marketing Co., Ltd. ("DZIM") [Member] Member cht:DianZuanIntegratingMarketingCoLtdMember
1322 Click Force Co., Ltd. ("CF") [Member] Member cht:ClickForceCoLtdMember
1323 Alliance Digital Tech Co., Ltd. ("ADT") [Member] Member cht:AllianceDigitalTechCoLtdMember
1324 Xiamen Sertec Business Technology Co., Ltd. [Member] Member cht:XiamenSertecBusinessTechnologyCoLtdMember
1325 MeWorks LIMITED (HK) ("MeWorks") [Member] Member cht:MeWorksLIMITEDHKMember
1326 UUPON Inc [member] Member cht:UUPONIncMember
1327 Subsidiaries [axis] Axis ifrs-full:SignificantInvestmentsInSubsidiariesAxis
1328 Entity's total for subsidiaries [member] Member ifrs-full:EntitysTotalForSubsidiariesMember
1329 Senao International Co., Ltd. (SENAO) [Member] Member cht:SenaoInternationalCoLtdMember
1330 Joint ventures [axis] Axis ifrs-full:JointVenturesAxis
1331 Entity's total for joint ventures [member] Member ifrs-full:EntitysTotalForJointVenturesMember
1332 Huada Digital Corporation ("HDD") [Member] Member cht:HuadaDigitalCorporationMember
1333 Chunghwa Benefit One Co., Ltd. ("CBO") [Member] Member cht:ChunghwaBenefitOneCoLtdMember
1334 Disclosure Of Significant Investments In Associates And Joint Ventures [Line Items] LineItems cht:DisclosureOfSignificantInvestmentsInAssociatesAndJointVenturesLineItems
1335 Ownership interest in associates Concept (Percent) For Period ifrs-full:ProportionOfOwnershipInterestInAssociate
1336 Investments in cash in associates Concept (Monetary) For Period Debit cht:InvestmentsInCashInAssociates
1337 Proceeds From Capital Reduction Concept (Monetary) For Period Debit cht:ProceedsFromCapitalReduction
1338 Proceeds from disposal of shares Concept (Monetary) For Period Debit ifrs-full:ProceedsFromSalesOfInterestsInAssociates
1339 Losses on disposals recognized Concept (Monetary) For Period Debit ifrs-full:LossesOnDisposalsOfInvestments
1340 Percentage of ownership in associates Concept (Percent) As Of cht:PercentageOfOwnershipInterestInAssociate
1341 No Of Seats Allotted Concept (Integer) For Period cht:NumberOfSeatsAllotted
1342 Number Of Seats Available For Board Of Directors Concept (Integer) For Period cht:NumberOfSeatsAvailableForBoardOfDirectors
1343 101220 - Disclosure - Investments Accounted for Using Equity Method - Investments in Associates (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureInvestmentsAccountedForUsingEquityMethodInvestmentsInAssociatesDetail
1344 Disclosure Of Significant Investments In Associates [Table] Table

*

*

 ifrs-full:DisclosureOfSignificantInvestmentsInAssociatesTable
1345 Associates [axis] Axis ifrs-full:SignificantInvestmentsInAssociatesAxis
1346 Entity's total for associates [member] Member ifrs-full:EntitysTotalForAssociatesMember
1347 Senao Networks, Inc. ("SNI") [Member] Member cht:SenaoNetworksIncMember
1348 ST-2 Satellite Ventures Pte., Ltd. ("STS") [Member] Member cht:ST2SatelliteVenturesPteLtdMember
1349 International Integrated System, Inc. ("IISI") [Member] Member cht:InternationalIntegratedSystemIncMember
1350 Viettel-CHT Co., Ltd. ("Viettel-CHT") [Member] Member cht:ViettelCHTCoLtdMember
1351 Taiwan International Standard Electronics Co., Ltd. ("TISE") [Member] Member cht:TaiwanInternationalStandardElectronicsCoLtdMember
1352 Chunghwa PChome Fund I Co., Ltd. (“CPFI”) [Member] Member cht:ChunghwaPChomeFundICoLtdMember
1353 KKBOX Taiwan Co., Ltd. (“KKBOXTW”) [Member] Member cht:KKBOXTaiwanCoLtdMember
1354 KingwayTek Technology Co., Ltd. ("KWT") [Member] Member cht:KingwayTekTechnologyCoLtdMember
1355 So-net Entertainment Taiwan Limited ("So-net") [Member] Member cht:SonetEntertainmentTaiwanLimitedMember
1356 Taiwan International Ports Logistics Corporation ("TIPL") [Member] Member cht:TaiwanInternationalPortsLogisticsCorporationMember
1357 Click Force Co., Ltd. ("CF") [Member] Member cht:ClickForceCoLtdMember
1358 Alliance Digital Tech Co., Ltd. ("ADT") [Member] Member cht:AllianceDigitalTechCoLtdMember
1359 UUPON Inc [member] Member cht:UUPONIncMember
1360 HopeTech Technologies Limited [Member] Member cht:HopeTechTechnologiesLimitedMember
1361 Cornerstone Ventures Co., Ltd. (“CVC”) [Member] Member cht:CornerstoneVenturesCoLtdMember
1362 MeWorks LIMITED (HK) ("MeWorks") [Member] Member cht:MeWorksLIMITEDHKMember
1363 Associates [Member] Member ifrs-full:AssociatesMember
1364 Disclosure of associates [Line Items] LineItems ifrs-full:DisclosureOfSignificantInvestmentsInAssociatesLineItems
1365 Investments in associates Concept (Monetary) As Of Debit ifrs-full:InvestmentsInAssociatesAccountedForUsingEquityMethod
1366 Percentage of ownership in associates Concept (Percent) As Of cht:PercentageOfOwnershipInterestInAssociate
1367 Percentage of voting rights in associates Concept (Percent) As Of cht:PercentageOfVotingPowerHeldInAssociate
1368 The Company’s share of profits (loss) Concept (Monetary) For Period Credit ifrs-full:ShareOfProfitLossOfAssociatesAndJointVenturesAccountedForUsingEquityMethod
1369 The Company’s share of other comprehensive income (loss) Concept (Monetary) For Period Credit ifrs-full:ShareOfOtherComprehensiveIncomeOfAssociatesAndJointVenturesAccountedForUsingEquityMethod
1370 The Company’s share of total comprehensive income (loss) Concept (Monetary) For Period Credit ifrs-full:ShareOfTotalComprehensiveIncomeOfAssociatesAndJointVenturesAccountedForUsingEquityMethod
1371 Fair values based on the closing market prices of SNI Concept (Monetary) As Of Debit ifrs-full:FairValueOfInvestmentsInAssociatesWherePriceQuotationsPublished
1372 101230 - Disclosure - Investments Accounted for Using Equity Method - Investments in Joint Ventures (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureInvestmentsAccountedForUsingEquityMethodInvestmentsInJointVenturesDetail
1373 Disclosure Of Joint Ventures [Table] Table

*

*

 ifrs-full:DisclosureOfJointVenturesTable
1374 Joint ventures [axis] Axis ifrs-full:JointVenturesAxis
1375 Entity's total for joint ventures [member] Member ifrs-full:EntitysTotalForJointVenturesMember
1376 Joint ventures [Member] Member ifrs-full:JointVenturesMember
1377 Disclosure of joint ventures [Line Items] LineItems ifrs-full:DisclosureOfJointVenturesLineItems
1378 The Company’s share of profits (loss) Concept (Monetary) For Period Credit ifrs-full:ShareOfProfitLossOfAssociatesAndJointVenturesAccountedForUsingEquityMethod
1379 The Company’s share of other comprehensive income (loss) Concept (Monetary) For Period Credit ifrs-full:ShareOfOtherComprehensiveIncomeOfAssociatesAndJointVenturesAccountedForUsingEquityMethod
1380 The Company’s share of total comprehensive income (loss) Concept (Monetary) For Period Credit ifrs-full:ShareOfTotalComprehensiveIncomeOfAssociatesAndJointVenturesAccountedForUsingEquityMethod
1381 101240 - Disclosure - Property, Plant and Equipment - Summary of Property, Plant and Equipment (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosurePropertyPlantAndEquipmentSummaryOfPropertyPlantAndEquipmentDetail
1382 Disclosure Of Property Plant And Equipment [Table] Table

*

*

 ifrs-full:DisclosureOfPropertyPlantAndEquipmentTable
1383 Classes of property, plant and equipment [axis] Axis ifrs-full:ClassesOfPropertyPlantAndEquipmentAxis
1384 Property, plant and equipment [member] Member ifrs-full:PropertyPlantAndEquipmentMember
1385 Land [Member] Member ifrs-full:LandMember
1386 Land improvements [Member] Member cht:LandImprovements1Member
1387 Buildings [Member] Member ifrs-full:BuildingsMember
1388 Computer equipment [Member] Member ifrs-full:ComputerEquipmentMember
1389 Telecommunications equipment [Member] Member ifrs-full:CommunicationAndNetworkEquipmentMember
1390 Transportation equipment [Member] Member ifrs-full:VehiclesMember
1391 Miscellaneous equipment [Member] Member cht:MiscellaneousEquipmentMember
1392 Construction in progress and equipment to be accepted [Member] Member ifrs-full:ConstructionInProgressMember
1393 Carrying amount, accumulated depreciation, amortisation and impairment and gross carrying amount [axis] Axis ifrs-full:CarryingAmountAccumulatedDepreciationAmortisationAndImpairmentAndGrossCarryingAmountAxis
1394 Carrying amount [member] Member ifrs-full:CarryingAmountMember
1395 Gross carrying amount [Member] Member ifrs-full:GrossCarryingAmountMember
1396 Accumulated depreciation, amortization and impairment [Member] Member ifrs-full:AccumulatedDepreciationAmortisationAndImpairmentMember
1397 Disclosure of detailed information about property, plant and equipment [Line Items] LineItems ifrs-full:DisclosureOfPropertyPlantAndEquipmentLineItems
1398 Beginning balance Concept (Monetary) As Of Debit ifrs-full:PropertyPlantAndEquipment
1399 Depreciation expenses Concept (Monetary) For Period ifrs-full:DepreciationPropertyPlantAndEquipment
1400 Additions Concept (Monetary) For Period Debit ifrs-full:AdditionsOtherThanThroughBusinessCombinationsPropertyPlantAndEquipment
1401 Disposal Concept (Monetary) For Period Credit ifrs-full:DisposalsPropertyPlantAndEquipment
1402 Impairment losses Concept (Monetary) For Period ifrs-full:ImpairmentLossRecognisedInProfitOrLossPropertyPlantAndEquipment
1403 Effect of foreign exchange differences Concept (Monetary) For Period Debit ifrs-full:IncreaseDecreaseThroughNetExchangeDifferencesPropertyPlantAndEquipment
1404 Acquisitions through business combinations Concept (Monetary) For Period Debit ifrs-full:AcquisitionsThroughBusinessCombinationsPropertyPlantAndEquipment
1405 Others Concept (Monetary) For Period Debit ifrs-full:IncreaseDecreaseThroughOtherChangesPropertyPlantAndEquipment
1406 Ending balance Concept (Monetary) As Of Debit ifrs-full:PropertyPlantAndEquipment
1407 101250 - Disclosure - Property, Plant and Equipment - Additional Information (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosurePropertyPlantAndEquipmentAdditionalInformationDetail
1408 Disclosure Of Property Plant And Equipment [Table] Table

*

*

 ifrs-full:DisclosureOfPropertyPlantAndEquipmentTable
1409 Classes of property, plant and equipment [axis] Axis ifrs-full:ClassesOfPropertyPlantAndEquipmentAxis
1410 Property, plant and equipment [member] Member ifrs-full:PropertyPlantAndEquipmentMember
1411 Telecommunications equipment [Member] Member ifrs-full:CommunicationAndNetworkEquipmentMember
1412 Partial computer and miscellaneous equipment [Member] Member cht:PartialComputerAndMiscellaneousEquipmentMember
1413 Disclosure of detailed information about property, plant and equipment [Line Items] LineItems ifrs-full:DisclosureOfPropertyPlantAndEquipmentLineItems
1414 Impairment losses Concept (Monetary) For Period ifrs-full:ImpairmentLossRecognisedInProfitOrLossPropertyPlantAndEquipment
1415 101260 - Disclosure - Property, Plant and Equipment - Estimated Service Lives of Property, Plant and Equipment (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosurePropertyPlantAndEquipmentEstimatedServiceLivesOfPropertyPlantAndEquipmentDetail
1416 Disclosure Of Property Plant And Equipment [Table] Table

*

*

 ifrs-full:DisclosureOfPropertyPlantAndEquipmentTable
1417 Classes of property, plant and equipment [axis] Axis ifrs-full:ClassesOfPropertyPlantAndEquipmentAxis
1418 Property, plant and equipment [member] Member ifrs-full:PropertyPlantAndEquipmentMember
1419 Land improvements [Member] Member cht:LandImprovements1Member
1420 Main buildings [Member] Member cht:MainBuildingsMember
1421 Other building facilities [Member] Member cht:OtherBuildingFacilitiesMember
1422 Computer equipment [Member] Member ifrs-full:ComputerEquipmentMember
1423 Telecommunication circuits [Member] Member cht:TelecommunicationCircuitsMember
1424 Telecommunication machinery and antennas equipment [Member] Member cht:TelecommunicationMachineryAndAntennasEquipmentMember
1425 Transportation equipment [Member] Member ifrs-full:VehiclesMember
1426 Leasehold improvements [Member] Member ifrs-full:LeaseholdImprovementsMember
1427 Mechanical and air conditioner equipment [Member] Member cht:MechanicalAndAirConditionerEquipmentMember
1428 Others [Member] Member ifrs-full:OtherPropertyPlantAndEquipmentMember
1429 Range [axis] Axis ifrs-full:RangeAxis
1430 Ranges [member] Member ifrs-full:RangesMember
1431 Bottom of Range [Member] Member ifrs-full:BottomOfRangeMember
1432 Top of Range [Member] Member ifrs-full:TopOfRangeMember
1433 Disclosure of detailed information about property, plant and equipment [Line Items] LineItems ifrs-full:DisclosureOfPropertyPlantAndEquipmentLineItems
1434 Estimated service lives Concept (Text/String) For Period ifrs-full:UsefulLivesOrDepreciationRatesPropertyPlantAndEquipment
1435 101270 - Disclosure - Investment Properties - Summary of Investment Properties (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureInvestmentPropertiesSummaryOfInvestmentPropertiesDetail
1436 Disclosure Of Investment Property [Table] Table

*

*

 ifrs-full:DisclosureOfInvestmentPropertyTable
1437 Carrying amount, accumulated depreciation, amortisation and impairment and gross carrying amount [axis] Axis ifrs-full:CarryingAmountAccumulatedDepreciationAmortisationAndImpairmentAndGrossCarryingAmountAxis
1438 Carrying amount [member] Member ifrs-full:CarryingAmountMember
1439 Gross carrying amount [Member] Member ifrs-full:GrossCarryingAmountMember
1440 Accumulated depreciation, amortization and impairment [Member] Member ifrs-full:AccumulatedDepreciationAmortisationAndImpairmentMember
1441 Disclosure of detailed information about investment property [Line Items] LineItems ifrs-full:DisclosureOfInvestmentPropertyLineItems
1442 Beginning balance Concept (Monetary) As Of Debit ifrs-full:InvestmentProperty
1443 Depreciation expense Concept (Monetary) For Period ifrs-full:DepreciationInvestmentProperty
1444 Additions Concept (Monetary) For Period Debit ifrs-full:AdditionsOtherThanThroughBusinessCombinationsInvestmentProperty
1445 Disposal Concept (Monetary) For Period Credit ifrs-full:DisposalsInvestmentProperty
1446 Reclassification Concept (Monetary) For Period Debit ifrs-full:TransferFromToInventoriesAndOwnerOccupiedPropertyInvestmentProperty
1447 Reversal of impairment loss Concept (Monetary) For Period ifrs-full:ReversalOfImpairmentLossRecognisedInProfitOrLossInvestmentProperty
1448 Ending balance Concept (Monetary) As Of Debit ifrs-full:InvestmentProperty
1449 101280 - Disclosure - Investment Properties - Estimated Service Lives of Investment Properties (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureInvestmentPropertiesEstimatedServiceLivesOfInvestmentPropertiesDetail
1450 Disclosure Of Investment Property [Table] Table

*

*

 ifrs-full:DisclosureOfInvestmentPropertyTable
1451 Types of investment property [axis] Axis ifrs-full:TypesOfInvestmentPropertyAxis
1452 Investment property [member] Member ifrs-full:InvestmentPropertyMember
1453 Land improvements [Member] Member cht:LandImprovements1Member
1454 Main buildings [Member] Member cht:MainBuildingsMember
1455 Other building facilities [Member] Member cht:OtherBuildingFacilitiesMember
1456 Range [axis] Axis ifrs-full:RangeAxis
1457 Ranges [member] Member ifrs-full:RangesMember
1458 Bottom of range [Member] Member ifrs-full:BottomOfRangeMember
1459 Top of Range [Member] Member ifrs-full:TopOfRangeMember
1460 Disclosure of detailed information about investment property [Line Items] LineItems ifrs-full:DisclosureOfInvestmentPropertyLineItems
1461 Estimated service lives Concept (Text/String) For Period ifrs-full:UsefulLivesOrDepreciationRatesInvestmentPropertyCostModel
1462 101290 - Disclosure - Investment Properties - Additional Information (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureInvestmentPropertiesAdditionalInformationDetail
1463 Implied Table Table

*

*

 implied:Table
1464 Disclosure Of Investment Property [Abstract] Abstract ifrs-full:DisclosureOfInvestmentPropertyAbstract
1465 Reversal of impairment loss Concept (Monetary) For Period ifrs-full:ReversalOfImpairmentLossRecognisedInProfitOrLossInvestmentProperty
1466 101300 - Disclosure - Investment Properties - Key Assumptions and Fair Values of Investment Properties (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureInvestmentPropertiesKeyAssumptionsAndFairValuesOfInvestmentPropertiesDetail
1467 Disclosure Of Investment Property [Table] Table

*

*

 ifrs-full:DisclosureOfInvestmentPropertyTable
1468 Measurement [axis] Axis ifrs-full:MeasurementAxis
1469 Aggregated measurement [member] Member ifrs-full:AggregatedMeasurementMember
1470 At fair value [Member] Member ifrs-full:AtFairValueMember
1471 Range [axis] Axis ifrs-full:RangeAxis
1472 Ranges [member] Member ifrs-full:RangesMember
1473 Bottom of range [Member] Member ifrs-full:BottomOfRangeMember
1474 Top of Range [Member] Member ifrs-full:TopOfRangeMember
1475 Disclosure of detailed information about investment property [Line Items] LineItems ifrs-full:DisclosureOfInvestmentPropertyLineItems
1476 Investment properties Concept (Monetary) As Of Debit ifrs-full:InvestmentProperty
1477 Overall capital interest rate Concept (Percent) For Period cht:CapitalInterestRate
1478 Profit margin ratio Concept (Percent) For Period cht:ProfitMarginRatio
1479 Discount rate Concept (Percent) For Period cht:DiscountRateOnInvestmentProperties
1480 Capitalization rate Concept (Percent) For Period cht:InvestmentPropertyCapitalizationRates
1481 101310 - Disclosure - Intangible Assets - Summary of Intangible Assets (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureIntangibleAssetsSummaryOfIntangibleAssetsDetail
1482 Disclosure Of Intangible Assets [Table] Table

*

*

 ifrs-full:DisclosureOfIntangibleAssetsTable
1483 Classes of intangible assets and goodwill [axis] Axis ifrs-full:ClassesOfIntangibleAssetsAndGoodwillAxis
1484 Intangible assets and goodwill [member] Member ifrs-full:IntangibleAssetsAndGoodwillMember
1485 3G and 4G concession [Member] Member ifrs-full:LicencesAndFranchisesMember
1486 Computer software [Member] Member ifrs-full:ComputerSoftwareMember
1487 Goodwill [Member] Member ifrs-full:GoodwillMember
1488 Others [Member] Member ifrs-full:OtherIntangibleAssetsMember
1489 Carrying amount, accumulated depreciation, amortisation and impairment and gross carrying amount [axis] Axis ifrs-full:CarryingAmountAccumulatedDepreciationAmortisationAndImpairmentAndGrossCarryingAmountAxis
1490 Carrying amount [member] Member ifrs-full:CarryingAmountMember
1491 Gross carrying amount [Member] Member ifrs-full:GrossCarryingAmountMember
1492 Accumulated depreciation, amortization and impairment [Member] Member ifrs-full:AccumulatedDepreciationAmortisationAndImpairmentMember
1493 Disclosure of detailed information about intangible assets [Line Items] LineItems ifrs-full:DisclosureOfIntangibleAssetsLineItems
1494 Beginning balance Concept (Monetary) As Of Debit ifrs-full:IntangibleAssetsAndGoodwill
1495 Additions-acquired separately Concept (Monetary) For Period Debit ifrs-full:AdditionsOtherThanThroughBusinessCombinationsIntangibleAssetsOtherThanGoodwill
1496 Amortization expenses Concept (Monetary) For Period ifrs-full:AmortisationIntangibleAssetsOtherThanGoodwill
1497 Disposal Concept (Monetary) For Period Credit ifrs-full:DisposalsIntangibleAssetsAndGoodwill
1498 Impairment losses Concept (Monetary) For Period ifrs-full:ImpairmentLossRecognisedInProfitOrLossIntangibleAssetsAndGoodwill
1499 Effect of foreign exchange difference Concept (Monetary) For Period Debit ifrs-full:IncreaseDecreaseThroughNetExchangeDifferencesIntangibleAssetsAndGoodwill
1500 Others Concept (Monetary) For Period Debit ifrs-full:IncreaseDecreaseThroughOtherChangesIntangibleAssetsAndGoodwill
1501 Ending balance Concept (Monetary) As Of Debit ifrs-full:IntangibleAssetsAndGoodwill
1502 Acquisitions through business combinations Concept (Monetary) For Period Debit ifrs-full:AcquisitionsThroughBusinessCombinationsIntangibleAssetsAndGoodwill
1503 101320 - Disclosure - Intangible Assets - Additional Information (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureIntangibleAssetsAdditionalInformationDetail
1504 Disclosure Of Intangible Assets [Table] Table

