3.26.1 html 2038 845 1 false 564 0 false 21 false false R1.htm 0000001 - Document - Cover Page Sheet http://www.kt.com/role/CoverPage Cover Page Cover 1 false false R2.htm 0000002 - Document - Audit Information Sheet http://www.kt.com/role/AuditInformation Audit Information Cover 2 false false R3.htm 9952151 - Statement - Consolidated Statements of Financial Position Sheet http://www.kt.com/role/ConsolidatedStatementsofFinancialPosition Consolidated Statements of Financial Position Statements 3 false false R4.htm 9952152 - Statement - Consolidated Statements of Profit or Loss Sheet http://www.kt.com/role/ConsolidatedStatementsofProfitorLoss Consolidated Statements of Profit or Loss Statements 4 false false R5.htm 9952154 - Statement - Consolidated Statements of Comprehensive Income Sheet http://www.kt.com/role/ConsolidatedStatementsofComprehensiveIncome Consolidated Statements of Comprehensive Income Statements 5 false false R6.htm 9952156 - Statement - Consolidated Statements of Changes in Equity Sheet http://www.kt.com/role/ConsolidatedStatementsofChangesinEquity Consolidated Statements of Changes in Equity Statements 6 false false R7.htm 9952157 - Statement - Consolidated Statements of Cash Flows Sheet http://www.kt.com/role/ConsolidatedStatementsofCashFlows Consolidated Statements of Cash Flows Statements 7 false false R8.htm 9952158 - Disclosure - General Information Sheet http://www.kt.com/role/GeneralInformation General Information Notes 8 false false R9.htm 9952159 - Disclosure - Material Accounting Policies Sheet http://www.kt.com/role/MaterialAccountingPolicies Material Accounting Policies Notes 9 false false R10.htm 9952160 - Disclosure - Critical Accounting Estimates and Assumptions Sheet http://www.kt.com/role/CriticalAccountingEstimatesandAssumptions Critical Accounting Estimates and Assumptions Notes 10 false false R11.htm 9952161 - Disclosure - Financial Instruments by Category Sheet http://www.kt.com/role/FinancialInstrumentsbyCategory Financial Instruments by Category Notes 11 false false R12.htm 9952162 - Disclosure - Cash and Cash Equivalents Sheet http://www.kt.com/role/CashandCashEquivalents Cash and Cash Equivalents Notes 12 false false R13.htm 9952163 - Disclosure - Trade and Other Receivables Sheet http://www.kt.com/role/TradeandOtherReceivables Trade and Other Receivables Notes 13 false false R14.htm 9952164 - Disclosure - Other Financial Assets and Liabilities Sheet http://www.kt.com/role/OtherFinancialAssetsandLiabilities Other Financial Assets and Liabilities Notes 14 false false R15.htm 9952165 - Disclosure - Inventories Sheet http://www.kt.com/role/Inventories Inventories Notes 15 false false R16.htm 9952166 - Disclosure - Other Assets and Liabilities Sheet http://www.kt.com/role/OtherAssetsandLiabilities Other Assets and Liabilities Notes 16 false false R17.htm 9952167 - Disclosure - Assets Held-for-Sale Sheet http://www.kt.com/role/AssetsHeldforSale Assets Held-for-Sale Notes 17 false false R18.htm 9952168 - Disclosure - Property and Equipment Sheet http://www.kt.com/role/PropertyandEquipment Property and Equipment Notes 18 false false R19.htm 9952169 - Disclosure - Investment Properties Sheet http://www.kt.com/role/InvestmentProperties Investment Properties Notes 19 false false R20.htm 9952170 - Disclosure - Intangible Assets Sheet http://www.kt.com/role/IntangibleAssets Intangible Assets Notes 20 false false R21.htm 9952171 - Disclosure - Investments in Associates and Joint Ventures Sheet http://www.kt.com/role/InvestmentsinAssociatesandJointVentures Investments in Associates and Joint Ventures Notes 21 false false R22.htm 9952172 - Disclosure - Trade and Other Payables Sheet http://www.kt.com/role/TradeandOtherPayables Trade and Other Payables Notes 22 false false R23.htm 9952173 - Disclosure - Borrowings Sheet http://www.kt.com/role/Borrowings Borrowings Notes 23 false false R24.htm 9952174 - Disclosure - Provisions Sheet http://www.kt.com/role/Provisions Provisions Notes 24 false false R25.htm 9952175 - Disclosure - Net Defined Benefit Liabilities (Assets) Sheet http://www.kt.com/role/NetDefinedBenefitLiabilitiesAssets Net Defined Benefit Liabilities (Assets) Notes 25 false false R26.htm 9952176 - Disclosure - Defined Contribution Plan Sheet http://www.kt.com/role/DefinedContributionPlan Defined Contribution Plan Notes 26 false false R27.htm 9952177 - Disclosure - Commitments and Contingencies Sheet http://www.kt.com/role/CommitmentsandContingencies Commitments and Contingencies Notes 27 false false R28.htm 9952178 - Disclosure - Leases Sheet http://www.kt.com/role/Leases Leases Notes 28 false false R29.htm 9952179 - Disclosure - Share Capital Sheet http://www.kt.com/role/ShareCapital Share Capital Notes 29 false false R30.htm 9952180 - Disclosure - Retained Earnings Sheet http://www.kt.com/role/RetainedEarnings Retained Earnings Notes 30 false false R31.htm 9952181 - Disclosure - Accumulated Other Comprehensive Income and Other Components of Equity Sheet http://www.kt.com/role/AccumulatedOtherComprehensiveIncomeandOtherComponentsofEquity Accumulated Other Comprehensive Income and Other Components of Equity Notes 31 false false R32.htm 9952182 - Disclosure - Share-based Payments Sheet http://www.kt.com/role/SharebasedPayments Share-based Payments Notes 32 false false R33.htm 9952183 - Disclosure - Revenue from Contracts with Customers, Other Income and Relevant Contract Assets and Liabilities Sheet http://www.kt.com/role/RevenuefromContractswithCustomersOtherIncomeandRelevantContractAssetsandLiabilities Revenue from Contracts with Customers, Other Income and Relevant Contract Assets and Liabilities Notes 33 false false R34.htm 9952184 - Disclosure - Other Income Sheet http://www.kt.com/role/OtherIncome Other Income Notes 34 false false R35.htm 9952185 - Disclosure - Operating Expenses Sheet http://www.kt.com/role/OperatingExpenses Operating Expenses Notes 35 false false R36.htm 9952186 - Disclosure - Financial Income and Costs Sheet http://www.kt.com/role/FinancialIncomeandCosts Financial Income and Costs Notes 36 false false R37.htm 9952187 - Disclosure - Deferred Income Tax and income Tax Expense Sheet http://www.kt.com/role/DeferredIncomeTaxandincomeTaxExpense Deferred Income Tax and income Tax Expense Notes 37 false false R38.htm 9952188 - Disclosure - Earnings per Share Sheet http://www.kt.com/role/EarningsperShare Earnings per Share Notes 38 false false R39.htm 9952189 - Disclosure - Dividend Sheet http://www.kt.com/role/Dividend Dividend Notes 39 false false R40.htm 9952190 - Disclosure - Cash Generated from Operations Sheet http://www.kt.com/role/CashGeneratedfromOperations Cash Generated from Operations Notes 40 false false R41.htm 9952191 - Disclosure - Changes in Liabilities Arising from Financing Activities Sheet http://www.kt.com/role/ChangesinLiabilitiesArisingfromFinancingActivities Changes in Liabilities Arising from Financing Activities Notes 41 false false R42.htm 9952192 - Disclosure - Segment Information Sheet http://www.kt.com/role/SegmentInformation Segment Information Notes 42 false false R43.htm 9952193 - Disclosure - Related Party Transactions Sheet http://www.kt.com/role/RelatedPartyTransactions Related Party Transactions Notes 43 false false R44.htm 9952194 - Disclosure - Financial Risk Management Sheet http://www.kt.com/role/FinancialRiskManagement Financial Risk Management Notes 44 false false R45.htm 9952195 - Disclosure - Fair Value Sheet http://www.kt.com/role/FairValue Fair Value Notes 45 false false R46.htm 9952196 - Disclosure - Interests in Unconsolidated Structured Entities Sheet http://www.kt.com/role/InterestsinUnconsolidatedStructuredEntities Interests in Unconsolidated Structured Entities Notes 46 false false R47.htm 9952197 - Disclosure - Information About Non-controlling Interests Sheet http://www.kt.com/role/InformationAboutNoncontrollingInterests Information About Non-controlling Interests Notes 47 false false R48.htm 9952198 - Disclosure - Events After the Reporting Period Sheet http://www.kt.com/role/EventsAftertheReportingPeriod Events After the Reporting Period Notes 48 false false R49.htm 995447 - Disclosure - Insider Trading Policies and Procedures Sheet