*

*

 ifrs-full:DisclosureOfIntangibleAssetsTable
1505 Classes of intangible assets other than goodwill [axis] Axis ifrs-full:ClassesOfIntangibleAssetsOtherThanGoodwillAxis
1506 Intangible assets other than goodwill [member] Member ifrs-full:IntangibleAssetsOtherThanGoodwillMember
1507 Computer software [Member] Member ifrs-full:ComputerSoftwareMember
1508 Others [Member] Member ifrs-full:OtherIntangibleAssetsMember
1509 Range [axis] Axis ifrs-full:RangeAxis
1510 Ranges [member] Member ifrs-full:RangesMember
1511 Bottom of range [Member] Member ifrs-full:BottomOfRangeMember
1512 Top of Range [Member] Member ifrs-full:TopOfRangeMember
1513 Associates [axis] Axis ifrs-full:SignificantInvestmentsInAssociatesAxis
1514 Entity's total for associates [member] Member ifrs-full:EntitysTotalForAssociatesMember
1515 Senao Networks, Inc. ("SNI") [Member] Member cht:SenaoNetworksIncMember
1516 Classes of assets [axis] Axis ifrs-full:ClassesOfAssetsAxis
1517 Assets [member] Member ifrs-full:ClassesOfAssetsMember
1518 Goodwill [Member] Member ifrs-full:GoodwillMember
1519 Certain licensed contract [Member] Member cht:LicensedContractMember
1520 Disclosure of detailed information about intangible assets [Line Items] LineItems ifrs-full:DisclosureOfIntangibleAssetsLineItems
1521 4G concession fees Concept (Monetary) For Period Debit ifrs-full:AdditionsOtherThanThroughBusinessCombinationsIntangibleAssetsOtherThanGoodwill
1522 Estimated useful lives Concept (Text/String) For Period ifrs-full:UsefulLivesOrAmortisationRatesIntangibleAssetsOtherThanGoodwill
1523 Discount rate Concept (Percent) For Period cht:DiscountRate
1524 Impairment loss Concept (Monetary) For Period Debit ifrs-full:ImpairmentLossRecognisedInProfitOrLoss
1525 101330 - Disclosure - Other Assets - Summary of Other Assets (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureOtherAssetsSummaryOfOtherAssetsDetail
1526 Implied Table Table

*

*

 implied:Table
1527 Miscellaneous Assets [Abstract] Abstract ifrs-full:MiscellaneousAssetsAbstract
1528 Spare parts Concept (Monetary) As Of Debit ifrs-full:SpareParts
1529 Refundable deposits Concept (Monetary) As Of Debit ifrs-full:LongtermDeposits
1530 Other financial assets Concept (Monetary) As Of Debit ifrs-full:OtherNoncurrentFinancialAssets
1531 Others Concept (Monetary) As Of Debit ifrs-full:OtherNonfinancialAssets
1532 Other assets Concept (Monetary) As Of Debit ifrs-full:OtherAssets
1533 Others Concept (Monetary) As Of Debit ifrs-full:OtherCurrentNonfinancialAssets
1534 Other current assets Concept (Monetary) As Of Debit ifrs-full:OtherCurrentAssets
1535 Others Concept (Monetary) As Of Debit ifrs-full:OtherNoncurrentNonfinancialAssets
1536 Other noncurrent assets Concept (Monetary) As Of Debit ifrs-full:OtherNoncurrentAssets
1537 101340 - Disclosure - Hedging Derivative Financial Instruments - Summary of Hedging Derivative Financial Instruments (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureHedgingDerivativeFinancialInstrumentsSummaryOfHedgingDerivativeFinancialInstrumentsDetail
1538 Disclosure Of Detailed Information About Hedging Instruments [Table] Table

*

*

 ifrs-full:DisclosureOfDetailedInformationAboutHedgingInstrumentsTable
1539 Types of hedges [axis] Axis ifrs-full:TypesOfHedgesAxis
1540 Hedges [member] Member ifrs-full:TypesOfHedgesMember
1541 Cash flow hedges [member] Member ifrs-full:CashFlowHedgesMember
1542 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
1543 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
1544 Forward exchange contracts [Member] Member ifrs-full:ForwardContractMember
1545 Disclosure Of Detailed Information About Hedging Instruments [Line Items] LineItems ifrs-full:DisclosureOfDetailedInformationAboutHedgingInstrumentsLineItems
1546 Cash flow hedge - forward exchange contracts Concept (Monetary) As Of Debit ifrs-full:DerivativeFinancialAssets
1547 Cash flow hedge-forward exchange contracts, financial liabilities Concept (Monetary) As Of Credit ifrs-full:DerivativeFinancialLiabilities
1548 101350 - Disclosure - Hedging Derivative Financial Instruments - Additional Information (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureHedgingDerivativeFinancialInstrumentsAdditionalInformationDetail
1549 Implied Table Table

*

*

 implied:Table
1550 Disclosure Of Detailed Information About Hedging Instruments [Abstract] Abstract ifrs-full:DisclosureOfDetailedInformationAboutHedgingInstrumentsAbstract
1551 Gains (losses) on change in value of forward elements of forward contracts, net of tax Concept (Monetary) For Period Credit ifrs-full:GainsLossesOnChangeInValueOfForwardElementsOfForwardContractsNetOfTax
1552 Reclassification of gain (loss) arising from forward exchange contracts Concept (Monetary) For Period Debit ifrs-full:ReclassificationAdjustmentsOnChangeInValueOfForwardElementsOfForwardContractsNetOfTax
1553 101360 - Disclosure - Hedging Derivative Financial Instruments - Outstanding Forward Exchange Contracts (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureHedgingDerivativeFinancialInstrumentsOutstandingForwardExchangeContractsDetail
1554 Disclosure Of Detailed Information About Hedging Instruments [Table] Table

*

*

 ifrs-full:DisclosureOfDetailedInformationAboutHedgingInstrumentsTable
1555 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
1556 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
1557 Forward exchange contracts [Member] Member ifrs-full:ForwardContractMember
1558 Types of hedges [axis] Axis ifrs-full:TypesOfHedgesAxis
1559 Hedges [member] Member ifrs-full:TypesOfHedgesMember
1560 Cash flow hedges [member] Member ifrs-full:CashFlowHedgesMember
1561 Disclosure Of Detailed Information About Hedging Instruments [Line Items] LineItems ifrs-full:DisclosureOfDetailedInformationAboutHedgingInstrumentsLineItems
1562 Currency Concept (Text/String) For Period cht:DerivativeContractCrossCurrency
1563 Maturity Period Concept (Text/String) For Period cht:DescriptionOfDerivativeFinancialInstrumentsMaturityPeriod
1564 Contract Amount Concept (Monetary) As Of invest:DerivativeNotionalAmount
1565 101370 - Disclosure - 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) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureHedgingDerivativeFinancialInstrumentsLossGainArisingFromHedgingDerivativeFinancialInstrumentsThatHaveBeenReclassifiedFromEquityToInitialCostOfPropertyPlantAndEquipmentDetail
1566 Implied Table Table

*

*

 implied:Table
1567 Disclosure Of Detailed Information About Hedging Instruments [Abstract] Abstract ifrs-full:DisclosureOfDetailedInformationAboutHedgingInstrumentsAbstract
1568 Construction in progress and equipment to be accepted Concept (Monetary) For Period Debit cht:LossGainArisingFromHedgingDerivativeFinancialInstrumentsReclassifiedFromEquityToInitialCostOfPropertyPlantAndEquipment
1569 101380 - Disclosure - Hedging Derivative Financial Instruments - Summary of Hedging Instrument (Details) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureHedgingDerivativeFinancialInstrumentsSummaryOfHedgingInstrumentDetails
1570 Disclosure Of Detailed Information About Hedging Instruments [Table] Table

*

*

 ifrs-full:DisclosureOfDetailedInformationAboutHedgingInstrumentsTable
1571 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
1572 Risks [member] Member ifrs-full:TypesOfRisksMember
1573 Foreign currency risk [Member] Member ifrs-full:CurrencyRiskMember
1574 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
1575 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
1576 Forecast Purchases - forward Exchange Contract [Member] Member cht:ForecastPurchasesForwardExchangeContractsMember
1577 Types of hedges [axis] Axis ifrs-full:TypesOfHedgesAxis
1578 Hedges [member] Member ifrs-full:TypesOfHedgesMember
1579 Cash flow hedges [member] Member ifrs-full:CashFlowHedgesMember
1580 Disclosure Of Detailed Information About Hedging Instruments [Line Items] LineItems ifrs-full:DisclosureOfDetailedInformationAboutHedgingInstrumentsLineItems
1581 Currency Concept (Text/String) For Period cht:DerivativeContractCrossCurrency
1582 Contract Amount Concept (Monetary) As Of invest:DerivativeNotionalAmount
1583 Maturity Period Concept (Text/String) For Period cht:DescriptionOfDerivativeFinancialInstrumentsMaturityPeriod
1584 Forward Rate Concept (Decimal) For Period cht:DerivativeForwardRate
1585 Carrying Amount of Asset Concept (Monetary) As Of Debit ifrs-full:DerivativeFinancialAssets
1586 Cash flow hedge-forward exchange contracts, financial liabilities Concept (Monetary) As Of Credit ifrs-full:DerivativeFinancialLiabilities
1587 Change in Fair Values of Hedging Instruments Used for Calculating Hedge Ineffectiveness Concept (Monetary) For Period Credit ifrs-full:GainLossOnChangeInFairValueOfHedgingInstrumentUsedAsBasisForRecognisingHedgeIneffectiveness
1588 Change in Value of Hedged Item Used for Calculating Hedge Ineffectiveness Concept (Monetary) For Period Credit cht:GainLossOnChangeInValueOfHedgingInstrumentUsedAsBasisForRecognisingHedgeIneffectiveness
1589 Accumulated Gain or Loss on Hedging Instruments in Other Equity Continuing Hedges Concept (Monetary) For Period Credit cht:AccumulatedGainOrLossOnHedgingInstrumentsInOtherEquityContinuingHedges
1590 Accumulated Gain or Loss on Hedging Instruments in Other Equity Hedge Accounting No Longer Applied Concept (Monetary) For Period Credit cht:AccumulatedGainOrLossOnHedgingInstrumentsInOtherEquityHedgeAccountingNoLongerApplied
1591 101390 - Disclosure - Hedging Derivative Financial Instruments - Summary of Hedging Transaction and Reclassification Affected Comprehensive Income (Details) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureHedgingDerivativeFinancialInstrumentsSummaryOfHedgingTransactionAndReclassificationAffectedComprehensiveIncomeDetails
1592 Disclosure Of Reclassification Of Financial Assets [Table] Table

*

*

 ifrs-full:DisclosureOfReclassificationOfFinancialAssetsTable
1593 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
1594 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
1595 Forecast Purchases - forward Exchange Contract [Member] Member cht:ForecastPurchasesForwardExchangeContractsMember
1596 Types of hedges [axis] Axis ifrs-full:TypesOfHedgesAxis
1597 Hedges [member] Member ifrs-full:TypesOfHedgesMember
1598 Cash flow hedges [member] Member ifrs-full:CashFlowHedgesMember
1599 Disclosure Of Reclassification Of Financial Assets [Line Items] LineItems ifrs-full:DisclosureOfReclassificationOfFinancialAssetsLineItems
1600 Hedging Gain or Loss Recognized in OCI Concept (Monetary) For Period Credit ifrs-full:GainLossOnHedgeIneffectivenessRecognisedInOtherComprehensiveIncome
1601 Change in Fair Values of Hedging Instruments Used for Calculating Hedge Ineffectiveness Concept (Monetary) For Period Credit ifrs-full:GainLossOnChangeInFairValueOfHedgingInstrumentUsedAsBasisForRecognisingHedgeIneffectiveness
1602 Amount Reclassified to P/L and the Adjusted Line Item Concept (Monetary) For Period Credit ifrs-full:ReclassificationOutOfFinancialAssetsAtFairValueThroughProfitOrLoss
1603 Due to Hedged Future Cash Flows No Longer Expected to Occur Concept (Monetary) For Period Debit ifrs-full:ReclassificationAdjustmentsOnCashFlowHedgesForWhichHedgedFutureCashFlowsAreNoLongerExpectedToOccurNetOfTax
1604 101400 - Disclosure - Short Term Loans - Summary of Short-term Loans (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureShortTermLoansSummaryOfShortTermLoansDetail
1605 Disclosure Of Detailed Information About Borrowings [Table] Table

*

*

 ifrs-full:DisclosureOfDetailedInformationAboutBorrowingsTable
1606 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
1607 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
1608 Short-term loans [Member] Member cht:ShorttermLoansMember
1609 Borrowings by name [axis] Axis ifrs-full:BorrowingsByNameAxis
1610 Borrowings by name [member] Member ifrs-full:BorrowingsByNameMember
1611 Unsecured loans [Member] Member cht:UnsecuredLoansMember
1612 Range [axis] Axis ifrs-full:RangeAxis
1613 Ranges [member] Member ifrs-full:RangesMember
1614 Bottom of Range [Member] Member ifrs-full:BottomOfRangeMember
1615 Top of Range [Member] Member ifrs-full:TopOfRangeMember
1616 Disclosure of detailed information about borrowings [Line Items] LineItems ifrs-full:DisclosureOfDetailedInformationAboutBorrowingsLineItems
1617 Unsecured loans Concept (Monetary) As Of Credit ifrs-full:UnsecuredBankLoansReceived
1618 Interest rates of loans Concept (Percent) As Of ifrs-full:BorrowingsInterestRate
1619 101410 - Disclosure - Long Term Loans - Summary of Long-term Loans (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureLongTermLoansSummaryOfLongTermLoansDetail
1620 Disclosure Of Detailed Information About Borrowings [Table] Table

*

*

 ifrs-full:DisclosureOfDetailedInformationAboutBorrowingsTable
1621 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
1622 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
1623 Long-term loans [Member] Member cht:LongTermLoansMember
1624 Borrowings by name [axis] Axis ifrs-full:BorrowingsByNameAxis
1625 Borrowings by name [member] Member ifrs-full:BorrowingsByNameMember
1626 Secured loans [Member] Member cht:SecuredLoansMember
1627 Disclosure of detailed information about borrowings [Line Items] LineItems ifrs-full:DisclosureOfDetailedInformationAboutBorrowingsLineItems
1628 Secured loans Concept (Monetary) As Of Credit ifrs-full:SecuredBankLoansReceived
1629 Interest rates of loans Concept (Percent) As Of ifrs-full:BorrowingsInterestRate
1630 101420 - Disclosure - Long Term Loans - Additional Information (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureLongTermLoansAdditionalInformationDetail
1631 Disclosure Of Detailed Information About Borrowings [Table] Table

*

*

 ifrs-full:DisclosureOfDetailedInformationAboutBorrowingsTable
1632 Subsidiaries [axis] Axis ifrs-full:SignificantInvestmentsInSubsidiariesAxis
1633 Entity's total for subsidiaries [member] Member ifrs-full:EntitysTotalForSubsidiariesMember
1634 Light Era Development Co., Ltd. (LED) [Member] Member cht:LightEraDevelopmentCoLtdMember
1635 Borrowings by name [axis] Axis ifrs-full:BorrowingsByNameAxis
1636 Borrowings by name [member] Member ifrs-full:BorrowingsByNameMember
1637 Chang Hwa Bank Secured Loan [Member] Member cht:ChangHwaBankSecuredLoanMember
1638 Maturity [axis] Axis ifrs-full:MaturityAxis
1639 Aggregated time bands [member] Member ifrs-full:AggregatedTimeBandsMember
1640 Extended Due September 2021 [Member] Member cht:ExtendedDueSeptember2021Member
1641 Due December 2014 [Member] Member cht:DueDecember2014Member
1642 Due September 2015 [Member] Member cht:DueSeptember2015Member
1643 Disclosure of detailed information about borrowings [Line Items] LineItems ifrs-full:DisclosureOfDetailedInformationAboutBorrowingsLineItems
1644 Secured loan Concept (Monetary) As Of Credit ifrs-full:SecuredBankLoansReceived
1645 Early repayment of secured loan Concept (Monetary) For Period Credit cht:RepaymentOfSecuredLoans
1646 Loan due date Concept (Text/String) For Period ifrs-full:BorrowingsMaturity
1647 101430 - Disclosure - Trade Notes and Accounts Payable - Summary of Trade Notes and Accounts Payable (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureTradeNotesAndAccountsPayableSummaryOfTradeNotesAndAccountsPayableDetail
1648 Implied Table Table

*

*

 implied:Table
1649 Trade And Other Current Payables [Abstract] Abstract ifrs-full:TradeAndOtherCurrentPayablesAbstract
1650 Trade notes and accounts payable Concept (Monetary) As Of Credit ifrs-full:TradeAndOtherCurrentPayablesToTradeSuppliers
1651 101440 - Disclosure - Other Payables - Summary of Other Payables (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureOtherPayablesSummaryOfOtherPayablesDetail
1652 Implied Table Table

*

*

 implied:Table
1653 Trade And Other Current Payables [Abstract] Abstract ifrs-full:TradeAndOtherCurrentPayablesAbstract
1654 Accrued salary and compensation Concept (Monetary) As Of Credit ifrs-full:ShorttermEmployeeBenefitsAccruals
1655 Accrued compensation to employees and remuneration to directors and supervisors Concept (Monetary) As Of Credit cht:AccruedCompensationToEmployeesAndRemunerationToDirectorsAndSupervisors
1656 Payables to contractors Concept (Monetary) As Of Credit cht:PayablesToContractors
1657 Payables to equipment suppliers Concept (Monetary) As Of Credit cht:CurrentPayablesForPurchaseOfEquipment
1658 Amounts collected for others Concept (Monetary) As Of Credit cht:AmountsCollectedForOthers
1659 Accrued franchise fees Concept (Monetary) As Of Credit cht:AccruedFranchiseFees
1660 Accrued maintenance costs Concept (Monetary) As Of Credit cht:AccruedMaintenanceCosts
1661 Others Concept (Monetary) As Of Credit cht:MiscellaneousOtherCurrentPayables
1662 Total Concept (Monetary) As Of Credit ifrs-full:OtherCurrentPayables
1663 101450 - Disclosure - Provisions - Summary of Provisions (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureProvisionsSummaryOfProvisionsDetail
1664 Implied Table Table

*

*

 implied:Table
1665 Provisions [Abstract] Abstract ifrs-full:ProvisionsAbstract
1666 Warranties Concept (Monetary) As Of Credit ifrs-full:WarrantyProvision
1667 Employee benefits Concept (Monetary) As Of Credit ifrs-full:ProvisionsForEmployeeBenefits
1668 Trade-in right Concept (Monetary) As Of Credit cht:ProvisionsForTradeInRight
1669 Others Concept (Monetary) As Of Credit ifrs-full:MiscellaneousOtherProvisions
1670 Provisions Concept (Monetary) As Of Credit ifrs-full:Provisions
1671 Current Concept (Monetary) As Of Credit ifrs-full:CurrentProvisions
1672 Noncurrent Concept (Monetary) As Of Credit ifrs-full:NoncurrentProvisions
1673 101470 - Disclosure - Provisions - Movements in Provisions (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureProvisionsMovementsInProvisionsDetail
1674 Disclosure Of Other Provisions [Table] Table

*

*

 ifrs-full:DisclosureOfOtherProvisionsTable
1675 Classes of other provisions [axis] Axis ifrs-full:ClassesOfProvisionsAxis
1676 Other provisions [member] Member ifrs-full:OtherProvisionsMember
1677 Warranties [Member] Member ifrs-full:WarrantyProvisionMember
1678 Employee benefits [Member] Member cht:EmploymentBenefitsProvisionMember
1679 Trade-in rights [Member] Member cht:TradeInRightsProvisionMember
1680 Others [Member] Member ifrs-full:MiscellaneousOtherProvisionsMember
1681 Disclosure of other provisions [Line Items] LineItems ifrs-full:DisclosureOfOtherProvisionsLineItems
1682 Beginning balance Concept (Monetary) As Of Credit ifrs-full:Provisions
1683 Effect of retrospective application of IFRS 15 Concept (Monetary) As Of Debit cht:IncreaseDecreaseInProvisionDueToRetrospectiveApplicationOfIFRS15
1684 Additional provisions recognized Concept (Monetary) For Period Credit cht:AdditionalProvisionRecognized
1685 Used / forfeited during the year Concept (Monetary) For Period Debit cht:ProvisionsUsed
1686 Ending balance Concept (Monetary) As Of Credit ifrs-full:Provisions
1687 Beginning balance as adjusted Concept (Monetary) As Of Credit cht:ProvisionsAsAdjusted
1688 101480 - Disclosure - Retirement Benefit Plans - Additional Information (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureRetirementBenefitPlansAdditionalInformationDetail
1689 Disclosure Of Defined Retirement Plan [Table] Table

*

*

 cht:DisclosureOfDefinedRetirementPlanTable
1690 Range [axis] Axis ifrs-full:RangeAxis
1691 Ranges [member] Member ifrs-full:RangesMember
1692 Top of range [Member] Member ifrs-full:TopOfRangeMember
1693 Bottom of Range [Member] Member ifrs-full:BottomOfRangeMember
1694 Disclosure of Defined Retirement Plans LineItems cht:DisclosureOfDefinedRetirementPlanLineItems
1695 Percentage of monthly salaries and wages contributed to employees' individual pension accounts Concept (Percent) As Of cht:PercentageOfSalariesAndWagesContributedToEmployeesDefinedContributionPlans
1696 Defined benefit plan contribution, percentage Concept (Percent) For Period cht:DefinedBenefitPlansEmployerContributionPercentage
1697 101490 - Disclosure - Retirement Benefit Plans - Amounts Included in Consolidated Balance Sheets from Obligation in Respect of Defined Benefit Plans (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureRetirementBenefitPlansAmountsIncludedInConsolidatedBalanceSheetsFromObligationInRespectOfDefinedBenefitPlansDetail
1698 Implied Table Table