http://xbrl.sec.gov/ecd/role/InsiderTradingPoliciesProc Insider Trading Policies and Procedures Notes 49 false false R50.htm 995550 - Disclosure - Cybersecurity Risk Management and Strategy Disclosure Sheet http://xbrl.sec.gov/cyd/role/CybersecurityRiskManagementAndStrategyDisclosure Cybersecurity Risk Management and Strategy Disclosure Notes 50 false false R51.htm 9955511 - Disclosure - Material Accounting Policies (Policies) Sheet http://www.kt.com/role/MaterialAccountingPoliciesPolicies Material Accounting Policies (Policies) Policies http://www.kt.com/role/MaterialAccountingPolicies 51 false false R52.htm 9955512 - Disclosure - General Information (Tables) Sheet http://www.kt.com/role/GeneralInformationTables General Information (Tables) Tables http://www.kt.com/role/GeneralInformation 52 false false R53.htm 9955513 - Disclosure - Material Accounting Policies (Tables) Sheet http://www.kt.com/role/MaterialAccountingPoliciesTables Material Accounting Policies (Tables) Tables http://www.kt.com/role/MaterialAccountingPolicies 53 false false R54.htm 9955514 - Disclosure - Financial Instruments by Category (Tables) Sheet http://www.kt.com/role/FinancialInstrumentsbyCategoryTables Financial Instruments by Category (Tables) Tables http://www.kt.com/role/FinancialInstrumentsbyCategory 54 false false R55.htm 9955515 - Disclosure - Cash and Cash Equivalents (Tables) Sheet http://www.kt.com/role/CashandCashEquivalentsTables Cash and Cash Equivalents (Tables) Tables http://www.kt.com/role/CashandCashEquivalents 55 false false R56.htm 9955516 - Disclosure - Trade and Other Receivables (Tables) Sheet http://www.kt.com/role/TradeandOtherReceivablesTables Trade and Other Receivables (Tables) Tables http://www.kt.com/role/TradeandOtherReceivables 56 false false R57.htm 9955517 - Disclosure - Other Financial Assets and Liabilities (Tables) Sheet http://www.kt.com/role/OtherFinancialAssetsandLiabilitiesTables Other Financial Assets and Liabilities (Tables) Tables http://www.kt.com/role/OtherFinancialAssetsandLiabilities 57 false false R58.htm 9955518 - Disclosure - Inventories (Tables) Sheet http://www.kt.com/role/InventoriesTables Inventories (Tables) Tables http://www.kt.com/role/Inventories 58 false false R59.htm 9955519 - Disclosure - Other Assets and Liabilities (Tables) Sheet http://www.kt.com/role/OtherAssetsandLiabilitiesTables Other Assets and Liabilities (Tables) Tables http://www.kt.com/role/OtherAssetsandLiabilities 59 false false R60.htm 9955520 - Disclosure - Assets Held-for-Sale (Tables) Sheet http://www.kt.com/role/AssetsHeldforSaleTables Assets Held-for-Sale (Tables) Tables http://www.kt.com/role/AssetsHeldforSale 60 false false R61.htm 9955521 - Disclosure - Property and Equipment (Tables) Sheet http://www.kt.com/role/PropertyandEquipmentTables Property and Equipment (Tables) Tables http://www.kt.com/role/PropertyandEquipment 61 false false R62.htm 9955522 - Disclosure - Investment Properties (Tables) Sheet http://www.kt.com/role/InvestmentPropertiesTables Investment Properties (Tables) Tables http://www.kt.com/role/InvestmentProperties 62 false false R63.htm 9955523 - Disclosure - Intangible Assets (Tables) Sheet http://www.kt.com/role/IntangibleAssetsTables Intangible Assets (Tables) Tables http://www.kt.com/role/IntangibleAssets 63 false false R64.htm 9955524 - Disclosure - Investments in Associates and Joint Ventures (Tables) Sheet http://www.kt.com/role/InvestmentsinAssociatesandJointVenturesTables Investments in Associates and Joint Ventures (Tables) Tables http://www.kt.com/role/InvestmentsinAssociatesandJointVentures 64 false false R65.htm 9955525 - Disclosure - Trade and Other Payables (Tables) Sheet http://www.kt.com/role/TradeandOtherPayablesTables Trade and Other Payables (Tables) Tables http://www.kt.com/role/TradeandOtherPayables 65 false false R66.htm 9955526 - Disclosure - Borrowings (Tables) Sheet http://www.kt.com/role/BorrowingsTables Borrowings (Tables) Tables http://www.kt.com/role/Borrowings 66 false false R67.htm 9955527 - Disclosure - Provisions (Tables) Sheet http://www.kt.com/role/ProvisionsTables Provisions (Tables) Tables http://www.kt.com/role/Provisions 67 false false R68.htm 9955528 - Disclosure - Net Defined Benefit Liabilities (Assets) (Tables) Sheet http://www.kt.com/role/NetDefinedBenefitLiabilitiesAssetsTables Net Defined Benefit Liabilities (Assets) (Tables) Tables http://www.kt.com/role/NetDefinedBenefitLiabilitiesAssets 68 false false R69.htm 9955529 - Disclosure - Commitments and Contingencies (Tables) Sheet http://www.kt.com/role/CommitmentsandContingenciesTables Commitments and Contingencies (Tables) Tables http://www.kt.com/role/CommitmentsandContingencies 69 false false R70.htm 9955530 - Disclosure - Leases (Tables) Sheet http://www.kt.com/role/LeasesTables Leases (Tables) Tables http://www.kt.com/role/Leases 70 false false R71.htm 9955531 - Disclosure - Share Capital (Tables) Sheet http://www.kt.com/role/ShareCapitalTables Share Capital (Tables) Tables http://www.kt.com/role/ShareCapital 71 false false R72.htm 9955532 - Disclosure - Retained Earnings (Tables) Sheet http://www.kt.com/role/RetainedEarningsTables Retained Earnings (Tables) Tables http://www.kt.com/role/RetainedEarnings 72 false false R73.htm 9955533 - Disclosure - Accumulated Other Comprehensive Income and Other Components of Equity (Tables) Sheet http://www.kt.com/role/AccumulatedOtherComprehensiveIncomeandOtherComponentsofEquityTables Accumulated Other Comprehensive Income and Other Components of Equity (Tables) Tables http://www.kt.com/role/AccumulatedOtherComprehensiveIncomeandOtherComponentsofEquity 73 false false R74.htm 9955534 - Disclosure - Share-based Payments (Tables) Sheet http://www.kt.com/role/SharebasedPaymentsTables Share-based Payments (Tables) Tables http://www.kt.com/role/SharebasedPayments 74 false false R75.htm 9955535 - Disclosure - Revenue from Contracts with Customers, Other Income and Relevant Contract Assets and Liabilities (Tables) Sheet http://www.kt.com/role/RevenuefromContractswithCustomersOtherIncomeandRelevantContractAssetsandLiabilitiesTables Revenue from Contracts with Customers, Other Income and Relevant Contract Assets and Liabilities (Tables) Tables http://www.kt.com/role/RevenuefromContractswithCustomersOtherIncomeandRelevantContractAssetsandLiabilities 75 false false R76.htm 9955536 - Disclosure - Other Income (Tables) Sheet http://www.kt.com/role/OtherIncomeTables Other Income (Tables) Tables http://www.kt.com/role/OtherIncome 76 false false R77.htm 9955537 - Disclosure - Operating Expenses (Tables) Sheet http://www.kt.com/role/OperatingExpensesTables Operating Expenses (Tables) Tables http://www.kt.com/role/OperatingExpenses 77 false false R78.htm 9955538 - Disclosure - Financial Income and Costs (Tables) Sheet http://www.kt.com/role/FinancialIncomeandCostsTables Financial Income and Costs (Tables) Tables http://www.kt.com/role/FinancialIncomeandCosts 78 false false R79.htm 9955539 - Disclosure - Deferred Income Tax and income Tax Expense (Tables) Sheet http://www.kt.com/role/DeferredIncomeTaxandincomeTaxExpenseTables Deferred Income Tax and income Tax Expense (Tables) Tables http://www.kt.com/role/DeferredIncomeTaxandincomeTaxExpense 79 false false R80.htm 9955540 - Disclosure - Earnings per Share (Tables) Sheet http://www.kt.com/role/EarningsperShareTables Earnings per Share (Tables) Tables http://www.kt.com/role/EarningsperShare 80 false false R81.htm 9955541 - Disclosure - Cash Generated from Operations (Tables) Sheet http://www.kt.com/role/CashGeneratedfromOperationsTables Cash Generated from Operations (Tables) Tables http://www.kt.com/role/CashGeneratedfromOperations 81 false false R82.htm 9955542 - Disclosure - Changes in Liabilities Arising from Financing Activities (Tables) Sheet http://www.kt.com/role/ChangesinLiabilitiesArisingfromFinancingActivitiesTables Changes in Liabilities Arising from Financing Activities (Tables) Tables http://www.kt.com/role/ChangesinLiabilitiesArisingfromFinancingActivities 82 false false R83.htm 9955543 - Disclosure - Segment Information (Tables) Sheet http://www.kt.com/role/SegmentInformationTables Segment Information (Tables) Tables http://www.kt.com/role/SegmentInformation 