*

*

 implied:Table
1699 Disclosure Of Defined Benefit Plans [Abstract] Abstract ifrs-full:DisclosureOfDefinedBenefitPlansAbstract
1700 Present value of funded defined benefit obligation Concept (Monetary) As Of Credit ifrs-full:DefinedBenefitObligationAtPresentValue
1701 Fair value of plan assets Concept (Monetary) As Of Debit ifrs-full:PlanAssetsAtFairValue
1702 Funded status - deficit Concept (Monetary) As Of Debit ifrs-full:SurplusDeficitInPlan
1703 Net defined benefit liabilities Concept (Monetary) As Of Credit ifrs-full:NoncurrentRecognisedLiabilitiesDefinedBenefitPlan
1704 Net defined benefit assets Concept (Monetary) As Of Debit ifrs-full:NoncurrentRecognisedAssetsDefinedBenefitPlan
1705 Defined benefit obligation Concept (Monetary) As Of Credit ifrs-full:LiabilityAssetOfDefinedBenefitPlans
1706 101500 - Disclosure - Retirement Benefit Plans - Movements in Defined Benefit Obligation and Fair Value of Plan Assets (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureRetirementBenefitPlansMovementsInDefinedBenefitObligationAndFairValueOfPlanAssetsDetail
1707 Disclosure Of Defined Benefit Plans [Table] Table

*

*

 ifrs-full:DisclosureOfDefinedBenefitPlansTable
1708 Net defined benefit liability (asset) [axis] Axis ifrs-full:NetDefinedBenefitLiabilityAssetAxis
1709 Net defined benefit liability (asset) [member] Member ifrs-full:NetDefinedBenefitLiabilityAssetMember
1710 Present value of funded defined benefit obligation [Member] Member ifrs-full:PresentValueOfDefinedBenefitObligationMember
1711 Fair value of plan assets [Member] Member ifrs-full:PlanAssetsMember
1712 Disclosure Of Defined Plan [line items] LineItems ifrs-full:DisclosureOfDefinedBenefitPlansLineItems
1713 Net defined benefit liability (asset) at beginning of period Concept (Monetary) As Of Credit ifrs-full:LiabilityAssetOfDefinedBenefitPlans
1714 Current service cost Concept (Monetary) For Period Credit ifrs-full:CurrentServiceCostNetDefinedBenefitLiabilityAsset
1715 Interest expense/interest income Concept (Monetary) For Period Credit ifrs-full:InterestExpenseIncomeNetDefinedBenefitLiabilityAsset
1716 Amounts recognized in profit or loss Concept (Monetary) For Period Debit cht:DefinedBenefitCostRecognizedInProfitOrLoss
1717 Remeasurement on the net defined benefit liability Abstract ifrs-full:GainLossOnRemeasurementOfNetDefinedBenefitLiabilityAssetAbstract
1718 Return on plan assets (excluding amounts included in net interest) Concept (Monetary) For Period Debit ifrs-full:ReturnOnPlanAssetsNetDefinedBenefitLiabilityAsset
1719 Actuarial (gain) losses recognized from changes in demographic assumptions Concept (Monetary) For Period Debit ifrs-full:ActuarialGainsLossesArisingFromChangesInDemographicAssumptionsNetDefinedBenefitLiabilityAsset
1720 Actuarial (gains) losses recognized from changes in financial assumptions Concept (Monetary) For Period Debit ifrs-full:ActuarialGainsLossesArisingFromChangesInFinancialAssumptionsNetDefinedBenefitLiabilityAsset
1721 Actuarial losses recognized from experience adjustments Concept (Monetary) For Period Debit ifrs-full:ActuarialGainsLossesArisingFromExperienceAdjustmentsNetDefinedBenefitLiabilityAsset
1722 Amounts recognized in other comprehensive income Concept (Monetary) For Period Credit ifrs-full:OtherComprehensiveIncomeBeforeTaxGainsLossesOnRemeasurementsOfDefinedBenefitPlans
1723 Contributions from employer Concept (Monetary) For Period Debit ifrs-full:ContributionsToPlanByEmployerNetDefinedBenefitLiabilityAsset
1724 Benefits paid Concept (Monetary) For Period Debit cht:BenefitsPaid
1725 Benefits paid directly by the Company Concept (Monetary) For Period Debit cht:BenefitsPaidDirectlyByEmployer
1726 Net defined benefit liability (asset) at end of period Concept (Monetary) As Of Credit ifrs-full:LiabilityAssetOfDefinedBenefitPlans
1727 101510 - Disclosure - Retirement Benefit Plans - Pension Costs Recognized in Profit and Loss for Defined Benefit Plans (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureRetirementBenefitPlansPensionCostsRecognizedInProfitAndLossForDefinedBenefitPlansDetail
1728 Disclosure Of Defined Benefit Plans [Table] Table

*

*

 ifrs-full:DisclosureOfDefinedBenefitPlansTable
1729 Statement Of Comprehensive Income Profit Or Loss Location Axis cht:StatementOfComprehensiveIncomeProfitOrLossLocationAxis
1730 Income Statement Locations Member cht:IncomeStatementLocationsDomain
1731 Operating costs [Member] Member cht:OperatingCostsMember
1732 Marketing expenses [Member] Member cht:MarketingExpensesMember
1733 General and administrative expenses [Member] Member cht:GeneralAndAdministrativeExpensesMember
1734 Research and development expenses [Member] Member cht:ResearchAndDevelopmentExpensesMember
1735 Disclosure Of Defined Plan [line items] LineItems ifrs-full:DisclosureOfDefinedBenefitPlansLineItems
1736 Defined benefit plans pension costs recognized in profit and loss Concept (Monetary) For Period Debit ifrs-full:PostemploymentBenefitExpenseDefinedBenefitPlans
1737 101520 - Disclosure - Retirement Benefit Plans - Principal Assumptions Used for Actuarial Valuations (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureRetirementBenefitPlansPrincipalAssumptionsUsedForActuarialValuationsDetail
1738 Disclosure Of Defined Benefit Plans [Table] Table

*

*

 ifrs-full:DisclosureOfDefinedBenefitPlansTable
1739 Range [axis] Axis ifrs-full:RangeAxis
1740 Ranges [member] Member ifrs-full:RangesMember
1741 Bottom of range [Member] Member ifrs-full:BottomOfRangeMember
1742 Top of range [Member] Member ifrs-full:TopOfRangeMember
1743 Disclosure Of Defined Plan [line items] LineItems ifrs-full:DisclosureOfDefinedBenefitPlansLineItems
1744 Discount rates Concept (Percent) As Of ifrs-full:ActuarialAssumptionOfDiscountRates
1745 Expected rates of salary increase Concept (Percent) As Of ifrs-full:ActuarialAssumptionOfExpectedRatesOfSalaryIncreases
1746 101530 - Disclosure - Retirement Benefit Plans - Effect on Present Value of Defined Benefit Obligation Due to a Reasonably Possible Change of the Significant Actuarial Assumptions (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureRetirementBenefitPlansEffectOnPresentValueOfDefinedBenefitObligationDueToReasonablyPossibleChangeOfSignificantActuarialAssumptionsDetail
1747 Disclosure Of Sensitivity Analysis For Actuarial Assumptions [Table] Table

*

*

 ifrs-full:DisclosureOfSensitivityAnalysisForActuarialAssumptionsTable
1748 Actuarial assumptions [axis] Axis ifrs-full:ActuarialAssumptionsAxis
1749 Actuarial assumptions [member] Member ifrs-full:ActuarialAssumptionsMember
1750 Discount rates [Member] Member ifrs-full:ActuarialAssumptionOfDiscountRatesMember
1751 Expected rates of salary increases [Member] Member ifrs-full:ActuarialAssumptionOfExpectedRatesOfSalaryIncreasesMember
1752 Disclosure of sensitivity analysis for actuarial assumptions [Line Items] LineItems ifrs-full:DisclosureOfSensitivityAnalysisForActuarialAssumptionsLineItems
1753 0.5% increase Concept (Monetary) As Of Credit ifrs-full:IncreaseDecreaseInDefinedBenefitObligationDueToReasonablyPossibleIncreaseInActuarialAssumption
1754 0.5% decrease Concept (Monetary) As Of Credit ifrs-full:IncreaseDecreaseInDefinedBenefitObligationDueToReasonablyPossibleDecreaseInActuarialAssumption
1755 101540 - Disclosure - Retirement Benefit Plans - Effect on Present Value of Defined Benefit Obligation Due to a Reasonably Possible Change of the Significant Actuarial Assumptions (Parenthetical) (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureRetirementBenefitPlansEffectOnPresentValueOfDefinedBenefitObligationDueToReasonablyPossibleChangeOfSignificantActuarialAssumptionsParentheticalDetail
1756 Disclosure Of Sensitivity Analysis For Actuarial Assumptions [Table] Table

*

*

 ifrs-full:DisclosureOfSensitivityAnalysisForActuarialAssumptionsTable
1757 Actuarial assumptions [axis] Axis ifrs-full:ActuarialAssumptionsAxis
1758 Actuarial assumptions [member] Member ifrs-full:ActuarialAssumptionsMember
1759 Discount rates [Member] Member ifrs-full:ActuarialAssumptionOfDiscountRatesMember
1760 Expected rates of salary increases [Member] Member ifrs-full:ActuarialAssumptionOfExpectedRatesOfSalaryIncreasesMember
1761 Disclosure of sensitivity analysis for actuarial assumptions [Line Items] LineItems ifrs-full:DisclosureOfSensitivityAnalysisForActuarialAssumptionsLineItems
1762 Percentage increase in actuarial assumptions Concept (Percent) As Of ifrs-full:PercentageOfReasonablyPossibleIncreaseInActuarialAssumption
1763 Percentage decrease in actuarial assumptions Concept (Percent) As Of ifrs-full:PercentageOfReasonablyPossibleDecreaseInActuarialAssumption
1764 101550 - Disclosure - Retirement Benefit Plans - Summary of Sensitivity Analysis (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureRetirementBenefitPlansSummaryOfSensitivityAnalysisDetail
1765 Disclosure Of Sensitivity Analysis For Actuarial Assumptions [Table] Table

*

*

 ifrs-full:DisclosureOfSensitivityAnalysisForActuarialAssumptionsTable
1766 Range [axis] Axis ifrs-full:RangeAxis
1767 Ranges [member] Member ifrs-full:RangesMember
1768 Bottom of range [Member] Member ifrs-full:BottomOfRangeMember
1769 Top of range [Member] Member ifrs-full:TopOfRangeMember
1770 Disclosure of sensitivity analysis for actuarial assumptions [Line Items] LineItems ifrs-full:DisclosureOfSensitivityAnalysisForActuarialAssumptionsLineItems
1771 The expected contributions to the plan for the next year Concept (Monetary) For Period Credit ifrs-full:EstimateOfContributionsExpectedToBePaidToPlan
1772 The average duration of the defined benefit obligation Concept (Decimal) For Period ifrs-full:WeightedAverageDurationOfDefinedBenefitObligation
1773 101560 - Disclosure - Retirement Benefit Plans - Maturity Analysis of Undiscounted Benefit Payments (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureRetirementBenefitPlansMaturityAnalysisOfUndiscountedBenefitPaymentsDetail
1774 Implied Table Table

*

*

 implied:Table
1775 Disclosure Of Defined Benefit Plans [Abstract] Abstract ifrs-full:DisclosureOfDefinedBenefitPlansAbstract
1776 2019 Concept (Monetary) For Period Debit cht:EstimatedFutureBenefitPaymentsNextTwelveMonths
1777 2020 Concept (Monetary) For Period Debit cht:EstimatedFutureBenefitPaymentsYearTwo
1778 2021 Concept (Monetary) For Period Debit cht:EstimatedFutureBenefitPaymentsYearThree
1779 2022 Concept (Monetary) For Period Debit cht:EstimatedFutureBenefitPaymentsYearFour
1780 2023 and thereafter Concept (Monetary) For Period Debit cht:EstimatedFutureBenefitPaymentsFiveFiscalYearsThereafter
1781 Total Concept (Monetary) For Period Debit cht:EstimatedFutureBenefitPayments
1782 101570 - Disclosure - Equity - Summary of Common Stocks (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureEquitySummaryOfCommonStocksDetail
1783 Implied Table Table

*

*

 implied:Table
1784 Disclosure Of Classes Of Share Capital [Abstract] Abstract ifrs-full:DisclosureOfClassesOfShareCapitalAbstract
1785 Number of authorized shares Concept (Shares) As Of ifrs-full:NumberOfSharesAuthorised
1786 Authorized shares Concept (Monetary) As Of Credit cht:AuthorizedCapital
1787 Number of issued and paid shares Concept (Shares) As Of ifrs-full:NumberOfSharesIssuedAndFullyPaid
1788 Issued and outstanding shares Concept (Monetary) As Of Credit ifrs-full:IssuedCapital
1789 101580 - Disclosure - Equity - Additional Information (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureEquityAdditionalInformationDetail
1790 Disclosure Of Classes Of Share Capital [Table] Table

*

*

 ifrs-full:DisclosureOfClassesOfShareCapitalTable
1791 Classes of ordinary shares [axis] Axis ifrs-full:ClassesOfOrdinarySharesAxis
1792 Ordinary shares [member] Member ifrs-full:OrdinarySharesMember
1793 American Depositary Shares [Member] Member cht:AmericanDepositarySharesMember
1794 Range [axis] Axis ifrs-full:RangeAxis
1795 Ranges [member] Member ifrs-full:RangesMember
1796 Bottom of range [Member] Member ifrs-full:BottomOfRangeMember
1797 Top of Range [Member] Member ifrs-full:TopOfRangeMember
1798 Disclosure Of Classes Of Share Capital [Line Items] LineItems ifrs-full:DisclosureOfClassesOfShareCapitalLineItems
1799 Common stock par value Concept (Share) As Of ifrs-full:ParValuePerShare
1800 Number of common stocks represented by 1 ADS Concept (Shares) As Of cht:NumberOfCommonSharesForEachAmericanDepositoryShare
1801 Number of common stock outstanding Concept (Shares) As Of ifrs-full:NumberOfSharesOutstanding
1802 Number of units Concept (Integer) As Of cht:NumberOfUnits
1803 Percentage of American Depositary Shares as common stock outstanding Concept (Percent) As Of cht:PercentageOfAmericanDepositarySharesAsCommonStockOutstanding
1804 Percentage of net income allocation toward legal reserve Concept (Percent) For Period cht:PercentageOfNetIncomeAllocationTowardLegalReserve
1805 Percentage of retained earnings distributed as dividend Concept (Percent) For Period cht:PercentageOfRetainedEarningsDistributedAsDividend
1806 Dividend distributed per share threshold in the form of common stocks Concept (Share) For Period ifrs-full:DividendsRecognisedAsDistributionsToOwnersPerShare
1807 Percentage of legal reserve on additional paid in capital Concept (Percent) For Period cht:PercentageOfLegalReservesOnAdditionalPaidInCapital
1808 101590 - Disclosure - Equity - Adjustments of Additional Paid-in Capital (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureEquityAdjustmentsOfAdditionalPaidInCapitalDetail
1809 Statement Of Changes In Equity [Table] Table

*

*

 ifrs-full:StatementOfChangesInEquityTable
1810 Components of equity [axis] Axis ifrs-full:ComponentsOfEquityAxis
1811 Equity [member] Member ifrs-full:EquityMember
1812 Share premium [Member] Member ifrs-full:SharePremiumMember
1813 Movements Of Additional Paidin Capital For Associates And Joint Ventures Accounted For Using Equity Method Member cht:MovementsOfAdditionalPaidinCapitalForAssociatesAndJointVenturesAccountedForUsingEquityMethodMember
1814 Movements of additional paid-in capital arising from changes in equities of subsidiaries [Member] Member cht:MovementsOfAdditionalPaidinCapitalArisingFromChangesInEquitiesOfSubsidiariesMember
1815 Difference between consideration received and carrying amount of the subsidiaries' net assets upon disposal [Member] Member cht:DifferenceBetweenConsiderationReceivedAndCarryingAmountOfSubsidiariesNetAssetsUponDisposalMember
1816 Donated capital [Member] Member cht:DonatedCapitalMember
1817 Stockholders' contribution due to privatization [Member] Member cht:StockholdersContributionDueToPrivatizationMember
1818 Additional paid-in capital [Member] Member ifrs-full:AdditionalPaidinCapitalMember
1819 Statement Of Changes In Equity [Line Items] LineItems ifrs-full:StatementOfChangesInEquityLineItems
1820 Beginning balance Concept (Monetary) As Of Credit ifrs-full:Equity
1821 Partial disposal of interests in subsidiaries Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseThroughDisposalOfSubsidiary
1822 Unclaimed dividend Concept (Monetary) For Period Credit cht:IncreaseDecreaseThroughUnclaimedDividend
1823 Change in additional paid-in capital from investments in associates and joint ventures accounted for using equity method Concept (Monetary) For Period Credit cht:IncreaseDecreaseInAdditionalPaidinCapitalFromInvestmentsInAssociatesAndJointVenturesAccountedForUsingEquityMethod
1824 Change in additional paid-in capital for not participating proportionately in the capital increase of a subsidiary Concept (Monetary) For Period Credit cht:IncreaseDecreaseInAdditionalPaidinCapitalForNotParticipatingInCapitalIncreaseOfSubsidiary
1825 Other changes in additional paid-in capital of subsidiaries Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseThroughTransfersAndOtherChangesEquity
1826 Share-based payment transactions of subsidiaries Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseThroughSharebasedPaymentTransactions
1827 Treasury stock transfer of subsidiaries Concept (Monetary) For Period Credit cht:TransferOfTreasuryStockOfSubsidiaries
1828 Ending balance Concept (Monetary) As Of Credit ifrs-full:Equity
1829 101600 - Disclosure - Equity - Appropriations of Earnings (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureEquityAppropriationsOfEarningsDetail
1830 Statement Of Changes In Equity [Table] Table

*

*

 ifrs-full:StatementOfChangesInEquityTable
1831 Components of equity [axis] Axis ifrs-full:ComponentsOfEquityAxis
1832 Equity [member] Member ifrs-full:EquityMember
1833 Special reserve [Member] Member cht:SpecialReserveMember
1834 Cash dividends [member] Member cht:CashDividendMember
1835 Statement Of Changes In Equity [Line Items] LineItems ifrs-full:StatementOfChangesInEquityLineItems
1836 Appropriations of earnings Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseThroughAppropriationOfRetainedEarnings
1837 Reversal of special reserve Concept (Monetary) For Period Credit cht:IncreaseDecreaseThroughReversalOfSpecialReserve
1838 Cash dividends per share Concept (Share) For Period ifrs-full:DividendsProposedOrDeclaredBeforeFinancialStatementsAuthorisedForIssueButNotRecognisedAsDistributionToOwnersPerShare
1839 101610 - Disclosure - Equity - Unrealized Gain or Loss on Available-for-sale Financial Assets (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureEquityUnrealizedGainOrLossOnAvailableForSaleFinancialAssetsDetail
1840 Statement Of Changes In Equity [Table] Table

*

*

 ifrs-full:StatementOfChangesInEquityTable
1841 Components of equity [axis] Axis ifrs-full:ComponentsOfEquityAxis
1842 Equity [member] Member ifrs-full:EquityMember
1843 Unrealized gain (loss) on available-for-sale financial assets [Member] Member ifrs-full:ReserveOfGainsAndLossesOnRemeasuringAvailableforsaleFinancialAssetsMember
1844 Retrospective application and retrospective restatement [axis] Axis ifrs-full:RetrospectiveApplicationAndRetrospectiveRestatementAxis
1845 Currently stated [member] Member ifrs-full:RestatedMember
1846 IFRS 9 [Member] Member ifrs-full:InAccordanceWithIFRS9Member
1847 Statement Of Changes In Equity [Line Items] LineItems ifrs-full:StatementOfChangesInEquityLineItems
1848 Beginning balance Concept (Monetary) As Of Credit ifrs-full:Equity
1849 Unrealized gain or loss on available-for-sale financial assets Concept (Monetary) For Period Credit ifrs-full:GainsLossesOnRemeasuringAvailableforsaleFinancialAssetsBeforeTax
1850 Income tax relating to unrealized gain and loss on available-for-sale financial assets Concept (Monetary) For Period Debit ifrs-full:IncomeTaxRelatingToAvailableforsaleFinancialAssetsOfOtherComprehensiveIncome
1851 Amount reclassified from equity to profit or loss on disposal of available-for-sale financial assets Concept (Monetary) For Period Debit ifrs-full:ReclassificationAdjustmentsOnAvailableforsaleFinancialAssetsBeforeTax
1852 Amount reclassified from equity to profit or loss on impairment of available-for-sale financial assets Concept (Monetary) For Period Credit ifrs-full:ReclassificationOutOfAvailableforsaleFinancialAssets
1853 Ending balance Concept (Monetary) As Of Credit ifrs-full:Equity
1854 Effect of retrospective application of IFRS 9 Concept (Monetary) As Of Debit ifrs-full:IncreaseDecreaseInFinancialAssetsArisingFromChangeInMeasurementAttributeFirstApplicationOfIFRS9
1855 101620 - Disclosure - Equity - Unrealized Gain or Loss on Financial Assets at FVOCI (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureEquityUnrealizedGainOrLossOnFinancialAssetsAtFVOCIDetail
1856 Statement Of Changes In Equity [Table] Table

*

*

 ifrs-full:StatementOfChangesInEquityTable
1857 Retrospective application and retrospective restatement [axis] Axis ifrs-full:RetrospectiveApplicationAndRetrospectiveRestatementAxis
1858 Currently stated [member] Member ifrs-full:RestatedMember
1859 IFRS 9 [Member] Member ifrs-full:InAccordanceWithIFRS9Member
1860 Statement Of Changes In Equity [Line Items] LineItems ifrs-full:StatementOfChangesInEquityLineItems
1861 Beginning balance Concept (Monetary) As Of Credit cht:UnrealizedGainOrLossOnFinancialAssetsAtFVOCI
1862 Effect of retrospective application of IFRS 9 Concept (Monetary) As Of Debit ifrs-full:IncreaseDecreaseInFinancialAssetsArisingFromChangeInMeasurementAttributeFirstApplicationOfIFRS9
1863 Unrealized gain or loss for the year Abstract cht:UnrealizedGainOrLossForYearAbstract
1864 Equity instruments Concept (Monetary) For Period Credit cht:UnrealizedGainOrLossOnEquityInstrument
1865 Ending balance Concept (Monetary) As Of Credit cht:UnrealizedGainOrLossOnFinancialAssetsAtFVOCI
1866 101630 - Disclosure - Equity - Noncontrolling Interests (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureEquityNoncontrollingInterestsDetail
1867 Statement Of Changes In Equity [Table] Table

*

*

 ifrs-full:StatementOfChangesInEquityTable
1868 Retrospective application and retrospective restatement [axis] Axis ifrs-full:RetrospectiveApplicationAndRetrospectiveRestatementAxis
1869 Currently stated [member] Member ifrs-full:RestatedMember
1870 As Adjusted [Member] Member cht:AsAdjustedMember
1871 Components of equity [axis] Axis ifrs-full:ComponentsOfEquityAxis
1872 Equity [member] Member ifrs-full:EquityMember
1873 Noncontrolling interests [Member] Member ifrs-full:NoncontrollingInterestsMember
1874 Statement Of Changes In Equity [Line Items] LineItems ifrs-full:StatementOfChangesInEquityLineItems
1875 Beginning balance Concept (Monetary) As Of Credit ifrs-full:Equity
1876 Effect of retrospective application of IFRS 9 Concept (Monetary) As Of Debit ifrs-full:IncreaseDecreaseInFinancialAssetsArisingFromChangeInMeasurementAttributeFirstApplicationOfIFRS9
1877 Profit Allocated to Noncontrolling Interests Concept (Monetary) For Period Credit ifrs-full:ProfitLossAttributableToNoncontrollingInterests
1878 Exchange differences arising from the translation of the net investment in foreign operations Concept (Monetary) For Period Credit ifrs-full:GainsLossesOnExchangeDifferencesOnTranslationNetOfTax
1879 Unrealized gain or loss on financial assets at FVOCI Concept (Monetary) For Period Credit ifrs-full:GainsLossesOnFinancialAssetsMeasuredAtFairValueThroughOtherComprehensiveIncomeNetOfTax
1880 Unrealized gain or loss on available-for-sale financial assets Concept (Monetary) For Period Credit ifrs-full:GainsLossesOnRemeasuringAvailableforsaleFinancialAssetsBeforeTax
1881 Income tax relating to unrealized gain and loss on available-for-sale financial assets Concept (Monetary) For Period Debit ifrs-full:IncomeTaxRelatingToAvailableforsaleFinancialAssetsOfOtherComprehensiveIncome
1882 Remeasurements of defined benefit pension plans Concept (Monetary) For Period Credit ifrs-full:OtherComprehensiveIncomeNetOfTaxGainsLossesOnRemeasurementsOfDefinedBenefitPlans
1883 Income tax relating to remeasurements of defined benefit pension plans Concept (Monetary) For Period Debit ifrs-full:IncomeTaxRelatingToRemeasurementsOfDefinedBenefitPlansOfOtherComprehensiveIncome
1884 Share of other comprehensive income or loss of associates accounted for using equity method Concept (Monetary) For Period Credit ifrs-full:ShareOfOtherComprehensiveIncomeOfAssociatesAndJointVenturesAccountedForUsingEquityMethod
1885 Cash dividends distributed by subsidiaries Concept (Monetary) For Period Debit ifrs-full:DividendsRecognisedAsDistributionsToNoncontrollingInterests
1886 Partial disposal of interests in subsidiaries Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseThroughDisposalOfSubsidiary
1887 Change in additional paid-in capital for not proportionately participating in the capital increase of subsidiaries Concept (Monetary) For Period Credit cht:IncreaseDecreaseInAdditionalPaidInCapitalForNotProportionatelyParticipatingInCapitalIncreaseOfSubsidiaries
1888 Other changes in additional paid-in capital of subsidiaries Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseThroughTransfersAndOtherChangesEquity
1889 Share-based payment transactions of subsidiaries Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseThroughSharebasedPaymentTransactions
1890 Net increase in noncontrolling interests Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseThroughChangeInEquityOfSubsidiaries
1891 Ending balance Concept (Monetary) As Of Credit ifrs-full:Equity
1892 101640 - Disclosure - Revenue - Summary of Revenue (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureRevenueSummaryOfRevenueDetail
1893 Implied Table Table

*

*

 implied:Table
1894 Revenue [Abstract] Abstract ifrs-full:RevenueAbstract
1895 Revenue from contracts with customers Concept (Monetary) For Period Credit ifrs-full:RevenueFromContractsWithCustomers
1896 Other revenues Abstract cht:OtherRevenuesAbstract
1897 Rental income Concept (Monetary) For Period Credit cht:RentalIncomeFromOperatingActivities
1898 Other Concept (Monetary) For Period Credit ifrs-full:OtherIncome
1899 Revenue other than from contracts with customers Concept (Monetary) For Period Credit cht:RevenueOtherThanFromContractsWithCustomers
1900 Total Concept (Monetary) For Period Credit ifrs-full:Revenue
1901 101650 - Disclosure - Revenue - Summary of Disaggregation of Revenue (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureRevenueSummaryOfDisaggregationOfRevenueDetail
1902 Disclosure Of Disaggregation Of Revenue From Contracts With Customers [Table] Table

*

*

 ifrs-full:DisclosureOfDisaggregationOfRevenueFromContractsWithCustomersTable
1903 Products and services [axis] Axis ifrs-full:ProductsAndServicesAxis
1904 Products and services [member] Member ifrs-full:ProductsAndServicesMember
1905 Mobile services [Member] Member cht:MobileServicesMember
1906 Sales of product [Member] Member cht:SalesOfProductMember
1907 Local telephone and domestic long distance telephone services [Member] Member cht:LocalTelephoneAndDomesticLongDistanceTelephoneServicesMember
1908 Broadband access and domestic leased line services [Member] Member cht:BroadbandAccessAndDomesticLeasedLineServicesMember
1909 Data communications internet services [Member] Member cht:DataCommunicationsInternetServicesMember
1910 International network and leased telephone services [Member] Member cht:InternationalNetworkAndLeasedTelephoneServicesMember
1911 Others [Member] Member cht:OtherProductsAndServicesMember
1912 Segments [axis] Axis ifrs-full:SegmentsAxis
1913 Segments [member] Member ifrs-full:SegmentsMember
1914 Domestic Fixed Communications Business [Member] Member cht:DomesticFixedCommunicationsBusinessMember
1915 Mobile Communications Business [Member] Member cht:MobileCommunicationsBusinessMember
1916 Internet Business [Member] Member cht:InternetBusinessMember
1917 International Fixed Communications Business [Member] Member cht:InternationalFixedCommunicationsBusinessMember
1918 Other [Member] Member ifrs-full:AllOtherSegmentsMember
1919 Disclosure Of Disaggregation Of Revenue From Contracts With Customers [Line Items] LineItems ifrs-full:DisclosureOfDisaggregationOfRevenueFromContractsWithCustomersLineItems
1920 Revenue from contracts with customers Concept (Monetary) For Period Credit ifrs-full:RevenueFromContractsWithCustomers
1921 101660 - Disclosure - Revenue - Summary of Contract Balances (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureRevenueSummaryOfContractBalancesDetail
1922 Implied Table Table

*

*

 implied:Table
1923 Disclosure Of Contract Balance [Abstract] Abstract cht:DisclosureOfContractBalanceAbstract
1924 Trade notes and accounts receivable, net Concept (Monetary) As Of Debit ifrs-full:CurrentTradeReceivables
1925 Contract assets Abstract ifrs-full:ContractAssetsAbstract
1926 Products and service bundling Concept (Monetary) As Of Debit cht:ProductAndServiceBundlingOfContractsAssets
1927 Other Concept (Monetary) As Of Debit cht:OtherContractsAssets
1928 Less : Loss allowance Concept (Monetary) As Of Credit cht:AllowanceForLossOnContractAssets
1929 Contract assets Concept (Monetary) As Of Debit ifrs-full:ContractAssets
1930 Contract assets Concept (Monetary) As Of Debit ifrs-full:CurrentContractAssets
1931 Contract assets Concept (Monetary) As Of Debit ifrs-full:NoncurrentContractAssets
1932 Contract liabilities Abstract ifrs-full:ContractLiabilitiesAbstract
1933 Telecommunications business Concept (Monetary) As Of Credit cht:TelecommunicationBusinessOfContractLiabilities
1934 Project business Concept (Monetary) As Of Credit cht:ProjectBusinessOfContractLiabilities
1935 Products and service bundling Concept (Monetary) As Of Credit cht:ProductAndServiceBundlingOfContractsLiabilities
1936 Other Concept (Monetary) As Of Credit cht:OtherContractLiabilities
1937 Contract liabilities Concept (Monetary) As Of Credit ifrs-full:ContractLiabilities
1938 Current Contract Liabilities Concept (Monetary) As Of Credit ifrs-full:CurrentContractLiabilities
1939 Noncurrent Contract Liabilities Concept (Monetary) As Of Credit ifrs-full:NoncurrentContractLiabilities
1940 Contract liabilities Concept (Monetary) As Of Credit ifrs-full:ContractLiabilities
1941 101680 - Disclosure - Revenue - Summary of Changes in Contract Assets and Contract Liabilities (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureRevenueSummaryOfChangesInContractAssetsAndContractLiabilitiesDetail
1942 Implied Table Table

*

*

 implied:Table
1943 Revenue From Contract With Customer [Abstract] Abstract us-gaap:RevenueFromContractWithCustomerAbstract
1944 Contract assets Abstract ifrs-full:ContractAssetsAbstract
1945 Net increase of customer contracts Concept (Monetary) For Period Debit cht:IncreaseInContractAssetThroughIncreaseInCustomerContracts
1946 Reclassified to trade receivables Concept (Monetary) For Period Credit cht:DecreaseInContractAssetThroughReclassificationToTradeReceivables
1947 Significant changes of contract assets Concept (Monetary) For Period Debit cht:SignificantChangesOfContractAssets
1948 Contract liabilities Abstract ifrs-full:ContractLiabilitiesAbstract
1949 Net increase of customer contracts Concept (Monetary) For Period Credit cht:IncreaseInContractLiabilitiesThroughIncreaseInCustomerContracts
1950 Recognized as revenues Concept (Monetary) For Period Debit cht:DecreaseInContractLiabilitiesRevenueRecognition
1951 Significant changes of contract liabilities Concept (Monetary) For Period Debit cht:SignificantChangesOfContractLiabilities
1952 101690 - Disclosure - Revenue - Summary of Revenue Recognized (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureRevenueSummaryOfRevenueRecognizedDetail
1953 Implied Table Table

*

*

 implied:Table
1954 Revenue From Contract With Customer [Abstract] Abstract us-gaap:RevenueFromContractWithCustomerAbstract
1955 Telecommunications business Concept (Monetary) For Period Credit cht:RevenueFromTelecommunicationsBusiness
1956 Project business Concept (Monetary) For Period Credit cht:RevenueFromProjectBusiness
1957 Others Concept (Monetary) For Period Credit cht:RevenueFromOtherServices
1958 Contracts with customers revenue recognized Concept (Monetary) For Period Credit cht:ContractsWithCustomersRevenueRecognized
1959 101700 - Disclosure - Revenue - Summary of Incremental Costs of Obtaining Contracts (Detail) Network

*

*

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1960 Implied Table Table

*

*

 implied:Table
1961 Revenue From Contract With Customer [Abstract] Abstract us-gaap:RevenueFromContractWithCustomerAbstract
1962 Incremental costs of obtaining a contract Concept (Monetary) As Of Debit ifrs-full:AssetsRecognisedFromCostsToObtainOrFulfilContractsWithCustomers
1963 101710 - Disclosure - Revenue - Additional Information (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureRevenueAdditionalInformationDetail
1964 Revenue From Contract With Customer [Table] Table

*

*

 cht:RevenueFromContractWithCustomerTable
1965 Products and services [axis] Axis ifrs-full:ProductsAndServicesAxis
1966 Products and services [member] Member ifrs-full:ProductsAndServicesMember
1967 Telecommunications Business [Member] Member cht:TelecommunicationsBusinessMember
1968 Project Business [Member] Member cht:ProjectBusinessMember
1969 Maturity [axis] Axis ifrs-full:MaturityAxis
1970 Aggregated time bands [member] Member ifrs-full:AggregatedTimeBandsMember
1971 Not later than one year [member] Member ifrs-full:NotLaterThanOneYearMember
1972 Later than one year and not later than two years [member] Member ifrs-full:LaterThanOneYearAndNotLaterThanTwoYearsMember
1973 Later than two years and not later than three years [member] Member ifrs-full:LaterThanTwoYearsAndNotLaterThanThreeYearsMember
1974 Revenue From Contract With Customer [Abstract] Abstract us-gaap:RevenueFromContractWithCustomerAbstract
1975 Revenue From Contract With Customer Line Item Abstract cht:RevenueFromContractWithCustomerLineItem
1976 Amortisation Assets Recognised From Costs Incurred To Obtain Or Fulfil Contracts With Customers Concept (Monetary) For Period Debit ifrs-full:AmortisationAssetsRecognisedFromCostsIncurredToObtainOrFulfilContractsWithCustomers
1977 Transaction Price Allocated To Remaining Performance Obligations Concept (Monetary) As Of Credit ifrs-full:TransactionPriceAllocatedToRemainingPerformanceObligations
1978 Explanation Of When Entity Expects To Recognise Transaction Price Allocated To Remaining Performance Obligations As Revenue Concept (Text/String) For Period ifrs-full:ExplanationOfWhenEntityExpectsToRecogniseTransactionPriceAllocatedToRemainingPerformanceObligationsAsRevenue
1979 101710 - Disclosure - Revenue - Additional Information (Detail) Network

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*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureRevenueAdditionalInformationDetail
1980 Implied Table Table

*

*

 implied:Table
1981 Revenue From Contract With Customer [Abstract] Abstract us-gaap:RevenueFromContractWithCustomerAbstract
1982 Revenue From Contract With Customer Line Item Abstract cht:RevenueFromContractWithCustomerLineItem
1983 Amortization of incremental costs of obtaining contracts Concept (Monetary) For Period Debit ifrs-full:AmortisationAssetsRecognisedFromCostsIncurredToObtainOrFulfilContractsWithCustomers
1984 Transaction price allocated to performance obligations Concept (Monetary) As Of Credit ifrs-full:TransactionPriceAllocatedToRemainingPerformanceObligations
1985 Remaining performance obligations, timing of satisfaction Concept (Text/String) For Period ifrs-full:ExplanationOfWhenEntityExpectsToRecogniseTransactionPriceAllocatedToRemainingPerformanceObligationsAsRevenue
1986 101720 - Disclosure - Net Income and Other Comprehensive Income (Loss) - Other Income and Expenses (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureNetIncomeAndOtherComprehensiveIncomeLossOtherIncomeAndExpensesDetail
1987 Implied Table Table

*

*

 implied:Table
1988 Analysis Of Income And Expense [Abstract] Abstract ifrs-full:AnalysisOfIncomeAndExpenseAbstract
1989 Gain or loss on disposal of property, plant and equipment Concept (Monetary) For Period Credit ifrs-full:GainsLossesOnDisposalsOfPropertyPlantAndEquipment
1990 Reversal of impairment loss on investment properties Concept (Monetary) For Period ifrs-full:ReversalOfImpairmentLossRecognisedInProfitOrLossInvestmentProperty
1991 Loss on disposal of intangible assets Concept (Monetary) For Period Debit cht:LossOnDisposalOfIntangibleAssets
1992 Impairment loss on intangible assets Concept (Monetary) For Period ifrs-full:ImpairmentLossRecognisedInProfitOrLossIntangibleAssetsAndGoodwill
1993 Impairment loss on property, plant and equipment Concept (Monetary) For Period ifrs-full:ImpairmentLossRecognisedInProfitOrLossPropertyPlantAndEquipment
1994 Other income and expenses Concept (Monetary) For Period Credit ifrs-full:OtherOperatingIncomeExpense
1995 101730 - Disclosure - Net Income and Other Comprehensive Income (Loss) - Other Income (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureNetIncomeAndOtherComprehensiveIncomeLossOtherIncomeDetail
1996 Implied Table Table

*

*

 implied:Table
1997 Analysis Of Income And Expense [Abstract] Abstract ifrs-full:AnalysisOfIncomeAndExpenseAbstract
1998 Dividend income Concept (Monetary) For Period Credit ifrs-full:RevenueFromDividends
1999 Rental income Concept (Monetary) For Period Credit ifrs-full:RentalIncome
2000 Income from Piping Fund Concept (Monetary) For Period Credit cht:IncomeFromFund
2001 Others Concept (Monetary) For Period Credit cht:MiscellaneousOtherNonOperatingIncome
2002 Other income Concept (Monetary) For Period Credit cht:OtherNonOperatingIncome1
2003 101740 - Disclosure - Net Income and Other Comprehensive Income (Loss) - Other Gains and Losses (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureNetIncomeAndOtherComprehensiveIncomeLossOtherGainsAndLossesDetail
2004 Implied Table Table

*

*

 implied:Table
2005 Analysis Of Income And Expense [Abstract] Abstract ifrs-full:AnalysisOfIncomeAndExpenseAbstract
2006 Net foreign currency exchange gains or losses Concept (Monetary) For Period Credit ifrs-full:NetForeignExchangeGain
2007 Gain on disposal of financial instruments Concept (Monetary) For Period Credit cht:GainLossesOnDisposalOfFinancialInstruments
2008 Gain or loss on disposal of investments accounted for using equity method Concept (Monetary) For Period Credit cht:GainLossOnDisposalOfInvestmentsAccountedForUsingEquityMethodNet
2009 Valuation gain or loss on financial assets and liabilities at fair value through profit or loss, net Concept (Monetary) For Period Credit cht:GainsLossesOnFinancialAssetsAndLiabilitiesAtFairValueThroughProfitOrLoss
2010 Impairment loss on available-for-sale financial assets Concept (Monetary) For Period Debit cht:ImpairmentLossReversalOfImpairmentLossRecognisedInProfitOrLossAvailableforsaleFinancialAssets
2011 Others Concept (Monetary) For Period Credit cht:MiscellaneousOtherGainsLosses
2012 Other gains and losses Concept (Monetary) For Period Credit ifrs-full:OtherGainsLosses
2013 101750 - Disclosure - Net Income and Other Comprehensive Income (Loss) - Impairment Loss (Reversal of Impairment Loss) on Financial Instruments and Non-financial Assets (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureNetIncomeAndOtherComprehensiveIncomeLossImpairmentLossReversalOfImpairmentLossOnFinancialInstrumentsAndNonFinancialAssetsDetail
2014 Implied Table Table

*

*

 implied:Table
2015 Disclosure Of Impairment Loss And Reversal Of Impairment Loss [Abstract] Abstract ifrs-full:DisclosureOfImpairmentLossAndReversalOfImpairmentLossAbstract
2016 Contract assets Concept (Monetary) For Period Debit ifrs-full:ImpairmentLossOnReceivablesOrContractAssetsArisingFromContractsWithCustomers
2017 Trade notes and accounts receivable Concept (Monetary) For Period Debit ifrs-full:ImpairmentLossReversalOfImpairmentLossRecognisedInProfitOrLossTradeReceivables
2018 Available-for-sale financial assets Concept (Monetary) For Period Debit cht:ImpairmentLossReversalOfImpairmentLossRecognisedInProfitOrLossAvailableforsaleFinancialAssets
2019 Other receivables Concept (Monetary) For Period Debit cht:ImpairmentLossReversalOfImpairmentLossRecognisedInProfitOrLossOtherReceivables
2020 Inventories Concept (Monetary) For Period ifrs-full:InventoryWritedown2011
2021 Property, plant and equipment Concept (Monetary) For Period ifrs-full:WritedownsReversalsOfPropertyPlantAndEquipment
2022 Reversal of impairment loss on investment properties Concept (Monetary) For Period ifrs-full:ReversalOfImpairmentLossRecognisedInProfitOrLossInvestmentProperty
2023 Intangible assets Concept (Monetary) For Period ifrs-full:ImpairmentLossRecognisedInProfitOrLossIntangibleAssetsAndGoodwill
2024 101760 - Disclosure - Net Income and Other Comprehensive Income (Loss) - Depreciation and Amortization Expenses (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureNetIncomeAndOtherComprehensiveIncomeLossDepreciationAndAmortizationExpensesDetail
2025 Disclosure Of Depreciation And Amortization [Table] Table

*

*

 cht:DisclosureOfDepreciationAndAmortizationTable
2026 Statement Of Comprehensive Income Profit Or Loss Location Axis cht:StatementOfComprehensiveIncomeProfitOrLossLocationAxis
2027 Income Statement Locations Member cht:IncomeStatementLocationsDomain
2028 Operating costs [Member] Member cht:OperatingCostsMember
2029 Operating expenses [Member] Member cht:OperatingExpensesMember
2030 Marketing expenses [Member] Member cht:MarketingExpensesMember
2031 General and administrative expenses [Member] Member cht:GeneralAndAdministrativeExpensesMember
2032 Research and development expenses [Member] Member cht:ResearchAndDevelopmentExpensesMember
2033 Disclosure Of Depreciation And Amortization [Line Items] LineItems cht:DisclosureOfDepreciationAndAmortizationLineItems
2034 Property, plant and equipment Concept (Monetary) For Period ifrs-full:DepreciationPropertyPlantAndEquipment
2035 Investment properties Concept (Monetary) For Period ifrs-full:DepreciationInvestmentProperty
2036 Intangible assets Concept (Monetary) For Period ifrs-full:AmortisationIntangibleAssetsOtherThanGoodwill
2037 Amortization of incremental costs of obtaining contracts Concept (Monetary) For Period Debit ifrs-full:AmortisationAssetsRecognisedFromCostsIncurredToObtainOrFulfilContractsWithCustomers
2038 Total depreciation and amortization expenses Concept (Monetary) For Period Debit ifrs-full:DepreciationAndAmortisationExpense
2039 Depreciation expenses Concept (Monetary) For Period Debit ifrs-full:DepreciationExpense
2040 Amortization expenses Concept (Monetary) For Period Debit cht:AmortisationAndIncrementalCostsOfObtainingContracts
2041 101770 - Disclosure - Net Income and Other Comprehensive Income (Loss) - Employee Benefit Expenses (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureNetIncomeAndOtherComprehensiveIncomeLossEmployeeBenefitExpensesDetail
2042 Disclosure Of Employee Benefit Expenses [Table] Table