83 false false R84.htm 9955544 - Disclosure - Related Party Transactions (Tables) Sheet http://www.kt.com/role/RelatedPartyTransactionsTables Related Party Transactions (Tables) Tables http://www.kt.com/role/RelatedPartyTransactions 84 false false R85.htm 9955545 - Disclosure - Financial Risk Management (Tables) Sheet http://www.kt.com/role/FinancialRiskManagementTables Financial Risk Management (Tables) Tables http://www.kt.com/role/FinancialRiskManagement 85 false false R86.htm 9955546 - Disclosure - Fair Value (Tables) Sheet http://www.kt.com/role/FairValueTables Fair Value (Tables) Tables http://www.kt.com/role/FairValue 86 false false R87.htm 9955547 - Disclosure - Interests in Unconsolidated Structured Entities (Tables) Sheet http://www.kt.com/role/InterestsinUnconsolidatedStructuredEntitiesTables Interests in Unconsolidated Structured Entities (Tables) Tables http://www.kt.com/role/InterestsinUnconsolidatedStructuredEntities 87 false false R88.htm 9955548 - Disclosure - Information About Non-controlling Interests (Tables) Sheet http://www.kt.com/role/InformationAboutNoncontrollingInterestsTables Information About Non-controlling Interests (Tables) Tables http://www.kt.com/role/InformationAboutNoncontrollingInterests 88 false false R89.htm 9955549 - Disclosure - Events After the Reporting Period (Tables) Sheet http://www.kt.com/role/EventsAftertheReportingPeriodTables Events After the Reporting Period (Tables) Tables http://www.kt.com/role/EventsAftertheReportingPeriod 89 false false R90.htm 9955550 - Disclosure - General Information - Additional Information (Details) Sheet http://www.kt.com/role/GeneralInformationAdditionalInformationDetails General Information - Additional Information (Details) Details 90 false false R91.htm 9955551 - Disclosure - General Information - Schedule of Consolidated Subsidiaries - Controlling Interest (Details) Sheet http://www.kt.com/role/GeneralInformationScheduleofConsolidatedSubsidiariesControllingInterestDetails General Information - Schedule of Consolidated Subsidiaries - Controlling Interest (Details) Details 91 false false R92.htm 9955552 - Disclosure - General Information - Schedule of Assets and Income per Subsidiary (Details) Sheet http://www.kt.com/role/GeneralInformationScheduleofAssetsandIncomeperSubsidiaryDetails General Information - Schedule of Assets and Income per Subsidiary (Details) Details 92 false false R93.htm 9955553 - Disclosure - Material Accounting Policies - Additional Information (Details) Sheet http://www.kt.com/role/MaterialAccountingPoliciesAdditionalInformationDetails Material Accounting Policies - Additional Information (Details) Details 93 false false R94.htm 9955554 - Disclosure - Material Accounting Policies - Summary of Estimated Useful Lives of Property, Plant and Equipment (Details) Sheet http://www.kt.com/role/MaterialAccountingPoliciesSummaryofEstimatedUsefulLivesofPropertyPlantandEquipmentDetails Material Accounting Policies - Summary of Estimated Useful Lives of Property, Plant and Equipment (Details) Details 94 false false R95.htm 9955555 - Disclosure - Material Accounting Policies - Summary of Amortization of Intangible Assets With Limited Useful Life (Details) Sheet http://www.kt.com/role/MaterialAccountingPoliciesSummaryofAmortizationofIntangibleAssetsWithLimitedUsefulLifeDetails Material Accounting Policies - Summary of Amortization of Intangible Assets With Limited Useful Life (Details) Details 95 false false R96.htm 9955556 - Disclosure - Financial Instruments by Category - Schedule of Financial Instruments by Category (Details) Sheet http://www.kt.com/role/FinancialInstrumentsbyCategoryScheduleofFinancialInstrumentsbyCategoryDetails Financial Instruments by Category - Schedule of Financial Instruments by Category (Details) Details 96 false false R97.htm 9955557 - Disclosure - Financial Instruments by Category - Schedule of Gains or Losses Arising From Financial Instruments by Category (Details) Sheet http://www.kt.com/role/FinancialInstrumentsbyCategoryScheduleofGainsorLossesArisingFromFinancialInstrumentsbyCategoryDetails Financial Instruments by Category - Schedule of Gains or Losses Arising From Financial Instruments by Category (Details) Details 97 false false R98.htm 9955558 - Disclosure - Cash and Cash Equivalents to Restricted Cash - Schedule of Restricted Cash and Cash Equivalents (Details) Sheet http://www.kt.com/role/CashandCashEquivalentstoRestrictedCashScheduleofRestrictedCashandCashEquivalentsDetails Cash and Cash Equivalents to Restricted Cash - Schedule of Restricted Cash and Cash Equivalents (Details) Details 98 false false R99.htm 9955559 - Disclosure - Trade and Other Receivables - Schedule of Trade and Other Receivables (Details) Sheet http://www.kt.com/role/TradeandOtherReceivablesScheduleofTradeandOtherReceivablesDetails Trade and Other Receivables - Schedule of Trade and Other Receivables (Details) Details 99 false false R100.htm 9955560 - Disclosure - Trade and Other Receivables - Schedule of Changes in Summary of Changes in Provision for Impairment (Details) Sheet http://www.kt.com/role/TradeandOtherReceivablesScheduleofChangesinSummaryofChangesinProvisionforImpairmentDetails Trade and Other Receivables - Schedule of Changes in Summary of Changes in Provision for Impairment (Details) Details 100 false false R101.htm 9955561 - Disclosure - Trade and Other Receivables - Schedule of Other Receivables (Details) Sheet http://www.kt.com/role/TradeandOtherReceivablesScheduleofOtherReceivablesDetails Trade and Other Receivables - Schedule of Other Receivables (Details) Details 101 false false R102.htm 9955562 - Disclosure - Other Financial Assets and Liabilities - Schedule of Other Financial Assets and Liabilities (Details) Sheet http://www.kt.com/role/OtherFinancialAssetsandLiabilitiesScheduleofOtherFinancialAssetsandLiabilitiesDetails Other Financial Assets and Liabilities - Schedule of Other Financial Assets and Liabilities (Details) Details 102 false false R103.htm 9955563 - Disclosure - Other Financial Assets and Liabilities - Schedule of Financial Assets at Fair Value Through Profit or Loss (Details) Sheet http://www.kt.com/role/OtherFinancialAssetsandLiabilitiesScheduleofFinancialAssetsatFairValueThroughProfitorLossDetails Other Financial Assets and Liabilities - Schedule of Financial Assets at Fair Value Through Profit or Loss (Details) Details 103 false false R104.htm 9955564 - Disclosure - Other Financial Assets and Liabilities - Schedule of Financial Assets at Fair Value Through Other Comprehensive Income (Details) Sheet http://www.kt.com/role/OtherFinancialAssetsandLiabilitiesScheduleofFinancialAssetsatFairValueThroughOtherComprehensiveIncomeDetails Other Financial Assets and Liabilities - Schedule of Financial Assets at Fair Value Through Other Comprehensive Income (Details) Details 104 false false R105.htm 9955565 - Disclosure - Other Financial Assets and Liabilities - Schedule of Derivative Financial Assets and Liabilities (Details) Sheet http://www.kt.com/role/OtherFinancialAssetsandLiabilitiesScheduleofDerivativeFinancialAssetsandLiabilitiesDetails Other Financial Assets and Liabilities - Schedule of Derivative Financial Assets and Liabilities (Details) Details 105 false false R106.htm 9955566 - Disclosure - Other Financial Assets and Liabilities - Schedule of Valuation Gains and Losses on Derivatives Contracts (Details) Sheet http://www.kt.com/role/OtherFinancialAssetsandLiabilitiesScheduleofValuationGainsandLossesonDerivativesContractsDetails Other Financial Assets and Liabilities - Schedule of Valuation Gains and Losses on Derivatives Contracts (Details) Details 106 false false R107.htm 9955567 - Disclosure - Other Financial Assets and Liabilities - Additional Information (Details) Sheet http://www.kt.com/role/OtherFinancialAssetsandLiabilitiesAdditionalInformationDetails Other Financial Assets and Liabilities - Additional Information (Details) Details 107 false false R108.htm 9955568 - Disclosure - Other Financial Assets and Liabilities - Schedule of Hedging instruments (Details) Sheet http://www.kt.com/role/OtherFinancialAssetsandLiabilitiesScheduleofHedginginstrumentsDetails Other Financial Assets and