*

*

 cht:DisclosureOfEmployeeBenefitExpensesTable
2043 Statement Of Comprehensive Income Profit Or Loss Location Axis cht:StatementOfComprehensiveIncomeProfitOrLossLocationAxis
2044 Income Statement Locations Member cht:IncomeStatementLocationsDomain
2045 Operating costs [Member] Member cht:OperatingCostsMember
2046 Operating expenses [Member] Member cht:OperatingExpensesMember
2047 Disclosure Of Employee Benefit Expenses [Line Items] LineItems cht:DisclosureOfEmployeeBenefitExpensesLineItems
2048 Defined contribution plans Concept (Monetary) For Period Debit ifrs-full:PostemploymentBenefitExpenseDefinedContributionPlans
2049 Defined benefit plans pension costs recognized in profit and loss Concept (Monetary) For Period Debit ifrs-full:PostemploymentBenefitExpenseDefinedBenefitPlans
2050 Post-employment benefit Concept (Monetary) For Period Debit cht:PostEmploymentBenefitExpense
2051 Compensation cost of share-based payment transactions Concept (Monetary) For Period Debit ifrs-full:ExpenseFromSharebasedPaymentTransactionsWithEmployees
2052 Salaries Concept (Monetary) For Period Debit ifrs-full:WagesAndSalaries
2053 Insurance Concept (Monetary) For Period Debit ifrs-full:InsuranceExpense
2054 Others Concept (Monetary) For Period Debit ifrs-full:OtherShorttermEmployeeBenefits
2055 Other employee benefit Concept (Monetary) For Period Debit ifrs-full:ShorttermEmployeeBenefitsExpense
2056 Employee benefit expenses Concept (Monetary) For Period Debit ifrs-full:EmployeeBenefitsExpense
2057 Summary by functions Abstract cht:SummaryByFunctionsAbstract
2058 Compensation distributed to the employees Concept (Monetary) For Period Debit ifrs-full:OtherLongtermBenefits
2059 Remuneration paid to the directors Concept (Monetary) For Period Debit ifrs-full:DirectorsRemunerationExpense
2060 101780 - Disclosure - Net Income and Other Comprehensive Income (Loss) - Additional Information (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureNetIncomeAndOtherComprehensiveIncomeLossAdditionalInformationDetail
2061 Employee Benefits Expense [Table] Table

*

*

 cht:EmployeeBenefitsExpenseTable
2062 Range [axis] Axis ifrs-full:RangeAxis
2063 Ranges [member] Member ifrs-full:RangesMember
2064 Bottom of Range [Member] Member ifrs-full:BottomOfRangeMember
2065 Top of Range [Member] Member ifrs-full:TopOfRangeMember
2066 Employee benefits expense [Line Items] LineItems cht:EmployeeBenefitsExpenseLineItems
2067 Employees' compensation distribution rate Concept (Percent) For Period cht:EmployeeCompensationDistributionPercentage
2068 Directors' remuneration distribution rate Concept (Percent) For Period cht:DirectorsRemunerationDistributionPercentage
2069 Employees' compensation payables Concept (Monetary) As Of Credit cht:EmployeesCompensationPayables
2070 Remuneration to directors payables Concept (Monetary) As Of Credit cht:RemunerationToDirectorsPayables
2071 101790 - Disclosure - Net Income and Other Comprehensive Income (Loss) - Reclassification Adjustments of Other Comprehensive Income (Loss) (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureNetIncomeAndOtherComprehensiveIncomeLossReclassificationAdjustmentsOfOtherComprehensiveIncomeLossDetail
2072 Implied Table Table

*

*

 implied:Table
2073 Other Comprehensive Income [Abstract] Abstract ifrs-full:OtherComprehensiveIncomeAbstract
2074 Unrealized gain or loss on available-for-sale financial assets Abstract ifrs-full:AvailableforsaleFinancialAssetsAbstract
2075 Arising during the year Concept (Monetary) For Period Credit ifrs-full:GainsLossesOnRemeasuringAvailableforsaleFinancialAssetsBeforeTax
2076 Reclassification adjustments Abstract ifrs-full:DisclosureOfReclassificationOfFinancialAssetsAbstract
2077 Upon disposal Concept (Monetary) For Period Debit cht:ReclassificationToProfitOfLossUponDisposal
2078 Upon impairment Concept (Monetary) For Period Debit ifrs-full:ImpairmentLossRecognisedInOtherComprehensiveIncome
2079 Unrealized gain or loss on available-for- sale financial assets Concept (Monetary) For Period Credit ifrs-full:OtherComprehensiveIncomeBeforeTaxAvailableforsaleFinancialAssets
2080 Cash flow hedges Abstract ifrs-full:CashFlowHedgesAbstract
2081 Gain arising during the year Concept (Monetary) For Period Credit ifrs-full:GainsLossesOnCashFlowHedgesBeforeTax
2082 Reclassification adjustments included in profit or loss Concept (Monetary) For Period Debit ifrs-full:ReclassificationAdjustmentsOnCashFlowHedgesBeforeTax
2083 Adjusted against the carrying amount of hedged items Concept (Monetary) For Period Debit ifrs-full:AmountsRemovedFromEquityAndIncludedInCarryingAmountOfNonfinancialAssetLiabilityWhoseAcquisitionOrIncurrenceWasHedgedHighlyProbableForecastTransactionBeforeTax
2084 Cash flow hedges Concept (Monetary) For Period Credit ifrs-full:OtherComprehensiveIncomeBeforeTaxCashFlowHedges
2085 101800 - Disclosure - Income Tax - Major Components of Income Tax Expense (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureIncomeTaxMajorComponentsOfIncomeTaxExpenseDetail
2086 Implied Table Table

*

*

 implied:Table
2087 Major Components Of Tax Expense Income [Abstract] Abstract ifrs-full:MajorComponentsOfTaxExpenseIncomeAbstract
2088 Current tax Abstract ifrs-full:CurrentTaxExpenseIncomeAndAdjustmentsForCurrentTaxOfPriorPeriodsAbstract
2089 Current tax expenses recognized for the year Concept (Monetary) For Period Debit ifrs-full:CurrentTaxExpenseIncome
2090 Income tax on unappropriated earnings Concept (Monetary) For Period Debit cht:TaxEffectOfUnappropriatedEarnings
2091 Income tax adjustments on prior years Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForCurrentTaxOfPriorPeriod
2092 Others Concept (Monetary) For Period Debit cht:OtherCurrentTaxExpenseIncome
2093 Current tax Concept (Monetary) For Period Debit ifrs-full:CurrentTaxExpenseIncomeAndAdjustmentsForCurrentTaxOfPriorPeriods
2094 Deferred tax Abstract ifrs-full:DeferredTaxExpenseIncomeAbstract
2095 Deferred tax expense recognized for the year Concept (Monetary) For Period ifrs-full:DeferredTaxExpenseIncomeRecognisedInProfitOrLoss
2096 Income tax adjustments on prior years Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForDeferredTaxOfPriorPeriods
2097 Change in tax rate Concept (Monetary) For Period Debit ifrs-full:DeferredTaxExpenseIncomeRelatingToTaxRateChangesOrImpositionOfNewTaxes
2098 Deferred tax Concept (Monetary) For Period Debit ifrs-full:DeferredTaxExpenseIncome
2099 Income tax expense recognized in profit or loss Concept (Monetary) For Period Debit ifrs-full:IncomeTaxExpenseContinuingOperations
2100 101810 - Disclosure - Income Tax - Reconciliation of Accounting Profit and Income Tax Expense (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureIncomeTaxReconciliationOfAccountingProfitAndIncomeTaxExpenseDetail
2101 Implied Table Table

*

*

 implied:Table
2102 Reconciliation Of Accounting Profit Multiplied By Applicable Tax Rates [Abstract] Abstract ifrs-full:ReconciliationOfAccountingProfitMultipliedByApplicableTaxRatesAbstract
2103 Income before income tax Concept (Monetary) For Period Credit ifrs-full:ProfitLossBeforeTax
2104 Income tax expense calculated at the statutory rate (17% in 2016 and 2017, and 20% in 2018) Concept (Monetary) For Period Debit ifrs-full:TaxExpenseIncomeAtApplicableTaxRate
2105 Nondeductible income and expenses in determining taxable income Concept (Monetary) For Period Debit cht:TaxEffectOfNondeductibleRevenuesAndExpensesInDeterminingTaxableIncome
2106 Unrecognized deductible temporary differences Concept (Monetary) For Period Debit cht:TaxEffectOfUnrecognizedDeductibleTemporaryDifferences
2107 Unrecognized loss carryforwards Concept (Monetary) For Period Debit ifrs-full:TaxEffectOfTaxLosses
2108 Tax-exempt income Concept (Monetary) For Period Credit ifrs-full:TaxEffectOfRevenuesExemptFromTaxation2011
2109 Additional income tax under Alternative Minimum Tax Act Concept (Monetary) For Period Debit cht:TaxEffectOfAdditionalIncomeTaxUnderAlternativeMinimumTaxAct
2110 Income tax on unappropriated earnings Concept (Monetary) For Period Debit cht:TaxEffectOfUnappropriatedEarnings
2111 Investment credits Concept (Monetary) For Period Debit cht:TaxEffectOfTaxInvestmentCredits
2112 Change in tax rate Concept (Monetary) For Period Debit ifrs-full:TaxEffectFromChangeInTaxRate
2113 Effect of different tax rates of group entities operating in other jurisdictions Concept (Monetary) For Period Debit ifrs-full:TaxEffectOfForeignTaxRates
2114 Income tax adjustments on prior years Concept (Monetary) For Period Debit cht:TaxEffectOfTaxAdjustmentsOfTaxExpenseOnPriorYears
2115 Others Concept (Monetary) For Period Debit ifrs-full:OtherTaxEffectsForReconciliationBetweenAccountingProfitAndTaxExpenseIncome
2116 Income tax expense recognized in profit or loss Concept (Monetary) For Period Debit ifrs-full:IncomeTaxExpenseContinuingOperations
2117 101820 - Disclosure - Income Tax - Reconciliation of Accounting Profit and Income Tax Expense (Parenthetical) (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureIncomeTaxReconciliationOfAccountingProfitAndIncomeTaxExpenseParentheticalDetail
2118 Implied Table Table

*

*

 implied:Table
2119 Reconciliation Of Accounting Profit Multiplied By Applicable Tax Rates [Abstract] Abstract ifrs-full:ReconciliationOfAccountingProfitMultipliedByApplicableTaxRatesAbstract
2120 Statutory rate Concept (Percent) For Period ifrs-full:ApplicableTaxRate
2121 101830 - Disclosure - Income Tax - Additional Information (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureIncomeTaxAdditionalInformationDetail
2122 Income Tax [Table] Table

*

*

 cht:IncomeTaxTable
2123 Geographical areas [axis] Axis ifrs-full:GeographicalAreasAxis
2124 Geographical areas [member] Member ifrs-full:GeographicalAreasMember
2125 China [Member] Member country:CN
2126 Components of equity [axis] Axis ifrs-full:ComponentsOfEquityAxis
2127 Equity [member] Member ifrs-full:EquityMember
2128 Unappropriated earnings [Member] Member cht:UnappropriatedEarningsMember
2129 Income tax [Line Items] LineItems cht:IncomeTaxLineItems
2130 Applicable tax rate Concept (Percent) For Period ifrs-full:ApplicableTaxRate
2131 101840 - Disclosure - Income Tax - Income Tax Benefit Recognized in Other Comprehensive Income (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureIncomeTaxIncomeTaxBenefitRecognizedInOtherComprehensiveIncomeDetail
2132 Implied Table Table

*

*

 implied:Table
2133 Major Components Of Tax Expense Income [Abstract] Abstract ifrs-full:MajorComponentsOfTaxExpenseIncomeAbstract
2134 Deferred tax Abstract ifrs-full:IncomeTaxRelatingToComponentsOfOtherComprehensiveIncomeAbstract
2135 Remeasurement on defined benefit plan Concept (Monetary) For Period Debit ifrs-full:IncomeTaxRelatingToRemeasurementsOfDefinedBenefitPlansOfOtherComprehensiveIncome
2136 Change in tax rate Concept (Monetary) For Period Debit cht:IncomeTaxRelatingToChangeInTaxRateIncludedInOtherComprehensiveIncome
2137 Unrealized gain or loss on available-for-sale financial assets Concept (Monetary) For Period Debit ifrs-full:IncomeTaxRelatingToAvailableforsaleFinancialAssetsOfOtherComprehensiveIncome
2138 Total income tax benefit recognized in other comprehensive income Concept (Monetary) For Period ifrs-full:IncomeTaxRelatingToComponentsOfOtherComprehensiveIncome
2139 101850 - Disclosure - Income Tax - Current Tax Assets and Liabilities (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureIncomeTaxCurrentTaxAssetsAndLiabilitiesDetail
2140 Implied Table Table

*

*

 implied:Table
2141 Major Components Of Tax Expense Income [Abstract] Abstract ifrs-full:MajorComponentsOfTaxExpenseIncomeAbstract
2142 Tax refund receivable (included in other current assets - other) Concept (Monetary) As Of Debit ifrs-full:CurrentTaxAssetsCurrent
2143 Income tax payable Concept (Monetary) As Of Credit ifrs-full:CurrentTaxLiabilitiesCurrent
2144 101860 - Disclosure - Income Tax - Movements of Deferred Income Tax Assets and Liabilities (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureIncomeTaxMovementsOfDeferredIncomeTaxAssetsAndLiabilitiesDetail
2145 Income Tax [Table] Table

*

*

 cht:IncomeTaxTable
2146 Assets and liabilities [axis] Axis ifrs-full:AssetsAndLiabilitiesAxis
2147 Assets and liabilities [member] Member ifrs-full:AssetsAndLiabilitiesMember
2148 Deferred tax asset [Member] Member cht:DeferredTaxAssetMember
2149 Deferred tax liability [Member] Member cht:DeferredTaxLiabilityMember
2150 Temporary difference, unused tax losses and unused tax credits [axis] Axis ifrs-full:TemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsAxis
2151 Temporary difference, unused tax losses and unused tax credits [member] Member ifrs-full:TemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsMember
2152 Present value of funded defined benefit obligation [Member] Member ifrs-full:PresentValueOfDefinedBenefitObligationMember
2153 Allowance for doubtful accounts [Member] Member ifrs-full:AllowanceForCreditLossesMember
2154 Share of profits of associates and joint ventures accounted for using equity method [Member] Member cht:ShareOfNetProfitOfAssociatesAndJointVenturesMember
2155 Impairment loss on property, plant and equipment [Member] Member cht:ImpairmentLossOfPropertyPlantAndEquipmentMember
2156 Deferred revenue [Member] Member cht:DeferredRevenueMember
2157 Valuation loss on inventory [Member] Member cht:ValuationLossOnInventoryMember
2158 Accrued award credits liabilities [Member] Member cht:AccruedAwardCreditsLiabilitiesMember
2159 Warranties [Member] Member ifrs-full:WarrantyProvisionMember
2160 Property, plant and equipment [member] Member ifrs-full:PropertyPlantAndEquipmentMember
2161 Unrealised foreign exchange gains (losses) [Member] Member ifrs-full:UnrealisedForeignExchangeGainsLossesMember
2162 Others [Member] Member ifrs-full:OtherTemporaryDifferencesMember
2163 Temporary differences [Member] Member ifrs-full:TemporaryDifferenceMember
2164 Unused tax losses [Member] Member ifrs-full:UnusedTaxLossesMember
2165 Land value incremental tax [Member] Member cht:LandValueIncrementalTaxMember
2166 Deferred revenue for award credits [Member] Member cht:DeferredRevenueForAwardCreditsMember
2167 Intangible assets and goodwill [member] Member ifrs-full:IntangibleAssetsAndGoodwillMember
2168 Valuation gain or loss on financial instruments, net [Member] Member cht:ValuationGainOrLossOnFinancialInstrumentsNetMember
2169 Trade-in right [Member] Member cht:TradeInRightMember
2170 Income tax [Line Items] LineItems cht:IncomeTaxLineItems
2171 Beginning balance Concept (Monetary) As Of Credit ifrs-full:DeferredTaxLiabilityAsset
2172 Effect of Retrospective Applicationof IFRS 9 (Note 5) Concept (Monetary) As Of Debit ifrs-full:IncreaseDecreaseInFinancialAssetsArisingFromChangeInMeasurementAttributeFirstApplicationOfIFRS9
2173 Recognized in Profit or Loss Concept (Monetary) For Period ifrs-full:DeferredTaxExpenseIncomeRecognisedInProfitOrLoss
2174 Recognized in Other Comprehensive Income Concept (Monetary) For Period ifrs-full:IncomeTaxRelatingToComponentsOfOtherComprehensiveIncome
2175 Ending balance Concept (Monetary) As Of Credit ifrs-full:DeferredTaxLiabilityAsset
2176 Effect of Retrospective Applicationof IFRS 9(Note 5) Concept (Monetary) As Of Credit ifrs-full:IncreaseDecreaseInFinancialLiabilitiesArisingFromChangeInMeasurementAttributeFirstApplicationOfIFRS9
2177 101870 - Disclosure - Income Tax - Items for Which No Deferred Income Tax Assets Have Been Recognized (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureIncomeTaxItemsForWhichNoDeferredIncomeTaxAssetsHaveBeenRecognizedDetail
2178 Disclosure Of Temporary Difference Unused Tax Losses And Unused Tax Credits [Table] Table

*

*

 ifrs-full:DisclosureOfTemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsTable
2179 Maturity [axis] Axis ifrs-full:MaturityAxis
2180 Aggregated time bands [member] Member ifrs-full:AggregatedTimeBandsMember
2181 2019 [Member] Member cht:YearOneMember
2182 2020 [Member] Member cht:YearTwoMember
2183 2021 [Member] Member cht:YearThreeMember
2184 2022 [Member] Member cht:YearFourMember
2185 2023 [Member] Member cht:YearFiveMember
2186 2024 [Member] Member cht:YearSixMember
2187 2025 [Member] Member cht:YearSevenMember
2188 2026 [Member] Member cht:YearEightMember
2189 2027 [Member] Member cht:YearNineMember
2190 2028 [Member] Member cht:YearTenMember
2191 Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items] LineItems ifrs-full:DisclosureOfTemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsLineItems
2192 Loss carryforwards Concept (Monetary) As Of ifrs-full:UnusedTaxLossesForWhichNoDeferredTaxAssetRecognised
2193 Deductible temporary differences Concept (Monetary) As Of ifrs-full:DeductibleTemporaryDifferencesForWhichNoDeferredTaxAssetIsRecognised
2194 101880 - Disclosure - Income Tax - Information About Unused Loss Carryforwards (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureIncomeTaxInformationAboutUnusedLossCarryforwardsDetail
2195 Disclosure Of Temporary Difference Unused Tax Losses And Unused Tax Credits [Table] Table

*

*

 ifrs-full:DisclosureOfTemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsTable
2196 Temporary difference, unused tax losses and unused tax credits [axis] Axis ifrs-full:TemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsAxis
2197 Temporary difference, unused tax losses and unused tax credits [member] Member ifrs-full:TemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsMember
2198 Unused tax losses [Member] Member ifrs-full:UnusedTaxLossesMember
2199 Maturity [axis] Axis ifrs-full:MaturityAxis
2200 Aggregated time bands [member] Member ifrs-full:AggregatedTimeBandsMember
2201 2019 [Member] Member cht:YearOneMember
2202 2020 [Member] Member cht:YearTwoMember
2203 2021 [Member] Member cht:YearThreeMember
2204 2022 [Member] Member cht:YearFourMember
2205 2023 [Member] Member cht:YearFiveMember
2206 2024 [Member] Member cht:YearSixMember
2207 2025 [Member] Member cht:YearSevenMember
2208 2026 [Member] Member cht:YearEightMember
2209 2027 [Member] Member cht:YearNineMember
2210 2028 [Member] Member cht:YearTenMember
2211 Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items] LineItems ifrs-full:DisclosureOfTemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsLineItems
2212 Remaining creditable amount Concept (Monetary) As Of Debit ifrs-full:DeferredTaxAssets
2213 101890 - Disclosure - Earnings Per Share - Net Income and Weighted Average Number of Common Stocks Used in Calculation of Earnings Per Share (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureEarningsPerShareNetIncomeAndWeightedAverageNumberOfCommonStocksUsedInCalculationOfEarningsPerShareDetail
2214 Implied Table Table

*

*

 implied:Table
2215 Earnings Per Share [Abstract] Abstract ifrs-full:EarningsPerShareAbstract
2216 Net income used to compute the basic earnings per share Abstract ifrs-full:ProfitLossAttributableToOrdinaryEquityHoldersOfParentEntityAbstract
2217 Net income attributable to the parent Concept (Monetary) For Period Credit ifrs-full:ProfitLossAttributableToOwnersOfParent
2218 Assumed conversion of all dilutive potential common stocks Abstract cht:DilutiveEffectOnNetIncomeAbstract
2219 Employee stock options, employee compensation of subsidiaries Concept (Monetary) For Period Debit cht:AssumedConversionOfEmployeeStockOptionsEmployeeBonusAndCompensationOfSubsidiaries
2220 Net income used to compute the diluted earnings per share Concept (Monetary) For Period Credit ifrs-full:ProfitLossAttributableToOrdinaryEquityHoldersOfParentEntityIncludingDilutiveEffects
2221 Weighted average number of common stocks used to compute the basic earnings per share Concept (Shares) For Period ifrs-full:WeightedAverageShares
2222 Assumed conversion of all dilutive potential common stocks Abstract cht:DilutiveEffectOnNumberOfOrdinarySharesAbstract
2223 Employee compensation Concept (Shares) For Period ifrs-full:DilutiveEffectOfShareOptionsOnNumberOfOrdinaryShares
2224 Weighted average number of common stocks used to compute the diluted earnings per share Concept (Shares) For Period ifrs-full:AdjustedWeightedAverageShares
2225 101900 - Disclosure - Share-based Payment Arrangement - SENAO Share-based Compensation Plan (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureShareBasedPaymentArrangementSENAOShareBasedCompensationPlanDetail
2226 Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Table] Table