Liabilities - Schedule of Hedging instruments (Details) Details 108 false false R109.htm 9955569 - Disclosure - Other Financial Assets and Liabilities - Schedule of Hedged items (Details) Sheet http://www.kt.com/role/OtherFinancialAssetsandLiabilitiesScheduleofHedgeditemsDetails Other Financial Assets and Liabilities - Schedule of Hedged items (Details) Details 109 false false R110.htm 9955570 - Disclosure - Other Financial Assets and Liabilities - Schedule of Financial Liabilities at Fair Value Through Profit or Loss (Details) Sheet http://www.kt.com/role/OtherFinancialAssetsandLiabilitiesScheduleofFinancialLiabilitiesatFairValueThroughProfitorLossDetails Other Financial Assets and Liabilities - Schedule of Financial Liabilities at Fair Value Through Profit or Loss (Details) Details 110 false false R111.htm 9955571 - Disclosure - Other Financial Assets and Liabilities - Schedule of Valuation Gain and Loss on Financial Liabilities at Fair Value Through Profit or Loss (Details) Sheet http://www.kt.com/role/OtherFinancialAssetsandLiabilitiesScheduleofValuationGainandLossonFinancialLiabilitiesatFairValueThroughProfitorLossDetails Other Financial Assets and Liabilities - Schedule of Valuation Gain and Loss on Financial Liabilities at Fair Value Through Profit or Loss (Details) Details 111 false false R112.htm 9955572 - Disclosure - Inventories - Schedule of Inventories Net (Details) Sheet http://www.kt.com/role/InventoriesScheduleofInventoriesNetDetails Inventories - Schedule of Inventories Net (Details) Details 112 false false R113.htm 9955573 - Disclosure - Inventories - Additional Information (Details) Sheet http://www.kt.com/role/InventoriesAdditionalInformationDetails Inventories - Additional Information (Details) Details 113 false false R114.htm 9955574 - Disclosure - Other Assets and Liabilities - Schedule of Other Assets and Liabilities (Details) Sheet http://www.kt.com/role/OtherAssetsandLiabilitiesScheduleofOtherAssetsandLiabilitiesDetails Other Assets and Liabilities - Schedule of Other Assets and Liabilities (Details) Details 114 false false R115.htm 9955575 - Disclosure - Assets Held-for-Sale - Additional Information (Details) Sheet http://www.kt.com/role/AssetsHeldforSaleAdditionalInformationDetails Assets Held-for-Sale - Additional Information (Details) Details 115 false false R116.htm 9955576 - Disclosure - Assets Held-for-Sale - Schedule of Assets not Disposed (Details) Sheet http://www.kt.com/role/AssetsHeldforSaleScheduleofAssetsnotDisposedDetails Assets Held-for-Sale - Schedule of Assets not Disposed (Details) Details 116 false false R117.htm 9955577 - Disclosure - Property and Equipment - Schedule of Changes in Property and Equipment (Details) Sheet http://www.kt.com/role/PropertyandEquipmentScheduleofChangesinPropertyandEquipmentDetails Property and Equipment - Schedule of Changes in Property and Equipment (Details) Details 117 false false R118.htm 9955578 - Disclosure - Property and Equipment - Additional Information (Details) Sheet http://www.kt.com/role/PropertyandEquipmentAdditionalInformationDetails Property and Equipment - Additional Information (Details) Details 118 false false R119.htm 9955579 - Disclosure - Investment Properties - Schedule of Investment Properties (Details) Sheet http://www.kt.com/role/InvestmentPropertiesScheduleofInvestmentPropertiesDetails Investment Properties - Schedule of Investment Properties (Details) Details 119 false false R120.htm 9955580 - Disclosure - Investment Properties - Additional Information (Details) Sheet http://www.kt.com/role/InvestmentPropertiesAdditionalInformationDetails Investment Properties - Additional Information (Details) Details 120 false false R121.htm 9955581 - Disclosure - Intangible Assets - Schedule of Intangible Assets (Details) Sheet http://www.kt.com/role/IntangibleAssetsScheduleofIntangibleAssetsDetails Intangible Assets - Schedule of Intangible Assets (Details) Details 121 false false R122.htm 9955582 - Disclosure - Intangible Assets - Additional Information (Details) Sheet http://www.kt.com/role/IntangibleAssetsAdditionalInformationDetails Intangible Assets - Additional Information (Details) Details 122 false false R123.htm 9955583 - Disclosure - Intangible Assets - Schedule of Goodwill Allocated to Each Cash-Generation Unit (Details) Sheet http://www.kt.com/role/IntangibleAssetsScheduleofGoodwillAllocatedtoEachCashGenerationUnitDetails Intangible Assets - Schedule of Goodwill Allocated to Each Cash-Generation Unit (Details) Details 123 false false R124.htm 9955584 - Disclosure - Investments in Associates and Joint Ventures - Schedule of Details of Associates (Details) Sheet http://www.kt.com/role/InvestmentsinAssociatesandJointVenturesScheduleofDetailsofAssociatesDetails Investments in Associates and Joint Ventures - Schedule of Details of Associates (Details) Details 124 false false R125.htm 9955585 - Disclosure - Investments in Associates and Joint Ventures - Schedule of Changes in Investments in Associates and Joint Ventures (Details) Sheet http://www.kt.com/role/InvestmentsinAssociatesandJointVenturesScheduleofChangesinInvestmentsinAssociatesandJointVenturesDetails Investments in Associates and Joint Ventures - Schedule of Changes in Investments in Associates and Joint Ventures (Details) Details 125 false false R126.htm 9955586 - Disclosure - Investments in Associates and Joint Ventures - Schedule of Financial Information of Associates and Joint Ventures (Details) Sheet http://www.kt.com/role/InvestmentsinAssociatesandJointVenturesScheduleofFinancialInformationofAssociatesandJointVenturesDetails Investments in Associates and Joint Ventures - Schedule of Financial Information of Associates and Joint Ventures (Details) Details 126 false false R127.htm 9955587 - Disclosure - Investments in Associates and Joint Ventures - Schedule of Reconciliation of Carrying Amount of Interests in the Associates and Joint Ventures (Details) Sheet http://www.kt.com/role/InvestmentsinAssociatesandJointVenturesScheduleofReconciliationofCarryingAmountofInterestsintheAssociatesandJointVenturesDetails Investments in Associates and Joint Ventures - Schedule of Reconciliation of Carrying Amount of Interests in the Associates and Joint Ventures (Details) Details 127 false false R128.htm 9955588 - Disclosure - Investments in Associates and Joint Ventures - Additional Information (Details) Sheet http://www.kt.com/role/InvestmentsinAssociatesandJointVenturesAdditionalInformationDetails Investments in Associates and Joint Ventures - Additional Information (Details) Details 128 false false R129.htm 9955589 - Disclosure - Trade and Other Payables - Schedule of Trade and Other Payables (Details) Sheet http://www.kt.com/role/TradeandOtherPayablesScheduleofTradeandOtherPayablesDetails Trade and Other Payables - Schedule of Trade and Other Payables (Details) Details 129 false false R130.htm 9955590 - Disclosure - Trade and Other Payables - Schedule of Other Payables (Details) Sheet http://www.kt.com/role/TradeandOtherPayablesScheduleofOtherPayablesDetails Trade and Other Payables - Schedule of Other Payables (Details) Details 130 false false R131.htm 9955591 - Disclosure - Borrowings - Schedule of Borrowings (Details) Sheet http://www.kt.com/role/BorrowingsScheduleofBorrowingsDetails Borrowings - Schedule of Borrowings (Details) Details 131 false false R132.htm 9955592 - Disclosure - Borrowings - Schedule of Korean Won and Foreign Currency Borrowings (Details) Sheet http://www.kt.com/role/BorrowingsScheduleofKoreanWonandForeignCurrencyBorrowingsDetails Borrowings - Schedule of Korean Won and Foreign Currency Borrowings (Details) Details 132 false false R133.htm 9955593 - Disclosure - Borrowings - Schedule of Short-term Borrowing (Details) Sheet http://www.kt.com/role/BorrowingsScheduleofShorttermBorrowingDetails Borrowings - Schedule of Short-term Borrowing (Details) Details 133 false false R134.htm 9955594 - Disclosure - Borrowings - Schedule of Long-term Borrowings (Details) Sheet http://www.kt.com/role/BorrowingsScheduleofLongtermBorrowingsDetails Borrowings - Schedule of Long-term Borrowings (Details) Details 134 false false R135.htm 9955595 - Disclosure - Borrowings - Schedule of Repayment