*

*

 ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementTable
2227 Subsidiaries [axis] Axis ifrs-full:SignificantInvestmentsInSubsidiariesAxis
2228 Entity's total for subsidiaries [member] Member ifrs-full:EntitysTotalForSubsidiariesMember
2229 Senao International Co., Ltd. (SENAO) [Member] Member cht:SenaoInternationalCoLtdMember
2230 Disclosure of terms and conditions of share-based payment arrangement [Line Items] LineItems ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems
2231 Effective Date Concept (Text/String) For Period cht:EffectiveDateOfGrantOfSharebasedPaymentArrangement
2232 Grant Date Concept (Text/String) For Period ifrs-full:DateOfGrantOfSharebasedPaymentArrangement
2233 Stock Options Units Concept (Decimal) For Period ifrs-full:NumberOfInstrumentsGrantedInSharebasedPaymentArrangement
2234 Exercise Price Concept (Monetary) As Of ifrs-full:ExercisePriceOfOutstandingShareOptions
2235 Original price Concept (Monetary) For Period ifrs-full:WeightedAverageSharePriceShareOptionsGranted
2236 101910 - Disclosure - Share-based Payments Arrangement - Additional Information (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureShareBasedPaymentsArrangementAdditionalInformationDetail
2237 Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Table] Table

*

*

 ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementTable
2238 Subsidiaries [axis] Axis ifrs-full:SignificantInvestmentsInSubsidiariesAxis
2239 Entity's total for subsidiaries [member] Member ifrs-full:EntitysTotalForSubsidiariesMember
2240 Senao International Co., Ltd. (SENAO) [Member] Member cht:SenaoInternationalCoLtdMember
2241 CHIEF Telecom Inc. (CHIEF) [Member] Member cht:CHIEFTelecomIncMember
2242 Chunghwa Precision Test Tech. Co., Ltd. (CHPT) [Member] Member cht:ChunghwaPrecisionTestTechCoLtdMember
2243 Types of share-based payment arrangements [axis] Axis ifrs-full:TypesOfSharebasedPaymentArrangementsAxis
2244 Share-based payment arrangements [member] Member ifrs-full:SharebasedPaymentArrangementsMember
2245 2 years after grant date [Member] Member cht:SharebasedPaymentArrangementTrancheOneMember
2246 3 years after grant date [Member] Member cht:SharebasedPaymentArrangementTrancheTwoMember
2247 4 years after grant date [Member] Member cht:SharebasedPaymentArrangementTrancheThreeMember
2248 Grant Date Axis cht:GrantDateAxis
2249 Grant Date Member Member cht:GrantDateMember
2250 Stock Option Granted in May and November 2017 [Member] Member cht:StockOptionGrantedInMayAndNovemberMember
2251 Stock Option Granted in April Member 2018 [Member] Member cht:StockOptionGrantedInAprilMember
2252 Granted on October 22, 2015 [Member] Member cht:TwentyTwoOctoberTwoThousandFifteenMember
2253 Granted on December 19, 2017 [Member] Member cht:NineteenDecemberTwoThousandSeventeenMember
2254 Granted on October 31, 2018 [Member] Member cht:ThirtyOneOctoberTwoThousandEighteenMember
2255 Disclosure of terms and conditions of share-based payment arrangement [Line Items] LineItems ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems
2256 Number of common share each option is eligible Concept (Shares) For Period cht:NumberOfSharesEntitledToAcquirePerStockOption
2257 Option expire period Concept (Text/String) For Period ifrs-full:DescriptionOfMaximumTermOfOptionsGrantedForSharebasedPaymentArrangement
2258 Vesting period Concept (Text/String) For Period ifrs-full:DescriptionOfVestingRequirementsForSharebasedPaymentArrangement
2259 Vesting percentage Concept (Percent) For Period cht:OptionsGrantedVestingPercentage
2260 Compensation costs Concept (Monetary) For Period Debit ifrs-full:ExpenseFromSharebasedPaymentTransactionsWithEmployees
2261 Exercise Price Concept (Monetary) As Of ifrs-full:ExercisePriceOfOutstandingShareOptions
2262 Number of treasury stock transfer to its specific employees Concept (Shares) For Period cht:NumberOfTreasuryStockTransferToSpecificEmployees
2263 Shares issued Concept (Shares) For Period ifrs-full:IncreaseDecreaseInNumberOfOrdinarySharesIssued
2264 Reserve for employee subscription Concept (Shares) As Of cht:ReserveForEmployeeSubscription
2265 101920 - Disclosure - Share-based Payments Arrangement - SENAO's Outstanding Stock Options (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureShareBasedPaymentsArrangementSENAOSOutstandingStockOptionsDetail
2266 Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Table] Table

*

*

 ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementTable
2267 Subsidiaries [axis] Axis ifrs-full:SignificantInvestmentsInSubsidiariesAxis
2268 Entity's total for subsidiaries [member] Member ifrs-full:EntitysTotalForSubsidiariesMember
2269 Senao International Co., Ltd. (SENAO) [Member] Member cht:SenaoInternationalCoLtdMember
2270 Disclosure of terms and conditions of share-based payment arrangement [Line Items] LineItems ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems
2271 Number of options, Options outstanding at beginning of the year Concept (Decimal) As Of ifrs-full:NumberOfOutstandingShareOptions
2272 Number of options, Options exercised Concept (Decimal) For Period ifrs-full:NumberOfShareOptionsExercisedInSharebasedPaymentArrangement
2273 Number of options, Options forfeited Concept (Decimal) For Period ifrs-full:NumberOfShareOptionsForfeitedInSharebasedPaymentArrangement
2274 Number of options, Options outstanding at end of the year Concept (Decimal) As Of ifrs-full:NumberOfOutstandingShareOptions
2275 Number of options, Options exercisable at end of the year Concept (Decimal) As Of ifrs-full:NumberOfShareOptionsExercisableInSharebasedPaymentArrangement
2276 Weighted-average exercise price, Options outstanding at beginning of the year Concept (Monetary) As Of ifrs-full:WeightedAverageExercisePriceOfShareOptionsOutstandingInSharebasedPaymentArrangement
2277 Weighted-average exercise price, Options outstanding at end of the year Concept (Monetary) As Of ifrs-full:WeightedAverageExercisePriceOfShareOptionsOutstandingInSharebasedPaymentArrangement
2278 Weighted-average exercise price, Options exercisable at end of the year Concept (Monetary) As Of ifrs-full:WeightedAverageExercisePriceOfShareOptionsExercisableInSharebasedPaymentArrangement
2279 101930 - Disclosure - Share-based Payments Arrangement - SENAO's Employee Stock Options Outstanding (Detail) Network

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*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureShareBasedPaymentsArrangementSENAOSEmployeeStockOptionsOutstandingDetail
2280 Disclosure Of Range Of Exercise Prices Of Outstanding Share Options [Table] Table

*

*

 ifrs-full:DisclosureOfRangeOfExercisePricesOfOutstandingShareOptionsTable
2281 Subsidiaries [axis] Axis ifrs-full:SignificantInvestmentsInSubsidiariesAxis
2282 Entity's total for subsidiaries [member] Member ifrs-full:EntitysTotalForSubsidiariesMember
2283 Senao International Co., Ltd. (SENAO) [Member] Member cht:SenaoInternationalCoLtdMember
2284 Disclosure of range of exercise prices of outstanding share options [Line Items] LineItems ifrs-full:DisclosureOfRangeOfExercisePricesOfOutstandingShareOptionsLineItems
2285 Range of Exercise Price Concept (Monetary) As Of ifrs-full:ExercisePriceOfOutstandingShareOptions
2286 Number of Options Outstanding Concept (Decimal) As Of ifrs-full:NumberOfOutstandingShareOptions
2287 Weighted-average Remaining Contractual Life (Years) Concept (Decimal) As Of ifrs-full:WeightedAverageRemainingContractualLifeOfOutstandingShareOptions
2288 Weighted-average Exercise Price Concept (Monetary) As Of ifrs-full:WeightedAverageExercisePriceOfShareOptionsOutstandingInSharebasedPaymentArrangement
2289 Options Exercisable Number of Options Concept (Decimal) As Of ifrs-full:NumberOfShareOptionsExercisableInSharebasedPaymentArrangement
2290 Option Exercisable Weighted-average Exercise Price Concept (Monetary) As Of ifrs-full:WeightedAverageExercisePriceOfShareOptionsExercisableInSharebasedPaymentArrangement
2291 101940 - Disclosure - Share-based Payments Arrangement - Black-Scholes Model and Related Assumptions used to Evaluate Options and Fair Value of Options by SENAO (Detail) Network

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*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureShareBasedPaymentsArrangementBlackScholesModelAndRelatedAssumptionsUsedToEvaluateOptionsAndFairValueOfOptionsBySENAODetail
2292 Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Table] Table

*

*

 ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementTable
2293 Subsidiaries [axis] Axis ifrs-full:SignificantInvestmentsInSubsidiariesAxis
2294 Entity's total for subsidiaries [member] Member ifrs-full:EntitysTotalForSubsidiariesMember
2295 Senao International Co., Ltd. (SENAO) [Member] Member cht:SenaoInternationalCoLtdMember
2296 Disclosure of terms and conditions of share-based payment arrangement [Line Items] LineItems ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems
2297 Grant-date share price Concept (Share) For Period cht:SharePricePerShare
2298 Exercise price Concept (Monetary) For Period ifrs-full:ExercisePriceShareOptionsGranted
2299 Dividends yield Concept (Percent) For Period ifrs-full:ExpectedDividendAsPercentageShareOptionsGranted
2300 Risk-free interest rate Concept (Percent) For Period ifrs-full:DescriptionOfRiskFreeInterestRateShareOptionsGranted
2301 Expected life Concept (Decimal) For Period ifrs-full:DescriptionOfOptionLifeShareOptionsGranted
2302 Expected volatility Concept (Percent) For Period ifrs-full:DescriptionOfExpectedVolatilityShareOptionsGranted
2303 Weighted-average fair value of grants Concept (Monetary) As Of Credit ifrs-full:WeightedAverageFairValueAtMeasurementDateShareOptionsGranted
2304 101950 - Disclosure - Share-based Payments Arrangement - CHIEF Share-based Compensation Plan (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureShareBasedPaymentsArrangementCHIEFShareBasedCompensationPlanDetail
2305 Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Table] Table

*

*

 ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementTable
2306 Subsidiaries [axis] Axis ifrs-full:SignificantInvestmentsInSubsidiariesAxis
2307 Entity's total for subsidiaries [member] Member ifrs-full:EntitysTotalForSubsidiariesMember
2308 CHIEF Telecom Inc. (CHIEF) [Member] Member cht:CHIEFTelecomIncMember
2309 Grant Date Axis cht:GrantDateAxis
2310 Grant Date Member Member cht:GrantDateMember
2311 Grant Date 2015.10.22 [Member] Member cht:TwentyTwoOctoberTwoThousandFifteenMember
2312 Grant Date 2017.12.19 [Member] Member cht:NineteenDecemberTwoThousandSeventeenMember
2313 Granted Date 2018.10.31 [Member] Member cht:ThirtyOneOctoberTwoThousandEighteenMember
2314 Disclosure of terms and conditions of share-based payment arrangement [Line Items] LineItems ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems
2315 Effective Date Concept (Text/String) For Period cht:EffectiveDateOfGrantOfSharebasedPaymentArrangement
2316 Grant Date Concept (Text/String) For Period ifrs-full:DateOfGrantOfSharebasedPaymentArrangement
2317 Stock Options Units Concept (Decimal) For Period ifrs-full:NumberOfInstrumentsGrantedInSharebasedPaymentArrangement
2318 Exercise Price Concept (Monetary) As Of ifrs-full:ExercisePriceOfOutstandingShareOptions
2319 Original price Concept (Monetary) For Period ifrs-full:WeightedAverageSharePriceShareOptionsGranted
2320 101960 - Disclosure - Share-based Payments Arrangement - CHIEF's Outstanding Stock Options (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureShareBasedPaymentsArrangementCHIEFSOutstandingStockOptionsDetail
2321 Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Table] Table

*

*

 ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementTable
2322 Subsidiaries [axis] Axis ifrs-full:SignificantInvestmentsInSubsidiariesAxis
2323 Entity's total for subsidiaries [member] Member ifrs-full:EntitysTotalForSubsidiariesMember
2324 CHIEF Telecom Inc. (CHIEF) [Member] Member cht:CHIEFTelecomIncMember
2325 Grant Date Axis cht:GrantDateAxis
2326 Grant Date Member Member cht:GrantDateMember
2327 Granted on October 22, 2015 [Member] Member cht:TwentyTwoOctoberTwoThousandFifteenMember
2328 Granted on December 19, 2017 [Member] Member cht:NineteenDecemberTwoThousandSeventeenMember
2329 Granted on October 31, 2018 [Member] Member cht:ThirtyOneOctoberTwoThousandEighteenMember
2330 Disclosure of terms and conditions of share-based payment arrangement [Line Items] LineItems ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems
2331 Number of options, Options outstanding at beginning of the year Concept (Decimal) As Of ifrs-full:NumberOfOutstandingShareOptions
2332 Number of options, Options granted Concept (Decimal) For Period ifrs-full:NumberOfShareOptionsGrantedInSharebasedPaymentArrangement
2333 Number of options, Options forfeited Concept (Decimal) For Period ifrs-full:NumberOfShareOptionsForfeitedInSharebasedPaymentArrangement
2334 Number of options, Options outstanding at end of the year Concept (Decimal) As Of ifrs-full:NumberOfOutstandingShareOptions
2335 Number of options, Options exercisable at end of the year Concept (Decimal) As Of ifrs-full:NumberOfShareOptionsExercisableInSharebasedPaymentArrangement
2336 Weighted-average exercise price, Options outstanding at beginning of the year Concept (Monetary) As Of ifrs-full:WeightedAverageExercisePriceOfShareOptionsOutstandingInSharebasedPaymentArrangement
2337 Weighted average exercise price, Options granted Concept (Monetary) For Period ifrs-full:WeightedAverageExercisePriceOfShareOptionsGrantedInSharebasedPaymentArrangement
2338 Weighted average exercise price, Options forfeited Concept (Monetary) For Period ifrs-full:WeightedAverageExercisePriceOfShareOptionsForfeitedInSharebasedPaymentArrangement
2339 Weighted-average exercise price, Options outstanding at end of the year Concept (Monetary) As Of ifrs-full:WeightedAverageExercisePriceOfShareOptionsOutstandingInSharebasedPaymentArrangement
2340 Weighted average exercise price, Option exercisable at end of the year Concept (Monetary) As Of ifrs-full:WeightedAverageExercisePriceOfShareOptionsExercisableInSharebasedPaymentArrangement
2341 Number of options, Options excercised Concept (Decimal) For Period ifrs-full:NumberOfShareOptionsExercisedInSharebasedPaymentArrangement
2342 Weighted average exercise price, Options exercised Concept (Monetary) For Period ifrs-full:WeightedAverageExercisePriceOfShareOptionsExercisedInSharebasedPaymentArrangement
2343 101970 - Disclosure - Share-based Payments Arrangement - CHIEF's Employee Stock Options Outstanding (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureShareBasedPaymentsArrangementCHIEFSEmployeeStockOptionsOutstandingDetail
2344 Disclosure Of Range Of Exercise Prices Of Outstanding Share Options [Table] Table

*

*

 ifrs-full:DisclosureOfRangeOfExercisePricesOfOutstandingShareOptionsTable
2345 Subsidiaries [axis] Axis ifrs-full:SignificantInvestmentsInSubsidiariesAxis
2346 Entity's total for subsidiaries [member] Member ifrs-full:EntitysTotalForSubsidiariesMember
2347 CHIEF Telecom Inc. (CHIEF) [Member] Member cht:CHIEFTelecomIncMember
2348 Grant Date Axis cht:GrantDateAxis
2349 Grant Date Member Member cht:GrantDateMember
2350 Granted on October 22, 2015 [Member] Member cht:TwentyTwoOctoberTwoThousandFifteenMember
2351 Granted on December 19, 2017 [Member] Member cht:NineteenDecemberTwoThousandSeventeenMember
2352 Granted on October 31, 2018 [Member] Member cht:ThirtyOneOctoberTwoThousandEighteenMember
2353 Disclosure of range of exercise prices of outstanding share options [Line Items] LineItems ifrs-full:DisclosureOfRangeOfExercisePricesOfOutstandingShareOptionsLineItems
2354 Range of Exercise Price Concept (Monetary) As Of ifrs-full:ExercisePriceOfOutstandingShareOptions
2355 Number of Options Outstanding Concept (Decimal) As Of ifrs-full:NumberOfOutstandingShareOptions
2356 Weighted-average Remaining Contractual Life (Years) Concept (Decimal) As Of ifrs-full:WeightedAverageRemainingContractualLifeOfOutstandingShareOptions
2357 Weighted-average Exercise Price Concept (Monetary) As Of ifrs-full:WeightedAverageExercisePriceOfShareOptionsOutstandingInSharebasedPaymentArrangement
2358 Options Exercisable Number of Options Concept (Decimal) As Of ifrs-full:NumberOfShareOptionsExercisableInSharebasedPaymentArrangement
2359 Option Exercisable Weighted-average Exercise Price Concept (Monetary) As Of ifrs-full:WeightedAverageExercisePriceOfShareOptionsExercisableInSharebasedPaymentArrangement
2360 101980 - Disclosure - Share-based Payments Arrangement - Black-Scholes Model and Binomial Option Pricing Model and Related Assumptions used to Evaluate Options and Fair Value of Options by CHIEF (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureShareBasedPaymentsArrangementBlackScholesModelAndBinomialOptionPricingModelAndRelatedAssumptionsUsedToEvaluateOptionsAndFairValueOfOptionsByCHIEFDetail
2361 Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Table] Table

*

*

 ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementTable
2362 Subsidiaries [axis] Axis ifrs-full:SignificantInvestmentsInSubsidiariesAxis
2363 Entity's total for subsidiaries [member] Member ifrs-full:EntitysTotalForSubsidiariesMember
2364 CHIEF Telecom Inc. (CHIEF) [Member] Member cht:CHIEFTelecomIncMember
2365 Disclosure of terms and conditions of share-based payment arrangement [Line Items] LineItems ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems
2366 Grant-date share price Concept (Share) For Period cht:SharePricePerShare
2367 Exercise price Concept (Monetary) For Period ifrs-full:ExercisePriceShareOptionsGranted
2368 Dividends yield Concept (Percent) For Period ifrs-full:ExpectedDividendAsPercentageShareOptionsGranted
2369 Risk-free interest rate Concept (Percent) For Period ifrs-full:DescriptionOfRiskFreeInterestRateShareOptionsGranted
2370 Expected life Concept (Decimal) For Period ifrs-full:DescriptionOfOptionLifeShareOptionsGranted
2371 Expected volatility Concept (Percent) For Period ifrs-full:DescriptionOfExpectedVolatilityShareOptionsGranted
2372 Weighted average fair value of grants Concept (Monetary) As Of Credit ifrs-full:WeightedAverageFairValueAtMeasurementDateShareOptionsGranted
2373 101990 - Disclosure - Share-based Payments Arrangement - Black-Scholes Model and Related Assumptions used to Evaluate Options and Fair Value of Options by CHPT (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureShareBasedPaymentsArrangementBlackScholesModelAndRelatedAssumptionsUsedToEvaluateOptionsAndFairValueOfOptionsByCHPTDetail
2374 Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Table] Table

*

*

 ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementTable
2375 Subsidiaries [axis] Axis ifrs-full:SignificantInvestmentsInSubsidiariesAxis
2376 Entity's total for subsidiaries [member] Member ifrs-full:EntitysTotalForSubsidiariesMember
2377 CHIEF Telecom Inc. (CHIEF) [Member] Member cht:CHIEFTelecomIncMember
2378 Chunghwa Precision Test Tech. Co., Ltd. (CHPT) [Member] Member cht:ChunghwaPrecisionTestTechCoLtdMember
2379 Disclosure of terms and conditions of share-based payment arrangement [Line Items] LineItems ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems
2380 Grant-date share price Concept (Share) For Period cht:SharePricePerShare
2381 Exercise price Concept (Monetary) For Period ifrs-full:ExercisePriceShareOptionsGranted
2382 Dividends yield Concept (Percent) For Period ifrs-full:ExpectedDividendAsPercentageShareOptionsGranted
2383 Risk-free interest rate Concept (Percent) For Period ifrs-full:DescriptionOfRiskFreeInterestRateShareOptionsGranted
2384 Expected life Concept (Decimal) For Period ifrs-full:DescriptionOfOptionLifeShareOptionsGranted
2385 Expected volatility Concept (Percent) For Period ifrs-full:DescriptionOfExpectedVolatilityShareOptionsGranted
2386 Weighted average fair value of grants Concept (Monetary) As Of Credit ifrs-full:WeightedAverageFairValueAtMeasurementDateShareOptionsGranted
2387 102000 - Disclosure - Non-Cash Transactions - Non-cash Investing Activities (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureNonCashTransactionsNonCashInvestingActivitiesDetail
2388 Implied Table Table

*

*

 implied:Table
2389 Noncash Investing Activities [Abstract] Abstract cht:NoncashInvestingActivitiesAbstract
2390 Increase in property, plant and equipment Concept (Monetary) For Period Debit ifrs-full:AdditionsOtherThanThroughBusinessCombinationsPropertyPlantAndEquipment
2391 Other payables Concept (Monetary) For Period Debit cht:NoncashTransactionsOtherPayables
2392 Non-cash investing activities Concept (Monetary) For Period Debit cht:NoncashInvestingActivities
2393 102010 - Disclosure - Operating Lease Arrangements - Future Aggregate Minimum Lease Payments Under Non-cancellable Operating Leases (Detail) Network

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*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureOperatingLeaseArrangementsFutureAggregateMinimumLeasePaymentsUnderNonCancellableOperatingLeasesDetail
2394 Disclosure Of Finance Lease And Operating Lease By Lessee [Table] Table

*

*

 ifrs-full:DisclosureOfFinanceLeaseAndOperatingLeaseByLesseeTable
2395 Maturity [axis] Axis ifrs-full:MaturityAxis
2396 Aggregated time bands [member] Member ifrs-full:AggregatedTimeBandsMember
2397 Within one year [Member] Member ifrs-full:NotLaterThanOneYearMember
2398 1-5 Years [Member] Member ifrs-full:LaterThanOneYearAndNotLaterThanFiveYearsMember
2399 More Than 5 Year [Member] Member ifrs-full:LaterThanFiveYearsMember
2400 Disclosure of finance lease and operating lease by lessee [Line Items] LineItems ifrs-full:DisclosureOfFinanceLeaseAndOperatingLeaseByLesseeLineItems
2401 Minimum lease payments under non-cancellable operating leases Concept (Monetary) As Of Credit ifrs-full:MinimumLeasePaymentsPayableUnderNoncancellableOperatingLease
2402 102020 - Disclosure - Operating Lease Arrangements - Future Aggregate Minimum Lease Collection Under Non-cancellable Operating Leases (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureOperatingLeaseArrangementsFutureAggregateMinimumLeaseCollectionUnderNonCancellableOperatingLeasesDetail
2403 Disclosure Of Finance Lease And Operating Lease By Lessor [Table] Table

*

*

 ifrs-full:DisclosureOfFinanceLeaseAndOperatingLeaseByLessorTable
2404 Maturity [axis] Axis ifrs-full:MaturityAxis
2405 Aggregated time bands [member] Member ifrs-full:AggregatedTimeBandsMember
2406 Within one year [Member] Member ifrs-full:NotLaterThanOneYearMember
2407 1-5 Years [Member] Member ifrs-full:LaterThanOneYearAndNotLaterThanFiveYearsMember
2408 More Than 5 Year [Member] Member ifrs-full:LaterThanFiveYearsMember
2409 Disclosure of finance lease and operating lease by lessor [Line Items] LineItems ifrs-full:DisclosureOfFinanceLeaseAndOperatingLeaseByLessorLineItems
2410 Minimum lease collection under non-cancellable operating leases Concept (Monetary) As Of Debit ifrs-full:MinimumLeasePaymentsReceivableUnderNoncancellableOperatingLease
2411 102030 - Disclosure - Financial Instruments - Categories of Financial Instruments (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureFinancialInstrumentsCategoriesOfFinancialInstrumentsDetail
2412 Disclosure Of Financial Instruments [Table] Table

*

*

 ifrs-full:DisclosureOfFinancialInstrumentsTable
2413 Types of hedges [axis] Axis ifrs-full:TypesOfHedgesAxis
2414 Hedges [member] Member ifrs-full:TypesOfHedgesMember
2415 Cash flow hedges [member] Member ifrs-full:CashFlowHedgesMember
2416 Disclosure of detailed information about financial instruments [Line Items] LineItems ifrs-full:DisclosureOfFinancialInstrumentsLineItems
2417 Financial assets Abstract ifrs-full:CategoriesOfFinancialAssetsAbstract
2418 Financial assets measured at FVTPL Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAtFairValueThroughProfitOrLossMandatorilyMeasuredAtFairValue
2419 Hedging financial assets Concept (Monetary) As Of Debit ifrs-full:HedgingInstrumentAssets
2420 Loans and receivables (Note a) Concept (Monetary) As Of Debit ifrs-full:LoansAndReceivables
2421 Available-for-sale financial assets Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAvailableforsale
2422 Financial assets at amortized cost (Note a) Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAtAmortisedCost
2423 Financial assets at FVOCI Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAtFairValueThroughOtherComprehensiveIncome
2424 Financial liabilities Abstract ifrs-full:CategoriesOfFinancialLiabilitiesAbstract
2425 Measured at FVTPL Held for trading Concept (Monetary) As Of Credit ifrs-full:FinancialLiabilitiesAtFairValueThroughProfitOrLossClassifiedAsHeldForTrading
2426 Hedging derivative financial liabilities Concept (Monetary) As Of Credit ifrs-full:DerivativeFinancialLiabilities
2427 Measured at amortized cost (Note b) Concept (Monetary) As Of Credit ifrs-full:FinancialLiabilitiesAtAmortisedCost
2428 102040 - Disclosure - Financial Instruments - Assets and Liabilities related to Foreign Currency Risk (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureFinancialInstrumentsAssetsAndLiabilitiesRelatedToForeignCurrencyRiskDetail
2429 Disclosure Of Financial Instruments [Table] Table

*

*

 ifrs-full:DisclosureOfFinancialInstrumentsTable
2430 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
2431 Risks [member] Member ifrs-full:TypesOfRisksMember
2432 Foreign currency risk [Member] Member ifrs-full:CurrencyRiskMember
2433 Currency Axis srt:CurrencyAxis
2434 All Currencies Member currency:AllCurrenciesDomain
2435 USD [Member] Member currency:USD
2436 EUR [Member] Member currency:EUR
2437 SGD [Member] Member currency:SGD
2438 RMB [Member] Member currency:CNY
2439 JPY [Member] Member currency:JPY
2440 Disclosure of detailed information about financial instruments [Line Items] LineItems ifrs-full:DisclosureOfFinancialInstrumentsLineItems
2441 Foreign currency denominated monetary assets Concept (Monetary) As Of Debit ifrs-full:FinancialAssets
2442 Foreign currency denominated monetary liabilities Concept (Monetary) As Of Credit ifrs-full:FinancialLiabilities
2443 Derivatives assets Concept (Monetary) As Of Debit ifrs-full:DerivativeFinancialAssets
2444 Derivatives liabilities Concept (Monetary) As Of Credit ifrs-full:DerivativeFinancialLiabilities
2445 102050 - Disclosure - Financial Instruments - Additional Information (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureFinancialInstrumentsAdditionalInformationDetail
2446 Disclosure Of Financial Instruments [Table] Table

*

*

 ifrs-full:DisclosureOfFinancialInstrumentsTable
2447 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
2448 Risks [member] Member ifrs-full:TypesOfRisksMember
2449 Foreign currency risk [Member] Member ifrs-full:CurrencyRiskMember
2450 Interest rate risk [member] Member ifrs-full:InterestRateRiskMember
2451 Equity price risk [Member] Member ifrs-full:EquityPriceRiskMember
2452 Disclosure of detailed information about financial instruments [Line Items] LineItems ifrs-full:DisclosureOfFinancialInstrumentsLineItems
2453 Sensitivity rate Concept (Percent) As Of cht:RiskExposureAssociatedWithInstrumentsSharingCharacteristicPercentageChangeInRisk
2454 Increase decrease in pre-tax income due to sensitivity analysis Concept (Monetary) As Of ifrs-full:RiskExposureAssociatedWithInstrumentsSharingCharacteristic
2455 Increase decrease in pretax income of financial assets at FVTPL Concept (Monetary) As Of cht:OtherComprehensiveIncomeIncreaseDecreaseInPretaxIncomeOfFinancialAssetsAtFairValueThroughProfitOrLoss
2456 Increase decrease in pretax income of financial assets at FVTOCI Concept (Monetary) As Of cht:OtherComprehensiveIncomeIncreaseDecreaseInPretaxIncomeOfFinancialAssetsAtFairValueThroughOtherComprehensiveIncome
2457 Increase decrease in pre-tax income due to sensitivity analysis Concept (Monetary) As Of cht:OtherComprehensiveIncomeIncreaseDecreaseInPretaxIncomeDueToSensitivityAnalysis
2458 102060 - Disclosure - Financial Instruments - Foreign Currency Risk Sensitivity Analysis (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureFinancialInstrumentsForeignCurrencyRiskSensitivityAnalysisDetail
2459 Disclosure Of Financial Instruments [Table] Table

*

*

 ifrs-full:DisclosureOfFinancialInstrumentsTable
2460 Sensitivity Analysis Axis cht:SensitivityAnalysisAxis
2461 Sensitivity Analysis Member cht:SensitivityAnalysisDomain
2462 Profit and loss [Member] Member cht:ProfitAndLossMember
2463 Equity [member] Member ifrs-full:EquityMember
2464 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
2465 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
2466 Financial instruments [Member] Member cht:FinancialInstrumentsMember
2467 Derivatives [Member] Member ifrs-full:DerivativesMember
2468 Currency Axis srt:CurrencyAxis
2469 All Currencies Member currency:AllCurrenciesDomain
2470 USD [Member] Member currency:USD
2471 EUR [Member] Member currency:EUR
2472 SGD [Member] Member currency:SGD
2473 RMB [Member] Member currency:CNY
2474 JPY [Member] Member currency:JPY
2475 Disclosure of detailed information about financial instruments [Line Items] LineItems ifrs-full:DisclosureOfFinancialInstrumentsLineItems
2476 Sensitivity analysis due to a 5% increase or decrease in foreign currency exchange Concept (Monetary) As Of cht:ChangeInProfitOrLossDueToRiskExposureArisesFromPossibleChangesInForeignExchangeRates
2477 Sensitivity analysis due to a 5% increase or decrease in foreign currency exchange Concept (Monetary) As Of cht:ChangeInEquityDueToRiskExposureArisesFromPossibleChangesInForeignExchangeRates
2478 102070 - Disclosure - Financial Instruments - Remaining Contractual Maturity for Non-derivative Financial Liabilities (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureFinancialInstrumentsRemainingContractualMaturityForNonDerivativeFinancialLiabilitiesDetail
2479 Disclosure Of Maturity Analysis For Nonderivative Financial Liabilities [Table] Table

*

*

 ifrs-full:DisclosureOfMaturityAnalysisForNonderivativeFinancialLiabilitiesTable
2480 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
2481 Risks [member] Member ifrs-full:TypesOfRisksMember
2482 Fair value interest rate risk [Member] Member cht:FairValueInterestRateRiskMember
2483 Cash flow interest rate risk [Member] Member cht:CashFlowInterestRateRiskMember
2484 Types of interest rates [axis] Axis ifrs-full:TypesOfInterestRatesAxis
2485 Interest rate types [member] Member ifrs-full:InterestRateTypesMember
2486 Non-interest bearing [Member] Member cht:NonInterestBearingMember
2487 Floating interest rate instruments [Member] Member ifrs-full:FloatingInterestRateMember
2488 Maturity [axis] Axis ifrs-full:MaturityAxis
2489 Aggregated time bands [member] Member ifrs-full:AggregatedTimeBandsMember
2490 Less Than 1 Month [Member] Member ifrs-full:NotLaterThanOneMonthMember
2491 1-3 Months [Member] Member ifrs-full:LaterThanOneMonthAndNotLaterThanThreeMonthsMember
2492 3 Months to 1 Year [Member] Member ifrs-full:LaterThanThreeMonthsAndNotLaterThanOneYearMember
2493 1-5 Years [Member] Member ifrs-full:LaterThanOneYearAndNotLaterThanFiveYearsMember
2494 More Than 5 Year [Member] Member ifrs-full:LaterThanFiveYearsMember
2495 Range [axis] Axis ifrs-full:RangeAxis
2496 Ranges [member] Member ifrs-full:RangesMember
2497 Weighted average [Member] Member ifrs-full:WeightedAverageMember
2498 Bottom of Range [Member] Member ifrs-full:BottomOfRangeMember
2499 Top of Range [Member] Member ifrs-full:TopOfRangeMember
2500 Disclosure of maturity analysis for non-derivative financial liabilities [Line Items] LineItems ifrs-full:DisclosureOfMaturityAnalysisForNonderivativeFinancialLiabilitiesLineItems
2501 Financial assets Concept (Monetary) As Of Debit ifrs-full:FinancialAssets
2502 Financial liabilities Concept (Monetary) As Of Credit ifrs-full:FinancialLiabilities
2503 Loans Concept (Monetary) As Of Credit ifrs-full:TradeAndOtherPayablesUndiscountedCashFlows
2504 Loans Concept (Monetary) As Of Credit ifrs-full:BankBorrowingsUndiscountedCashFlows
2505 Non-derivative financial liabilities Concept (Monetary) As Of Credit ifrs-full:NonderivativeFinancialLiabilitiesUndiscountedCashFlows
2506 Weighted Average Effective Interest Rate Concept (Percent) As Of ifrs-full:BorrowingsInterestRate
2507 102080 - Disclosure - Financial Instruments - Liquidity Analysis for Derivative Financial Instruments (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureFinancialInstrumentsLiquidityAnalysisForDerivativeFinancialInstrumentsDetail
2508 Disclosure Of Maturity Analysis For Derivative Financial Liabilities [Table] Table

*

*

 ifrs-full:DisclosureOfMaturityAnalysisForDerivativeFinancialLiabilitiesTable
2509 Maturity [axis] Axis ifrs-full:MaturityAxis
2510 Aggregated time bands [member] Member ifrs-full:AggregatedTimeBandsMember
2511 Less Than 1 Month [Member] Member ifrs-full:NotLaterThanOneMonthMember
2512 1-3 Months [Member] Member ifrs-full:LaterThanOneMonthAndNotLaterThanThreeMonthsMember
2513 3 Months to 1 Year [Member] Member ifrs-full:LaterThanThreeMonthsAndNotLaterThanOneYearMember
2514 1-5 Years [Member] Member ifrs-full:LaterThanOneYearAndNotLaterThanFiveYearsMember
2515 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
2516 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
2517 Forward exchange contracts inflows [Member] Member cht:ForwardExchangeContractsInflowsMember
2518 Forward exchange contracts outflows [Member] Member cht:ForwardExchangeContractsOutflowsMember
2519 Disclosure of maturity analysis for derivative financial liabilities [Line Items] LineItems ifrs-full:DisclosureOfMaturityAnalysisForDerivativeFinancialLiabilitiesLineItems
2520 Undiscounted gross inflows (outflows) on derivatives Concept (Monetary) As Of Debit cht:DerivativeFinancialAssetsLiabilitiesUndiscountedCashFlows
2521 102090 - Disclosure - Financial Instruments - Financing Facilities (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureFinancialInstrumentsFinancingFacilitiesDetail
2522 Disclosure Of Financial Instruments [Table] Table

*

*

 ifrs-full:DisclosureOfFinancialInstrumentsTable
2523 Classes of financial liabilities [axis] Axis ifrs-full:ClassesOfFinancialLiabilitiesAxis
2524 Financial liabilities, class [member] Member ifrs-full:FinancialLiabilitiesMember
2525 Unsecured loans [Member] Member cht:UnsecuredLoansMember
2526 Secured loans [Member] Member cht:SecuredLoansMember
2527 Disclosure of detailed information about financial instruments [Line Items] LineItems ifrs-full:DisclosureOfFinancialInstrumentsLineItems
2528 Unsecured bank loan facility, amount used Concept (Monetary) As Of Credit ifrs-full:UnsecuredBankLoansReceived
2529 Secured loans Concept (Monetary) As Of Credit ifrs-full:SecuredBankLoansReceived
2530 Bank loan facility, amount unused Concept (Monetary) As Of Credit ifrs-full:UndrawnBorrowingFacilities
2531 Unsecured bank loan facility Concept (Monetary) As Of Credit cht:UnsecuredBankLoanFacility
2532 Secured bank loan facility Concept (Monetary) As Of Credit cht:SecuredBankLoanFacility
2533 102100 - Disclosure - Fair Value Information - Financial Instruments Measured at Fair Value on a Recurring Basis (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureFairValueInformationFinancialInstrumentsMeasuredAtFairValueOnRecurringBasisDetail
2534 Disclosure Of Fair Value Measurement Of Assets And Liabilities [Table] Table

*

*

 cht:DisclosureOfFairValueMeasurementOfAssetsAndLiabilitiesTable
2535 Measurement [axis] Axis ifrs-full:MeasurementAxis
2536 Aggregated measurement [member] Member ifrs-full:AggregatedMeasurementMember
2537 Fair value on a recurring basis [Member] Member ifrs-full:RecurringFairValueMeasurementMember
2538 Levels of fair value hierarchy [axis] Axis ifrs-full:LevelsOfFairValueHierarchyAxis
2539 All levels of fair value hierarchy [member] Member ifrs-full:AllLevelsOfFairValueHierarchyMember
2540 Level 1 [Member] Member ifrs-full:Level1OfFairValueHierarchyMember
2541 Level 2 [Member] Member ifrs-full:Level2OfFairValueHierarchyMember
2542 Level 3 [Member] Member ifrs-full:Level3OfFairValueHierarchyMember
2543 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
2544 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
2545 Non-listed stocks [Member] Member cht:NonlistedStocksMember
2546 Disclosure of fair value measurement of assets and liabilities [Line Items] LineItems cht:DisclosureOfFairValueMeasurementOfAssetsAndLiabilitiesLineItems
2547 Amount invested in investment entity Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAvailableforsale
2548 Measured at FVTPL Held for trading Concept (Monetary) As Of Credit ifrs-full:FinancialLiabilitiesAtFairValueThroughProfitOrLossClassifiedAsHeldForTrading
2549 Cash flow hedge-forward exchange contracts, financial liabilities Concept (Monetary) As Of Credit ifrs-full:DerivativeFinancialLiabilities
2550 Financial assets at FVTPL Derivatives Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAtFairValueThroughProfitOrLossClassifiedAsHeldForTrading
2551 Non-listed stocks Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAtFairValueThroughProfitOrLoss
2552 Hedging financial assets Concept (Monetary) As Of Debit ifrs-full:DerivativeFinancialAssetsHeldForHedging
2553 Equity investment Concept (Monetary) As Of Debit ifrs-full:FairValueOfInvestmentsInEquityInstrumentsDesignatedAsMeasuredAtFairValueThroughOtherComprehensiveIncome
2554 102110 - Disclosure - Fair Value Information - Additional Information (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureFairValueInformationAdditionalInformationDetail
2555 Implied Table Table

*

*

 implied:Table
2556 Disclosure Of Fair Value Measurement Of Financial Instruments [Abstract] Abstract cht:DisclosureOfFairValueMeasurementOfFinancialInstrumentsAbstract
2557 Transfer between Level 1 and 2, assets Concept (Monetary) For Period ifrs-full:TransfersOutOfLevel1IntoLevel2OfFairValueHierarchyAssets
2558 Transfer between Level 2 and 1, assets Concept (Monetary) For Period ifrs-full:TransfersOutOfLevel2IntoLevel1OfFairValueHierarchyAssets
2559 Transfer between Level 1 and 2, liabilities Concept (Monetary) For Period ifrs-full:TransfersOutOfLevel1IntoLevel2OfFairValueHierarchyLiabilities
2560 Transfer between Level 2 and 1, liabilities Concept (Monetary) For Period ifrs-full:TransfersOutOfLevel2IntoLevel1OfFairValueHierarchyLiabilities
2561 102120 - Disclosure - Fair Value Information - Schedule of Reconciliations for Financial Assets (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureFairValueInformationScheduleOfReconciliationsForFinancialAssetsDetail
2562 Disclosure Of Fair Value Measurement Of Assets [Table] Table

*

*

 ifrs-full:DisclosureOfFairValueMeasurementOfAssetsTable
2563 Levels of fair value hierarchy [axis] Axis ifrs-full:LevelsOfFairValueHierarchyAxis
2564 All levels of fair value hierarchy [member] Member ifrs-full:AllLevelsOfFairValueHierarchyMember
2565 Level 3 [Member] Member ifrs-full:Level3OfFairValueHierarchyMember
2566 Categories of financial assets [axis] Axis ifrs-full:CategoriesOfFinancialAssetsAxis
2567 Financial assets, category [member] Member ifrs-full:FinancialAssetsCategoryMember
2568 Measured at Fair Value Through Profit or Loss [Member] Member ifrs-full:FinancialAssetsAtFairValueThroughProfitOrLossCategoryMember
2569 FVOCI [Member] Member ifrs-full:FinancialAssetsAtFairValueThroughOtherComprehensiveIncomeCategoryMember
2570 Disclosure Of Fair Value Measurement Of Assets [Line Items] LineItems ifrs-full:DisclosureOfFairValueMeasurementOfAssetsLineItems
2571 Foreign currency denominated monetary assets Concept (Monetary) As Of Debit ifrs-full:FinancialAssets
2572 Effect of retrospective application of IFRS 9 Concept (Monetary) As Of Debit ifrs-full:IncreaseDecreaseInFinancialAssetsArisingFromChangeInMeasurementAttributeFirstApplicationOfIFRS9
2573 Acquisition Concept (Monetary) For Period Debit cht:Acquisition
2574 Recognized in profit or loss under “Other gains and losses” Concept (Monetary) For Period Credit cht:RecognizedInProfitOrLossUnderOtherGainsAndLosses
2575 Recognized in other comprehensive income under “Unrealized gain or loss on investments in equity instruments at fair value through other comprehensive income” Concept (Monetary) For Period Credit cht:RecognizedInOtherComprehensiveIncomeUnderUnrealizedGainOrLossOnInvestmentsInEquityInstrumentsAtFairValueThroughOtherComprehensiveIncome
2576 Proceeds from return of investees Concept (Monetary) For Period Credit cht:ProceedsFromReturnOfInvestees
2577 Unrealized loss in 2018 Concept (Monetary) For Period Debit cht:UnrealizedLossInCurrentYear
2578 102130 - Disclosure - Fair Value Information - Schedule of Percentage Decrease in Discount for Lack of Marketability or Noncontrolling Interests Discount (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureFairValueInformationScheduleOfPercentageDecreaseInDiscountForLackOfMarketabilityOrNoncontrollingInterestsDiscountDetail
2579 Disclosure Of Fair Value Measurement Of Assets And Liabilities [Table] Table