of Debentures and Borrowings Including the Current Liabilities (Details) Sheet http://www.kt.com/role/BorrowingsScheduleofRepaymentofDebenturesandBorrowingsIncludingtheCurrentLiabilitiesDetails Borrowings - Schedule of Repayment of Debentures and Borrowings Including the Current Liabilities (Details) Details 135 false false R136.htm 9955596 - Disclosure - Provisions - Schedule of Changes in Provisions (Details) Sheet http://www.kt.com/role/ProvisionsScheduleofChangesinProvisionsDetails Provisions - Schedule of Changes in Provisions (Details) Details 136 false false R137.htm 9955597 - Disclosure - Net Defined Benefit Liabilities (Assets) - Schedule of Amount Recognized in the Statements of Financial Position (Details) Sheet http://www.kt.com/role/NetDefinedBenefitLiabilitiesAssetsScheduleofAmountRecognizedintheStatementsofFinancialPositionDetails Net Defined Benefit Liabilities (Assets) - Schedule of Amount Recognized in the Statements of Financial Position (Details) Details http://www.kt.com/role/NetDefinedBenefitLiabilitiesAssetsTables 137 false false R138.htm 9955598 - Disclosure - Net Defined Benefit Liabilities (Assets) - Schedule of Changes in the Defined Benefit Obligations (Details) Sheet http://www.kt.com/role/NetDefinedBenefitLiabilitiesAssetsScheduleofChangesintheDefinedBenefitObligationsDetails Net Defined Benefit Liabilities (Assets) - Schedule of Changes in the Defined Benefit Obligations (Details) Details http://www.kt.com/role/NetDefinedBenefitLiabilitiesAssetsTables 138 false false R139.htm 9955599 - Disclosure - Net Defined Benefit Liabilities (Assets) - Schedule of Changes in the Fair Value of Plan Assets (Details) Sheet http://www.kt.com/role/NetDefinedBenefitLiabilitiesAssetsScheduleofChangesintheFairValueofPlanAssetsDetails Net Defined Benefit Liabilities (Assets) - Schedule of Changes in the Fair Value of Plan Assets (Details) Details http://www.kt.com/role/NetDefinedBenefitLiabilitiesAssetsTables 139 false false R140.htm 9955600 - Disclosure - Net Defined Benefit Liabilities (Assets) - Schedule of Amounts Recognized in the Consolidated Statements of Operations (Details) Sheet http://www.kt.com/role/NetDefinedBenefitLiabilitiesAssetsScheduleofAmountsRecognizedintheConsolidatedStatementsofOperationsDetails Net Defined Benefit Liabilities (Assets) - Schedule of Amounts Recognized in the Consolidated Statements of Operations (Details) Details http://www.kt.com/role/NetDefinedBenefitLiabilitiesAssetsTables 140 false false R141.htm 9955601 - Disclosure - Net Defined Benefit Liabilities (Assets) - Schedule of Principal Actuarial Assumptions (Details) Sheet http://www.kt.com/role/NetDefinedBenefitLiabilitiesAssetsScheduleofPrincipalActuarialAssumptionsDetails Net Defined Benefit Liabilities (Assets) - Schedule of Principal Actuarial Assumptions (Details) Details http://www.kt.com/role/NetDefinedBenefitLiabilitiesAssetsTables 141 false false R142.htm 9955602 - Disclosure - Net Defined Benefit Liabilities (Assets) - Schedule of Sensitivity of the Defined Benefit Obligations (Details) Sheet http://www.kt.com/role/NetDefinedBenefitLiabilitiesAssetsScheduleofSensitivityoftheDefinedBenefitObligationsDetails Net Defined Benefit Liabilities (Assets) - Schedule of Sensitivity of the Defined Benefit Obligations (Details) Details http://www.kt.com/role/NetDefinedBenefitLiabilitiesAssetsTables 142 false false R143.htm 9955603 - Disclosure - Net Defined Benefit Liabilities (Assets) - Additional Information (Details) Sheet http://www.kt.com/role/NetDefinedBenefitLiabilitiesAssetsAdditionalInformationDetails Net Defined Benefit Liabilities (Assets) - Additional Information (Details) Details http://www.kt.com/role/NetDefinedBenefitLiabilitiesAssetsTables 143 false false R144.htm 9955604 - Disclosure - Net Defined Benefit Liabilities (Assets) - Schedule of Expected Maturity Analysis of Undiscounted Pension Benefits (Details) Sheet http://www.kt.com/role/NetDefinedBenefitLiabilitiesAssetsScheduleofExpectedMaturityAnalysisofUndiscountedPensionBenefitsDetails Net Defined Benefit Liabilities (Assets) - Schedule of Expected Maturity Analysis of Undiscounted Pension Benefits (Details) Details http://www.kt.com/role/NetDefinedBenefitLiabilitiesAssetsTables 144 false false R145.htm 9955605 - Disclosure - Defined Contribution Plan (Details) Sheet http://www.kt.com/role/DefinedContributionPlanDetails Defined Contribution Plan (Details) Details http://www.kt.com/role/DefinedContributionPlan 145 false false R146.htm 9955606 - Disclosure - Commitments and Contingencies - Schedule of Major Commitments with Local Financial Institutions (Details) Sheet http://www.kt.com/role/CommitmentsandContingenciesScheduleofMajorCommitmentswithLocalFinancialInstitutionsDetails Commitments and Contingencies - Schedule of Major Commitments with Local Financial Institutions (Details) Details 146 false false R147.htm 9955607 - Disclosure - Commitments and Contingencies - Schedule of Guarantees Received from Financial Institutions (Details) Sheet http://www.kt.com/role/CommitmentsandContingenciesScheduleofGuaranteesReceivedfromFinancialInstitutionsDetails Commitments and Contingencies - Schedule of Guarantees Received from Financial Institutions (Details) Details 147 false false R148.htm 9955608 - Disclosure - Commitments and Contingencies - Additional Information (Details) Sheet http://www.kt.com/role/CommitmentsandContingenciesAdditionalInformationDetails Commitments and Contingencies - Additional Information (Details) Details 148 false false R149.htm 9955609 - Disclosure - Commitments and Contingencies - Schedule of Investment Properties Provided as Collateral (Detail) Sheet http://www.kt.com/role/CommitmentsandContingenciesScheduleofInvestmentPropertiesProvidedasCollateralDetail Commitments and Contingencies - Schedule of Investment Properties Provided as Collateral (Detail) Details 149 false false R150.htm 9955610 - Disclosure - Leases - Schedule of Balance sheet Information About Leases for Lessee (Details) Sheet http://www.kt.com/role/LeasesScheduleofBalancesheetInformationAboutLeasesforLesseeDetails Leases - Schedule of Balance sheet Information About Leases for Lessee (Details) Details 150 false false R151.htm 9955611 - Disclosure - Leases - Additional Information (Details) Sheet http://www.kt.com/role/LeasesAdditionalInformationDetails Leases - Additional Information (Details) Details 151 false false R152.htm 9955612 - Disclosure - Leases - Schedule of Statement of Profit or Loss Information About Leases for Lessee (Details) Sheet http://www.kt.com/role/LeasesScheduleofStatementofProfitorLossInformationAboutLeasesforLesseeDetails Leases - Schedule of Statement of Profit or Loss Information About Leases for Lessee (Details) Details 152 false false R153.htm 9955613 - Disclosure - Share Capital - Additional Information (Details) Sheet http://www.kt.com/role/ShareCapitalAdditionalInformationDetails Share Capital - Additional Information (Details) Details 153 false false R154.htm 9955614 - Disclosure - Share Capital - Schedule of Share Capital (Details) Sheet http://www.kt.com/role/ShareCapitalScheduleofShareCapitalDetails Share Capital - Schedule of Share Capital (Details) Details 154 false false R155.htm 9955615 - Disclosure - Retained Earnings - Schedule of Retained Earnings (Details) Sheet http://www.kt.com/role/RetainedEarningsScheduleofRetainedEarningsDetails Retained Earnings - Schedule of Retained Earnings (Details) Details 155 false false R156.htm 9955616 - Disclosure - Accumulated Other Comprehensive Income and Other Components of Equity - Schedule of Accumulated Other Comprehensive Income (Details) Sheet http://www.kt.com/role/AccumulatedOtherComprehensiveIncomeandOtherComponentsofEquityScheduleofAccumulatedOtherComprehensiveIncomeDetails Accumulated Other Comprehensive Income and Other Components of Equity - Schedule of Accumulated Other Comprehensive Income (Details) Details 156 false false R157.htm 9955617 - Disclosure - Accumulated Other Comprehensive Income and Other Components of Equity - Schedule of Changes in Accumulated Other Comprehensive Income (Details) Sheet http://www.kt.com/role/AccumulatedOtherComprehensiveIncomeandOtherComponentsofEquityScheduleofChangesinAccumulatedOtherComprehensiveIncomeDetails