*

*

 cht:DisclosureOfFairValueMeasurementOfAssetsAndLiabilitiesTable
2580 Range [axis] Axis ifrs-full:RangeAxis
2581 Ranges [member] Member ifrs-full:RangesMember
2582 Bottom of Range [Member] Member ifrs-full:BottomOfRangeMember
2583 Top of Range [Member] Member ifrs-full:TopOfRangeMember
2584 Disclosure of fair value measurement of assets and liabilities [Line Items] LineItems cht:DisclosureOfFairValueMeasurementOfAssetsAndLiabilitiesLineItems
2585 Discount for lack of marketability Concept (Percent) For Period cht:PercentageOfDiscountForLackOfMarketability
2586 Noncontrolling interests discount Concept (Percent) For Period cht:DiscountRateOfNoncontrollingInterests
2587 102140 - Disclosure - Fair Value Information - Schedule of Impact of Decrease in Discount for Lack of Marketability or Noncontrolling Interests (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureFairValueInformationScheduleOfImpactOfDecreaseInDiscountForLackOfMarketabilityOrNoncontrollingInterestsDetail
2588 Implied Table Table

*

*

 implied:Table
2589 Disclosure Of Fair Value Measurement Of Financial Instruments [Abstract] Abstract cht:DisclosureOfFairValueMeasurementOfFinancialInstrumentsAbstract
2590 Discount for lack of marketability 5% decrease Concept (Monetary) For Period Debit cht:AmountOfDiscountForLackOfMarketabilityFivePercentageDecrease
2591 Noncontrolling interests discount 5% decrease Concept (Monetary) For Period Debit cht:AmountOfNoncontrollingInterestsDiscountFivePercentageDecrease
2592 102150 - Disclosure - Related Parties Transactions - Summary of Related Parties (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureRelatedPartiesTransactionsSummaryOfRelatedPartiesDetail
2593 Disclosure Of Transactions Between Related Parties [Table] Table

*

*

 ifrs-full:DisclosureOfTransactionsBetweenRelatedPartiesTable
2594 Legal Entity Axis dei:LegalEntityAxis
2595 Entity Member dei:EntityDomain
2596 Taiwan International Standard Electronics Co., Ltd. ("TISE") [Member] Member cht:TaiwanInternationalStandardElectronicsCoLtdMember
2597 So-net Entertainment Taiwan Limited ("So-net") [Member] Member cht:SonetEntertainmentTaiwanLimitedMember
2598 KKBOX Taiwan Co., Ltd. (“KKBOXTW”) [Member] Member cht:KKBOXTaiwanCoLtdMember
2599 KingwayTek Technology Co., Ltd. ("KWT") [Member] Member cht:KingwayTekTechnologyCoLtdMember
2600 UUPON Inc [member] Member cht:UUPONIncMember
2601 Taiwan International Ports Logistics Corporation ("TIPL") [Member] Member cht:TaiwanInternationalPortsLogisticsCorporationMember
2602 Huada Digital Corporation ("HDD") [Member] Member cht:HuadaDigitalCorporationMember
2603 Chunghwa Benefit One Co., Ltd. ("CBO") [Member] Member cht:ChunghwaBenefitOneCoLtdMember
2604 International Integrated System, Inc. ("IISI") [Member] Member cht:InternationalIntegratedSystemIncMember
2605 Senao Networks, Inc. ("SNI") [Member] Member cht:SenaoNetworksIncMember
2606 HopeTech Technologies Limited [Member] Member cht:HopeTechTechnologiesLimitedMember
2607 EnGenius Tech. Co., Ltd. [Member] Member cht:EngeniusTechCoLtdMember
2608 ST-2 Satellite Ventures Pte., Ltd. ("STS") [Member] Member cht:ST2SatelliteVenturesPteLtdMember
2609 Viettel-CHT Co., Ltd. ("Viettel-CHT") [Member] Member cht:ViettelCHTCoLtdMember
2610 Click Force Co., Ltd. ("CF") [Member] Member cht:ClickForceCoLtdMember
2611 Alliance Digital Tech Co., Ltd. ("ADT") [Member] Member cht:AllianceDigitalTechCoLtdMember
2612 MeWorks LIMITED (HK) ("MeWorks") [Member] Member cht:MeWorksLIMITEDHKMember
2613 Chunghwa PChome Fund I Co., Ltd. (“CPFI”) [member] Member cht:ChunghwaPChomeFundICoLtdCPFIMember
2614 Chunghwa Telecom Foundation [Member] Member cht:ChunghwaTelecomFoundationMember
2615 Cornerstone Ventures Co., Ltd. (“CVC”) [Member] Member cht:CornerstoneVenturesCoLtdCVCMember
2616 Senao Technical and Cultural Foundation [Member] Member cht:SenaoTechnicalAndCulturalFoundationMember
2617 Sochamp Technology Co., Ltd. [Member] Member cht:SochampTechnologyCoLtdMember
2618 E-Life Mall Co., Ltd. [Member] Member cht:ELifeMallCoLtdMember
2619 Engenius Technologies Co., Ltd. [Member] Member cht:EngeniusTechnologiesCoLtdMember
2620 United Daily News Co., Ltd. [Member] Member cht:UnitedDailyNewsCoLtdMember
2621 Shenzhen Century Communication Co., Ltd. [Member] Member cht:ShenzhenCenturyCommunicationCoLtdMember
2622 Taoyuan Aerotropolis Co., Ltd. [Member] Member cht:TaoyuanAerotropolisCoLtdMember
2623 Disclosure of transactions between related parties [Line Items] LineItems ifrs-full:DisclosureOfTransactionsBetweenRelatedPartiesLineItems
2624 Relationship Concept (Text/String) For Period ifrs-full:DescriptionOfNatureOfRelatedPartyRelationship
2625 102160 - Disclosure - Related Parties Transactions - Details of Transactions Between the Company and Other Related Parties (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureRelatedPartiesTransactionsDetailsOfTransactionsBetweenCompanyAndOtherRelatedPartiesDetail
2626 Disclosure Of Transactions Between Related Parties [Table] Table

*

*

 ifrs-full:DisclosureOfTransactionsBetweenRelatedPartiesTable
2627 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
2628 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
2629 Associates [Member] Member ifrs-full:AssociatesMember
2630 Joint ventures [Member] Member ifrs-full:JointVenturesMember
2631 Others [Member] Member ifrs-full:OtherRelatedPartiesMember
2632 Disclosure of transactions between related parties [Line Items] LineItems ifrs-full:DisclosureOfTransactionsBetweenRelatedPartiesLineItems
2633 Revenues Concept (Monetary) For Period Credit ifrs-full:RevenueFromSaleOfGoodsRelatedPartyTransactions
2634 Operating Costs and Expenses Concept (Monetary) For Period Debit cht:OperatingCostsAndExpensesRelatedPartyTransactions
2635 Non-operating Income and Expenses Concept (Monetary) For Period Credit cht:NonOperatingIncomeAndExpensesRelatedPartyTransactions
2636 Receivables Concept (Monetary) As Of Debit ifrs-full:TradeAndOtherCurrentReceivablesDueFromRelatedParties
2637 Payables Concept (Monetary) As Of Credit ifrs-full:TradeAndOtherCurrentPayablesToRelatedParties
2638 Customers' deposits Concept (Monetary) As Of Credit cht:CustomersDepositsRelatedPartyTransactions
2639 Acquisition of property, plant and equipment Concept (Monetary) For Period Debit ifrs-full:PurchasesOfPropertyAndOtherAssetsRelatedPartyTransactions
2640 Prepaid rents - current Concept (Monetary) As Of Debit cht:CurrentPrepaidRentRelatedPartyTransactions
2641 Prepaid rents - noncurrent Concept (Monetary) As Of Debit cht:NoncurrentPrepaidRentRelatedPartyTransactions
2642 Prepaid rents Concept (Monetary) As Of Debit cht:PrepaidRentRelatedPartyTransactions
2643 102170 - Disclosure - Related Parties Transactions - Additional Information (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureRelatedPartiesTransactionsAdditionalInformationDetail
2644 Disclosure Of Transactions Between Related Parties [Table] Table

*

*

 ifrs-full:DisclosureOfTransactionsBetweenRelatedPartiesTable
2645 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
2646 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
2647 ST-2 Satellite Ventures Pte., Ltd. ("STS") [Member] Member cht:ST2SatelliteVenturesPteLtdMember
2648 Disclosure of transactions between related parties [Line Items] LineItems ifrs-full:DisclosureOfTransactionsBetweenRelatedPartiesLineItems
2649 Lease period Concept (xbrli:durationItemType) For Period cht:LeaseContractForPeriod
2650 Lease contract value Concept (Monetary) As Of Credit ifrs-full:LeaseLiabilities
2651 Lease contract value, prepayment amount Concept (Monetary) As Of Debit cht:PrepaidRentRelatedPartyTransactions
2652 Rental expense Concept (Monetary) For Period Debit ifrs-full:RentalExpense
2653 Rental expense, offsetting credit of the prepayment Concept (Monetary) For Period Debit cht:RentalExpenseOffsettingCreditOfPrepayments
2654 Rental expense, additional accrual Concept (Monetary) For Period Debit cht:RentalExpenseAdditionalAccrual
2655 102180 - Disclosure - Related Parties Transactions - Compensation of Directors and Other Key Management Personnel (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureRelatedPartiesTransactionsCompensationOfDirectorsAndOtherKeyManagementPersonnelDetail
2656 Implied Table Table

*

*

 implied:Table
2657 Disclosure Of Transactions Between Related Parties [Abstract] Abstract ifrs-full:DisclosureOfTransactionsBetweenRelatedPartiesAbstract
2658 Short-term employee benefits Concept (Monetary) For Period Debit ifrs-full:KeyManagementPersonnelCompensationShorttermEmployeeBenefits
2659 Post-employment benefits Concept (Monetary) For Period Debit ifrs-full:KeyManagementPersonnelCompensationPostemploymentBenefits
2660 Share-based payment Concept (Monetary) For Period Debit ifrs-full:KeyManagementPersonnelCompensationSharebasedPayment
2661 Compensation of key management personnel Concept (Monetary) For Period Debit ifrs-full:KeyManagementPersonnelCompensation
2662 102190 - Disclosure - Pledged Assets - Assets Pledged as Collaterals (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosurePledgedAssetsAssetsPledgedAsCollateralsDetail
2663 Implied Table Table

*

*

 implied:Table
2664 Subclassifications Of Assets Liabilities And Equities [Abstract] Abstract ifrs-full:SubclassificationsOfAssetsLiabilitiesAndEquitiesAbstract
2665 Property, plant and equipment Concept (Monetary) As Of Debit ifrs-full:PropertyPlantAndEquipmentPledgedAsSecurity
2666 Land held under development (included in inventories) Concept (Monetary) As Of Debit ifrs-full:InventoriesPledgedAsSecurityForLiabilities
2667 Restricted assets (included in other assets - others) Concept (Monetary) As Of Debit cht:RestrictedDepositsCollateralPledgedAsSecurityForLiabilities
2668 Assets pledged as collateral Concept (Monetary) As Of Debit ifrs-full:AssetsHeldAsCollateralPermittedToBeSoldOrRepledgedAtFairValue
2669 102200 - Disclosure - Significant Contingent Liabilities and Unrecognized Commitments - Additional Information (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureSignificantContingentLiabilitiesAndUnrecognizedCommitmentsAdditionalInformationDetail
2670 Commitments And Contingencies [Table] Table

*

*

 cht:CommitmentsAndContingenciesTable
2671 Classes of property, plant and equipment [axis] Axis ifrs-full:ClassesOfPropertyPlantAndEquipmentAxis
2672 Property, plant and equipment [member] Member ifrs-full:PropertyPlantAndEquipmentMember
2673 Land and buildings [Member] Member ifrs-full:LandAndBuildingsMember
2674 Telecommunications equipment [Member] Member ifrs-full:CommunicationAndNetworkEquipmentMember
2675 Classes of assets [axis] Axis ifrs-full:ClassesOfAssetsAxis
2676 Assets [member] Member ifrs-full:ClassesOfAssetsMember
2677 Piping Fund [Member] Member cht:PipingFundMember
2678 Non-adjusting events after reporting period [axis] Axis ifrs-full:NonadjustingEventsAfterReportingPeriodAxis
2679 Non-adjusting events after reporting period [member] Member ifrs-full:NonadjustingEventsMember
2680 Contractual Consideration Payment [Member] Member ifrs-full:EnteringIntoSignificantCommitmentsOrContingentLiabilitiesMember
2681 Commitments And Contingencies [Line Items] LineItems cht:CommitmentsAndContingenciesLineItems
2682 Commitments for acquisitions of property, plant and equipment Concept (Monetary) As Of Credit ifrs-full:ContractualCommitmentsForAcquisitionOfPropertyPlantAndEquipment
2683 Unused letters of credit Concept (Monetary) As Of Credit cht:UnusedLettersOfCredit
2684 Commitment amount Concept (Monetary) As Of Credit ifrs-full:ContractualCapitalCommitments
2685 Commitment to contribute to a Piping Fund, amount contributed Concept (Monetary) As Of Credit ifrs-full:OutstandingCommitmentsMadeByEntityRelatedPartyTransactions
2686 Commitment to contribute to a Piping Fund, remaining amount Concept (Monetary) As Of Credit cht:RemainingContractualCapitalCommitments
2687 Contractual consideration payment Concept (Monetary) For Period Debit cht:ContractualConsiderationPayment
2688 102210 - Disclosure - Significant Subsequent Events - Additional information (Detail) Network

*

*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureSignificantSubsequentEventsAdditionalInformationDetail
2689 Disclosure Of Nonadjusting Events After Reporting Period [Table] Table

*

*

 ifrs-full:DisclosureOfNonadjustingEventsAfterReportingPeriodTable
2690 Range [axis] Axis ifrs-full:RangeAxis
2691 Ranges [member] Member ifrs-full:RangesMember
2692 Top of Range [Member] Member ifrs-full:TopOfRangeMember
2693 Bottom of Range [Member] Member ifrs-full:BottomOfRangeMember
2694 Non-adjusting events after reporting period [axis] Axis ifrs-full:NonadjustingEventsAfterReportingPeriodAxis
2695 Non-adjusting events after reporting period [member] Member ifrs-full:NonadjustingEventsMember
2696 Subsequent Events [member] Member cht:SubsequentEventsMember
2697 Disclosure Of Nonadjusting Events After Reporting Period [Line Items] LineItems ifrs-full:DisclosureOfNonadjustingEventsAfterReportingPeriodLineItems
2698 Investment in common stock Concept (Monetary) As Of Debit cht:InvestmentInCommonStock
2699 Ownership interest in associates Concept (Percent) For Period ifrs-full:ProportionOfOwnershipInterestInAssociate
2700 Prepaid establishment charges Concept (Monetary) For Period Debit cht:PrepaidEstablishmentCharges
2701 102220 - Disclosure - Segment Information - Analysis by Reportable Segment of Revenue and Operating Results of Continuing Operations (Detail) Network

*

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 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureSegmentInformationAnalysisByReportableSegmentOfRevenueAndOperatingResultsOfContinuingOperationsDetail
2702 Disclosure Of Operating Segments [Table] Table

*

*

 ifrs-full:DisclosureOfOperatingSegmentsTable
2703 Segments [axis] Axis ifrs-full:SegmentsAxis
2704 Segments [member] Member ifrs-full:SegmentsMember
2705 Domestic Fixed Communications Business [Member] Member cht:DomesticFixedCommunicationsBusinessMember
2706 Mobile Communications Business [Member] Member cht:MobileCommunicationsBusinessMember
2707 Internet Business [Member] Member cht:InternetBusinessMember
2708 International Fixed Communications Business [Member] Member cht:InternationalFixedCommunicationsBusinessMember
2709 Other [Member] Member ifrs-full:AllOtherSegmentsMember
2710 Segment consolidation items [axis] Axis ifrs-full:SegmentConsolidationItemsAxis
2711 Entity's total for segment consolidation items [member] Member ifrs-full:EntitysTotalForSegmentConsolidationItemsMember
2712 From External Customers [Member] Member cht:ExternalCustomersMember
2713 Intersegment [Member] Member cht:IntersegmentMember
2714 Segment [Member] Member ifrs-full:OperatingSegmentsMember
2715 Intersegment Elimination [Member] Member ifrs-full:EliminationOfIntersegmentAmountsMember
2716 Consolidated [Member] Member ifrs-full:ConsolidatedMember
2717 Disclosure of operating segments [Line Items] LineItems ifrs-full:DisclosureOfOperatingSegmentsLineItems
2718 Revenues Concept (Monetary) For Period Credit ifrs-full:Revenue
2719 Income before income tax Concept (Monetary) For Period Credit ifrs-full:ProfitLossBeforeTax
2720 102230 - Disclosure - Segment Information - Other Segment Information (Detail) Network

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*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureSegmentInformationOtherSegmentInformationDetail
2721 Disclosure Of Operating Segments [Table] Table

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*

 ifrs-full:DisclosureOfOperatingSegmentsTable
2722 Segments [axis] Axis ifrs-full:SegmentsAxis
2723 Segments [member] Member ifrs-full:SegmentsMember
2724 Domestic Fixed Communications Business [Member] Member cht:DomesticFixedCommunicationsBusinessMember
2725 Mobile Communications Business [Member] Member cht:MobileCommunicationsBusinessMember
2726 Internet Business [Member] Member cht:InternetBusinessMember
2727 International Fixed Communications Business [Member] Member cht:InternationalFixedCommunicationsBusinessMember
2728 Other [Member] Member ifrs-full:AllOtherSegmentsMember
2729 Disclosure of operating segments [Line Items] LineItems ifrs-full:DisclosureOfOperatingSegmentsLineItems
2730 Share of the profits of associates and joint ventures accounted for using equity method Concept (Monetary) For Period Credit ifrs-full:ShareOfProfitLossOfAssociatesAndJointVenturesAccountedForUsingEquityMethod
2731 Interest income Concept (Monetary) For Period Credit ifrs-full:RevenueFromInterest
2732 Interest expenses Concept (Monetary) For Period Debit ifrs-full:InterestExpense
2733 Operating costs and expenses Concept (Monetary) For Period Debit cht:OperatingCostsAndExpenses1
2734 Depreciation and amortization Concept (Monetary) For Period Debit ifrs-full:DepreciationAndAmortisationExpense
2735 Capital expenditure Concept (Monetary) For Period Credit ifrs-full:PurchaseOfPropertyPlantAndEquipmentClassifiedAsInvestingActivities
2736 Impairment loss on property, plant and equipment Concept (Monetary) For Period ifrs-full:ImpairmentLossRecognisedInProfitOrLossPropertyPlantAndEquipment
2737 Reversal of impairment loss Concept (Monetary) For Period ifrs-full:ReversalOfImpairmentLossRecognisedInProfitOrLossInvestmentProperty
2738 102240 - Disclosure - Segment Information - Main Products and Service Revenues (Detail) Network

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*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureSegmentInformationMainProductsAndServiceRevenuesDetail
2739 Disclosure Of Products And Services [Table] Table

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*

 ifrs-full:DisclosureOfProductsAndServicesTable
2740 Products and services [axis] Axis ifrs-full:ProductsAndServicesAxis
2741 Products and services [member] Member ifrs-full:ProductsAndServicesMember
2742 Mobile services [Member] Member cht:MobileServicesMember
2743 Local telephone and domestic long distance telephone services [Member] Member cht:LocalTelephoneAndDomesticLongDistanceTelephoneServicesMember
2744 Sales of product [Member] Member cht:SalesOfProductMember
2745 Broadband access and domestic leased line services [Member] Member cht:BroadbandAccessAndDomesticLeasedLineServicesMember
2746 Data communications internet services [Member] Member cht:DataCommunicationsInternetServicesMember
2747 International network and leased telephone services [Member] Member cht:InternationalNetworkAndLeasedTelephoneServicesMember
2748 Others [Member] Member cht:OtherProductsAndServicesMember
2749 Disclosure of products and services [Line Items] LineItems ifrs-full:DisclosureOfProductsAndServicesLineItems
2750 Revenues Concept (Monetary) For Period Credit ifrs-full:Revenue
2751 102250 - Disclosure - Segment Information - Geographic Information (Detail) Network

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*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureSegmentInformationGeographicInformationDetail
2752 Disclosure Of Geographical Areas [Table] Table

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*

 ifrs-full:DisclosureOfGeographicalAreasTable
2753 Geographical areas [axis] Axis ifrs-full:GeographicalAreasAxis
2754 Geographical areas [member] Member ifrs-full:GeographicalAreasMember
2755 Taiwan, ROC [Member] Member ifrs-full:CountryOfDomicileMember
2756 Overseas [Member] Member ifrs-full:ForeignCountriesMember
2757 Disclosure of geographical areas [Line Items] LineItems ifrs-full:DisclosureOfGeographicalAreasLineItems
2758 Revenues Concept (Monetary) For Period Credit ifrs-full:Revenue
2759 102260 - Disclosure - Segment Information - Additional Information (Detail) Network

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*

 http://www.cht.com.tw/20181231/taxonomy/role/DisclosureSegmentInformationAdditionalInformationDetail
2760 Disclosure Of Operating Segments [Table] Table

*

*

 ifrs-full:DisclosureOfOperatingSegmentsTable
2761 Geographical areas [axis] Axis ifrs-full:GeographicalAreasAxis
2762 Geographical areas [member] Member ifrs-full:GeographicalAreasMember
2763 Overseas [Member] Member ifrs-full:ForeignCountriesMember
2764 Disclosure of operating segments [Line Items] LineItems ifrs-full:DisclosureOfOperatingSegmentsLineItems
2765 Long-lived assets Concept (Monetary) As Of Debit ifrs-full:NoncurrentAssets
2766 Information about major customers Concept (Text/String) For Period ifrs-full:InformationAboutMajorCustomers

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