Accumulated Other Comprehensive Income and Other Components of Equity - Schedule of Changes in Accumulated Other Comprehensive Income (Details) Details 157 false false R158.htm 9955618 - Disclosure - Accumulated Other Comprehensive Income and Other Components of Equity - Schedule of Other Components of Equity (Details) Sheet http://www.kt.com/role/AccumulatedOtherComprehensiveIncomeandOtherComponentsofEquityScheduleofOtherComponentsofEquityDetails Accumulated Other Comprehensive Income and Other Components of Equity - Schedule of Other Components of Equity (Details) Details 158 false false R159.htm 9955619 - Disclosure - Accumulated Other Comprehensive Income and Other Components of Equity - Schedule of Treasury Stock (Details) Sheet http://www.kt.com/role/AccumulatedOtherComprehensiveIncomeandOtherComponentsofEquityScheduleofTreasuryStockDetails Accumulated Other Comprehensive Income and Other Components of Equity - Schedule of Treasury Stock (Details) Details 159 false false R160.htm 9955620 - Disclosure - Share-based Payments - Schedule of Details of Share-based Payments (Details) Sheet http://www.kt.com/role/SharebasedPaymentsScheduleofDetailsofSharebasedPaymentsDetails Share-based Payments - Schedule of Details of Share-based Payments (Details) Details 160 false false R161.htm 9955621 - Disclosure - Share-based Payments - Schedule of Changes in the Number of Stock Options and the Weighted-Average Exercise Price (Details) Sheet http://www.kt.com/role/SharebasedPaymentsScheduleofChangesintheNumberofStockOptionsandtheWeightedAverageExercisePriceDetails Share-based Payments - Schedule of Changes in the Number of Stock Options and the Weighted-Average Exercise Price (Details) Details 161 false false R162.htm 9955622 - Disclosure - Share-based Payments - Schedule of Changes in the Number of Equity Instruments Other Than Options and the Weighted-Average Exercise Price (Details) Sheet http://www.kt.com/role/SharebasedPaymentsScheduleofChangesintheNumberofEquityInstrumentsOtherThanOptionsandtheWeightedAverageExercisePriceDetails Share-based Payments - Schedule of Changes in the Number of Equity Instruments Other Than Options and the Weighted-Average Exercise Price (Details) Details 162 false false R163.htm 9955623 - Disclosure - Revenue from Contracts with Customers, Other Income and Relevant Contract Assets and Liabilities - Schedule of Revenue And Other Income in the Statement of Profit or Loss (Details) Sheet http://www.kt.com/role/RevenuefromContractswithCustomersOtherIncomeandRelevantContractAssetsandLiabilitiesScheduleofRevenueAndOtherIncomeintheStatementofProfitorLossDetails Revenue from Contracts with Customers, Other Income and Relevant Contract Assets and Liabilities - Schedule of Revenue And Other Income in the Statement of Profit or Loss (Details) Details 163 false false R164.htm 9955624 - Disclosure - Revenue from Contracts with Customers, Other Income and Relevant Contract Assets and Liabilities - Schedule of Operating Revenues and Other Income (Details) Sheet http://www.kt.com/role/RevenuefromContractswithCustomersOtherIncomeandRelevantContractAssetsandLiabilitiesScheduleofOperatingRevenuesandOtherIncomeDetails Revenue from Contracts with Customers, Other Income and Relevant Contract Assets and Liabilities - Schedule of Operating Revenues and Other Income (Details) Details 164 false false R165.htm 9955625 - Disclosure - Revenue from Contracts with Customers, Other Income and Relevant Contract Assets and Liabilities - Schedule of Contract with Customer Assets and Liabilities (Details) Sheet http://www.kt.com/role/RevenuefromContractswithCustomersOtherIncomeandRelevantContractAssetsandLiabilitiesScheduleofContractwithCustomerAssetsandLiabilitiesDetails Revenue from Contracts with Customers, Other Income and Relevant Contract Assets and Liabilities - Schedule of Contract with Customer Assets and Liabilities (Details) Details 165 false false R166.htm 9955626 - Disclosure - Revenue from Contracts with Customers, Other Income and Relevant Contract Assets and Liabilities - Schedule of Contract Costs Recognized as Assets (Details) Sheet http://www.kt.com/role/RevenuefromContractswithCustomersOtherIncomeandRelevantContractAssetsandLiabilitiesScheduleofContractCostsRecognizedasAssetsDetails Revenue from Contracts with Customers, Other Income and Relevant Contract Assets and Liabilities - Schedule of Contract Costs Recognized as Assets (Details) Details 166 false false R167.htm 9955627 - Disclosure - Revenue from Contracts with Customers, Other Income and Relevant Contract Assets and Liabilities - Additional Information (Details) Sheet http://www.kt.com/role/RevenuefromContractswithCustomersOtherIncomeandRelevantContractAssetsandLiabilitiesAdditionalInformationDetails Revenue from Contracts with Customers, Other Income and Relevant Contract Assets and Liabilities - Additional Information (Details) Details 167 false false R168.htm 9955628 - Disclosure - Revenue from Contracts with Customers, Other Income and Relevant Contract Assets and Liabilities - Schedule of Revenue Recognized from Carried-Forward Contract Liabilities (Details) Sheet http://www.kt.com/role/RevenuefromContractswithCustomersOtherIncomeandRelevantContractAssetsandLiabilitiesScheduleofRevenueRecognizedfromCarriedForwardContractLiabilitiesDetails Revenue from Contracts with Customers, Other Income and Relevant Contract Assets and Liabilities - Schedule of Revenue Recognized from Carried-Forward Contract Liabilities (Details) Details 168 false false R169.htm 9955629 - Disclosure - Other Income - Schedule of Other Income (Details) Sheet http://www.kt.com/role/OtherIncomeScheduleofOtherIncomeDetails Other Income - Schedule of Other Income (Details) Details 169 false false R170.htm 9955630 - Disclosure - Operating Expenses - Schedule of Operating Expenses (Details) Sheet http://www.kt.com/role/OperatingExpensesScheduleofOperatingExpensesDetails Operating Expenses - Schedule of Operating Expenses (Details) Details 170 false false R171.htm 9955631 - Disclosure - Operating Expenses - Schedule of Employee Benefits (Details) Sheet http://www.kt.com/role/OperatingExpensesScheduleofEmployeeBenefitsDetails Operating Expenses - Schedule of Employee Benefits (Details) Details 171 false false R172.htm 9955632 - Disclosure - Financial Income and Costs - Schedule of Financial Income (Details) Sheet http://www.kt.com/role/FinancialIncomeandCostsScheduleofFinancialIncomeDetails Financial Income and Costs - Schedule of Financial Income (Details) Details 172 false false R173.htm 9955633 - Disclosure - Financial Income and Costs - Schedule of Financial Costs (Details) Sheet http://www.kt.com/role/FinancialIncomeandCostsScheduleofFinancialCostsDetails Financial Income and Costs - Schedule of Financial Costs (Details) Details 173 false false R174.htm 9955634 - Disclosure - Deferred Income Tax and income Tax Expense - Schedule of Analysis of Deferred Tax Assets and Deferred Tax Liabilities (Details) Sheet http://www.kt.com/role/DeferredIncomeTaxandincomeTaxExpenseScheduleofAnalysisofDeferredTaxAssetsandDeferredTaxLiabilitiesDetails Deferred Income Tax and income Tax Expense - Schedule of Analysis of Deferred Tax Assets and Deferred Tax Liabilities (Details) Details 174 false false R175.htm 9955635 - Disclosure - Deferred Income Tax and income Tax Expense - Schedule of Movement in Deferred Income Tax Assets and Liabilities (Details) Sheet http://www.kt.com/role/DeferredIncomeTaxandincomeTaxExpenseScheduleofMovementinDeferredIncomeTaxAssetsandLiabilitiesDetails Deferred Income Tax and income Tax Expense - Schedule of Movement in Deferred Income Tax Assets and Liabilities (Details) Details 175 false false R176.htm 9955636 - Disclosure - Deferred Income Tax and income Tax Expense - Schedule of Tax Impacts Recognized Directly To Equity (Details) Sheet http://www.kt.com/role/DeferredIncomeTaxandincomeTaxExpenseScheduleofTaxImpactsRecognizedDirectlyToEquityDetails Deferred Income Tax and income Tax Expense - Schedule of Tax Impacts Recognized Directly To Equity (Details) Details 176 false false R177.htm 9955637 - Disclosure - Deferred Income Tax and income Tax Expense - Schedule of Details of Income Tax Expense (Details) Sheet http://www.kt.com/role/DeferredIncomeTaxandincomeTaxExpenseScheduleofDetailsofIncomeTaxExpenseDetails Deferred Income Tax and income Tax Expense - Schedule of Details of Income Tax Expense (Details) Details 177 false false R178.htm 9955638 - Disclosure - Deferred Income Tax and income Tax Expense - Schedule of Tax on the Group's Profit Before Tax (Details) Sheet http://www.kt.com/role/DeferredIncomeTaxandincomeTaxExpenseScheduleofTaxontheGroupsProfitBeforeTaxDetails Deferred Income Tax and income Tax Expense - Schedule of Tax on the Group's Profit Before Tax (Details) Details 178 false false R179.htm 9955639 - Disclosure - Deferred Income Tax and income Tax Expense - Schedule of deferred tax assets and liabilities that are not recognized (Details) Sheet http://www.kt.com/role/DeferredIncomeTaxandincomeTaxExpenseScheduleofdeferredtaxassetsandliabilitiesthatarenotrecognizedDetails Deferred Income Tax and income Tax Expense - Schedule of deferred tax assets and liabilities that are not recognized (Details) Details 179 false false R180.htm 9955640 - Disclosure - Deferred Income Tax and income Tax Expense - Schedule of expected period of expiry for unused tax losses not recognized in deferred tax assets (Details) Sheet http://www.kt.com/role/DeferredIncomeTaxandincomeTaxExpenseScheduleofexpectedperiodofexpiryforunusedtaxlossesnotrecognizedindeferredtaxassetsDetails Deferred Income Tax and income Tax Expense - Schedule of expected period of expiry for unused tax losses not recognized in deferred tax assets (Details) Details 180 false false R181.htm 9955641 - Disclosure - Earnings per Share - Schedule of Basic and Diluted Earnings per Share from Operations (Details) Sheet http://www.kt.com/role/EarningsperShareScheduleofBasicandDilutedEarningsperSharefromOperationsDetails Earnings per Share - Schedule of Basic and Diluted Earnings per Share from Operations (Details) Details 181 false false R182.htm 9955642 - Disclosure - Earnings per Share - Schedule of Dilutive Potential Ordinary Shares (Details) Sheet http://www.kt.com/role/EarningsperShareScheduleofDilutivePotentialOrdinarySharesDetails Earnings per Share - Schedule of Dilutive Potential Ordinary Shares (Details) Details 182 false false R183.htm 9955643 - Disclosure - Dividend (Details) Sheet http://www.kt.com/role/DividendDetails Dividend (Details) Details http://www.kt.com/role/Dividend 183 false false R184.htm 9955644 - Disclosure - Cash Generated from Operations - Schedule of Cash Flows from Operating Activities (Details) Sheet http://www.kt.com/role/CashGeneratedfromOperationsScheduleofCashFlowsfromOperatingActivitiesDetails Cash Generated from Operations - Schedule of Cash Flows from Operating Activities (Details) Details 184 false false R185.htm 9955645 - Disclosure - Cash Generated from Operations - Schedule of Significant Transactions not Affecting Cash Flows (Details) Sheet http://www.kt.com/role/CashGeneratedfromOperationsScheduleofSignificantTransactionsnotAffectingCashFlowsDetails Cash Generated from Operations - Schedule of Significant Transactions not Affecting Cash Flows (Details) Details 185 false false R186.htm 9955646 - Disclosure - Changes in Liabilities Arising from Financing Activities - Schedule of Changes in Liabilities Arising from Financial Activities (Details) Sheet http://www.kt.com/role/ChangesinLiabilitiesArisingfromFinancingActivitiesScheduleofChangesinLiabilitiesArisingfromFinancialActivitiesDetails Changes in Liabilities Arising from Financing Activities - Schedule of Changes in Liabilities Arising from Financial Activities (Details) Details 186 false false R187.htm 9955647 - Disclosure - Segment Information - Schedule of Segment Information (Details) Sheet http://www.kt.com/role/SegmentInformationScheduleofSegmentInformationDetails Segment Information - Schedule of Segment Information (Details) Details 187 false false R188.htm 9955648 - Disclosure - Segment Information - Schedule of Operating Revenues and Non Current Assets by Geographical Regions (Details) Sheet http://www.kt.com/role/SegmentInformationScheduleofOperatingRevenuesandNonCurrentAssetsbyGeographicalRegionsDetails Segment Information - Schedule of Operating Revenues and Non Current Assets by Geographical Regions (Details) Details 188 false false R189.htm 9955649 - Disclosure - Related Party Transactions - Schedule of Related Parties Outstanding Balances of Receivables and Payables (Details) Sheet http://www.kt.com/role/RelatedPartyTransactionsScheduleofRelatedPartiesOutstandingBalancesofReceivablesandPayablesDetails Related Party Transactions - Schedule of Related Parties Outstanding Balances of Receivables and Payables (Details) Details 189 false false R190.htm 9955650 - Disclosure - Related Party Transactions - Schedule of Significant Transactions with Related Parties (Details) Sheet http://www.kt.com/role/RelatedPartyTransactionsScheduleofSignificantTransactionswithRelatedPartiesDetails Related Party Transactions - Schedule of Significant Transactions with Related Parties (Details) Details 190 false false R191.htm 9955651 - Disclosure - Related Party Transactions - Schedule of Significant Transactions with Related Parties (Details) Sheet http://www.kt.com/role/RelatedPartyTransactionsScheduleofSignificantTransactionswithRelatedPartiesDetails_1 Related Party Transactions - Schedule of Significant Transactions with Related Parties (Details) Details 191 false false R192.htm 9955652 - Disclosure - Related Party Transactions - Schedule of Key Management Compensation (Details) Sheet http://www.kt.com/role/RelatedPartyTransactionsScheduleofKeyManagementCompensationDetails Related Party Transactions - Schedule of Key Management Compensation (Details) Details 192 false false R193.htm 9955653 - Disclosure - Related Party Transactions - Schedule of Fund Transactions with Related Parties (Details) Sheet http://www.kt.com/role/RelatedPartyTransactionsScheduleofFundTransactionswithRelatedPartiesDetails Related Party Transactions - Schedule of Fund Transactions with Related Parties (Details) Details 193 false false R194.htm 9955654 - Disclosure - Related Party Transactions - Additional Information (Details) Sheet http://www.kt.com/role/RelatedPartyTransactionsAdditionalInformationDetails Related Party Transactions - Additional Information (Details) Details 194 false false R195.htm 9955655 - Disclosure - Financial Risk Management - Schedule of Exposures to Risks, Effects on Profit before Income Tax and Shareholders' Equity (Details) Sheet http://www.kt.com/role/FinancialRiskManagementScheduleofExposurestoRisksEffectsonProfitbeforeIncomeTaxandShareholdersEquityDetails Financial Risk Management - Schedule of Exposures to Risks, Effects on Profit before Income Tax and Shareholders' Equity (Details) Details 195 false false R196.htm 9955656 - Disclosure - Financial Risk Management - Schedule of Details of Financial Assets and Liabilities in Foreign Currencies (Details) Sheet http://www.kt.com/role/FinancialRiskManagementScheduleofDetailsofFinancialAssetsandLiabilitiesinForeignCurrenciesDetails Financial Risk Management - Schedule of Details of Financial Assets and Liabilities in Foreign Currencies (Details) Details 196 false false R197.htm 9955657 - Disclosure - Financial Risk Management - Schedule of Maximum Exposure to Credit Risk (Details) Sheet http://www.kt.com/role/FinancialRiskManagementScheduleofMaximumExposuretoCreditRiskDetails Financial Risk Management - Schedule of Maximum Exposure to Credit Risk (Details) Details 197 false false R198.htm 9955658 - Disclosure - Financial Risk Management - Additional Information (Details) Sheet http://www.kt.com/role/FinancialRiskManagementAdditionalInformationDetails Financial Risk Management - Additional Information (Details) Details 198 false false R199.htm 9955659 - Disclosure - Financial Risk Management - Schedule of Expected Credit Losses Reflect Forward-Looking Information (Details) Sheet http://www.kt.com/role/FinancialRiskManagementScheduleofExpectedCreditLossesReflectForwardLookingInformationDetails Financial Risk Management - Schedule of Expected Credit Losses Reflect Forward-Looking Information (Details) Details 199 false false R200.htm 9955660 - Disclosure - Financial Risk Management - Schedule of Details of Changes in Provisions for Impairment of Trade Receivables and Other Financial Assets at Amortized Costs (Details) Sheet http://www.kt.com/role/FinancialRiskManagementScheduleofDetailsofChangesinProvisionsforImpairmentofTradeReceivablesandOtherFinancialAssetsatAmortizedCostsDetails Financial Risk Management - Schedule of Details of Changes in Provisions for Impairment of Trade Receivables and Other Financial Assets at Amortized Costs (Details) Details 200 false false R201.htm 9955661 - Disclosure - Financial Risk Management - Schedule of Impairment of Trade Receivable (Details) Sheet http://www.kt.com/role/FinancialRiskManagementScheduleofImpairmentofTradeReceivableDetails Financial Risk Management - Schedule of Impairment of Trade Receivable (Details) Details 201 false false R202.htm 9955662 - Disclosure - Financial Risk Management -Schedule of Contractual Undiscounted Cash Flows (Details) Sheet http://www.kt.com/role/FinancialRiskManagementScheduleofContractualUndiscountedCashFlowsDetails Financial Risk Management -Schedule of Contractual Undiscounted Cash Flows (Details) Details 202 false false R203.htm 9955663 - Disclosure - Financial Risk Management - Schedule of Cash Outflow and Inflow of Derivatives Settled Gross or Net are Undiscounted Contractual Cash Flow (Details) Sheet http://www.kt.com/role/FinancialRiskManagementScheduleofCashOutflowandInflowofDerivativesSettledGrossorNetareUndiscountedContractualCashFlowDetails Financial Risk Management - Schedule of Cash Outflow and Inflow of Derivatives Settled Gross or Net are Undiscounted Contractual Cash Flow (Details) Details 203 false false R204.htm 9955664 - Disclosure - Financial Risk Management - Schedule of Debt-to-equity Ratios (Details) Sheet http://www.kt.com/role/FinancialRiskManagementScheduleofDebttoequityRatiosDetails Financial Risk Management - Schedule of Debt-to-equity Ratios (Details) Details 204 false false R205.htm 9955665 - Disclosure - Financial Risk Management - Schedule of Gearing Ratios (Details) Sheet http://www.kt.com/role/FinancialRiskManagementScheduleofGearingRatiosDetails Financial Risk Management - Schedule of Gearing Ratios (Details) Details 205 false false R206.htm 9955666 - Disclosure - Financial Risk Management - Schedule of Group's Recognized Financial Assets Subject to Enforceable Master Netting Arrangements or Similar Agreements (Details) Sheet http://www.kt.com/role/FinancialRiskManagementScheduleofGroupsRecognizedFinancialAssetsSubjecttoEnforceableMasterNettingArrangementsorSimilarAgreementsDetails Financial Risk Management - Schedule of Group's Recognized Financial Assets Subject to Enforceable Master Netting Arrangements or Similar Agreements (Details) Details 206 false false R207.htm 9955667 - Disclosure - Financial Risk Management - Schedule of Group's Recognized Financial Liabilities Subject to Enforceable Master Netting Arrangements or Similar Agreements (Details) Sheet http://www.kt.com/role/FinancialRiskManagementScheduleofGroupsRecognizedFinancialLiabilitiesSubjecttoEnforceableMasterNettingArrangementsorSimilarAgreementsDetails Financial Risk Management - Schedule of Group's Recognized Financial Liabilities Subject to Enforceable Master Netting Arrangements or Similar Agreements (Details) Details 207 false false R208.htm 9955668 - Disclosure - Fair Value -Schedule of Carrying Amount and Fair Value of Financial Instruments by Category (Details) Sheet http://www.kt.com/role/FairValueScheduleofCarryingAmountandFairValueofFinancialInstrumentsbyCategoryDetails Fair Value -Schedule of Carrying Amount and Fair Value of Financial Instruments by Category (Details) Details 208 false false R209.htm 9955669 - Disclosure - Fair Value - Schedule of Fair Value Non of Financial Instruments (Details) Sheet http://www.kt.com/role/FairValueScheduleofFairValueNonofFinancialInstrumentsDetails Fair Value - Schedule of Fair Value Non of Financial Instruments (Details) Details 209 false false R210.htm 9955670 - Disclosure - Fair Value - Schedule of Changes in Level 3 of Fair Value Hierarchy for Recurring Fair Value Measurements (Details) Sheet http://www.kt.com/role/FairValueScheduleofChangesinLevel3ofFairValueHierarchyforRecurringFairValueMeasurementsDetails Fair Value - Schedule of Changes in Level 3 of Fair Value Hierarchy for Recurring Fair Value Measurements (Details) Details 210 false false R211.htm 9955671 - Disclosure - Fair Value -Schedule of Valuation Techniques and Inputs (Details) Sheet http://www.kt.com/role/FairValueScheduleofValuationTechniquesandInputsDetails Fair Value -Schedule of Valuation Techniques and Inputs (Details) Details 211 false false R212.htm 9955672 - Disclosure - Interests in Unconsolidated Structured Entities - Schedule of Unconsolidated Structured Entities and Nature of Risks (Details) Sheet http://www.kt.com/role/InterestsinUnconsolidatedStructuredEntitiesScheduleofUnconsolidatedStructuredEntitiesandNatureofRisksDetails Interests in Unconsolidated Structured Entities - Schedule of Unconsolidated Structured Entities and Nature of Risks (Details) Details 212 false false R213.htm 9955673 - Disclosure - Information About Non-controlling Interests - Schedule of Changes in Accumulated Non-controlling Interests (Details) Sheet http://www.kt.com/role/InformationAboutNoncontrollingInterestsScheduleofChangesinAccumulatedNoncontrollingInterestsDetails Information About Non-controlling Interests - Schedule of Changes in Accumulated Non-controlling Interests (Details) Details 213 false false R214.htm 9955674 - Disclosure - Information About Non-controlling Interests - Schedule of Financial Information on Subsidiaries (Details) Sheet http://www.kt.com/role/InformationAboutNoncontrollingInterestsScheduleofFinancialInformationonSubsidiariesDetails Information About Non-controlling Interests - Schedule of Financial Information on Subsidiaries (Details) Details 214 false false R215.htm 9955675 - Disclosure - Information About Non-controlling Interests - Schedule of Consolidated Statements of Comprehensive Income (Details) Sheet http://www.kt.com/role/InformationAboutNoncontrollingInterestsScheduleofConsolidatedStatementsofComprehensiveIncomeDetails Information About Non-controlling Interests - Schedule of Consolidated Statements of Comprehensive Income (Details) Details 215 false false R216.htm 9955676 - Disclosure - Information About Non-controlling Interests - Schedule of Consolidated Statements of Cash Flows (Details) Sheet http://www.kt.com/role/InformationAboutNoncontrollingInterestsScheduleofConsolidatedStatementsofCashFlowsDetails Information About Non-controlling Interests - Schedule of Consolidated Statements of Cash Flows (Details) Details 216 false false R217.htm 9955677 - Disclosure - Information About Non-controlling Interests - Summary of Changes in Ownership Interest on the Equity Attributable to Owners (Details) Sheet http://www.kt.com/role/InformationAboutNoncontrollingInterestsSummaryofChangesinOwnershipInterestontheEquityAttributabletoOwnersDetails Information About Non-controlling Interests - Summary of Changes in Ownership Interest on the Equity Attributable to Owners (Details) Details 217 false false R218.htm 9955678 - Disclosure - Events After the Reporting Period - Additional Information (Details) Sheet http://www.kt.com/role/EventsAftertheReportingPeriodAdditionalInformationDetails Events After the Reporting Period - Additional Information (Details) Details 218 false false R219.htm 9955679 - Disclosure - Events After the Reporting Period - Schedule of Public Bonds Issued After Reporting Period (Details) Sheet http://www.kt.com/role/EventsAftertheReportingPeriodScheduleofPublicBondsIssuedAfterReportingPeriodDetails Events After the Reporting Period - Schedule of Public Bonds Issued After Reporting Period (Details) Details 219 false false All Reports Book All Reports kt-20251231.htm kt-20251231.xsd kt-20251231_cal.xml kt-20251231_def.xml kt-20251231_lab.xml kt-20251231_pre.xml http://xbrl.sec.gov/cyd/2025 http://xbrl.sec.gov/dei/2025 http://xbrl.sec.gov/ecd/2025 https://xbrl.ifrs.org/taxonomy/2025-03-27/ifrs-full true true