XML 109 R97.htm IDEA: XBRL DOCUMENT
v3.19.1

Financial Instruments by Category - Summary of Gains or Losses Arising From Financial Instruments by Category (Detail) - KRW (₩) ₩ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Disclosure of detailed information about financial instruments [line items] |  |  |
Interest income | ₩ 244,796 | ₩ 93,078 | ₩ 115,686
Interest expense | (296,874) | (302,464) | (337,219)
Dividend income | 11,146 | 6,212 |
Total | (116,643) | (150,420) | (308,677)
Other comprehensive income for the year | (54,628) | (68,288) | (5,670)
Reclassified to profit or loss from other comprehensive income for the year | (44,279) | 86,479 |
Financial liabilities designated as at fair value through profit or loss [member] |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |
Gain (loss) on disposal |  |  | (632)
Gain (loss) on valuation | (2,708) | (3,078) | 33
Derivatives used for hedging [member] |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |
Gain (loss) on transaction | 20,678 |  | 8,329
Gain (loss) on valuation | 42,195 | (145,885) | (138)
Other comprehensive income for the year | (2,810) | (66,624) | 4,295
Reclassified to profit or loss from other comprehensive income for the year | (28,388) | 91,698 | (3,956)
Financial liabilities at amortized cost [member] |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |
Interest expense | (296,894) | (302,464) | (337,219)
Gain(loss) on repayment | (15) |  |
Gain (loss) foreign currency transaction | (30,956) | 62,347 | (7,518)
Gain(loss) foreign currency translation | (66,050) | 225,695 | (112,864)
Financial assets at amortized cost [member] |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |
Interest income | 93,233 | 108,608 | 129,813
Gain (loss) foreign currency transaction | 19,396 | (11,949) | (7,493)
Gain (loss) on foreign currency translation | (2,901) | (12,354) | 3,083
Gain (loss) on disposal | 44 | (20,351) | (15,838)
Gain (loss) on valuation | (110,544) | (44,219) | (92,589)
Financial assets at fair value through profit or loss [member] |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |
Interest income | 9,194 |  |
Dividend income | 1,207 |  |
Gain (loss) on disposal | 1,713 |  |
Gain (loss) on valuation | 10,768 |  |
Financial assets at fair value through other comprehensive income [member] |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |
Interest income | 163,390 |  |
Dividend income | 1,704 |  |
Gain (loss) on disposal | (13,818) |  |
Impairment loss | (2,416) |  |
Other comprehensive income for the year | 43,811 |  |
Asset at fair value through profit or loss [member] |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |
Dividend income |  | 1 |
Gain (loss) on disposal |  | 153 | 186
Gain (loss) on valuation |  | (464) | (7,184)
Derivative financial liabilities [member] |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |
Gain (loss) on transaction | 7,272 | (58,569) |
Gain (loss) on valuation | 22,065 | (63,640) | 109,436
Other comprehensive income for the year | 20,078 | (44,429) | 60,501
Reclassified to profit or loss from other comprehensive income for the year | ₩ (15,891) | 50,231 | (71,915)
Available-for-sale [member] |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |
Interest income |  | 453 | 40
Dividend income |  | 5,174 | 3,926
Gain (loss) on disposal |  | 89,598 | 22,695
Impairment loss |  | (6,137) | (966)
Other comprehensive income for the year |  | 51,235 | 10,925
Reclassified to profit or loss from other comprehensive income for the year |  | ₩ (55,450) | (3,840)
Held-to-maturity financial assets [member] |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |
Interest income |  |  | ₩ 213

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

X
- Definition The amount recognised as a reduction of the carrying amount of an asset or cash-generating unit to its recoverable amount. [Refer: Carrying amount [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 36 -IssueDate 2018-01-01 -Paragraph 130 -Subparagraph b -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=36&date=2018-03-01&anchor=para_130_b&doctype=Standard -URIDate 2018-03-16 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 36 -IssueDate 2018-01-01 -Paragraph 130 -Subparagraph d -Clause ii -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=36&date=2018-03-01&anchor=para_130_d_ii&doctype=Standard -URIDate 2018-03-16 + Details
Name: | ifrs-full_ImpairmentLoss
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The amount of expense arising from interest. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 8 -IssueDate 2018-01-01 -Paragraph 23 -Subparagraph d -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=8&date=2018-03-01&anchor=para_23_d&doctype=Standard -URIDate 2018-03-16 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 8 -IssueDate 2018-01-01 -Paragraph 28 -Subparagraph e -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=8&date=2018-03-01&anchor=para_28_e&doctype=Standard -URIDate 2018-03-16 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 12 -IssueDate 2018-01-01 -Paragraph B13 -Subparagraph f -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=12&date=2018-03-01&anchor=para_B13_f&doctype=Appendix&seq=2 -URIDate 2018-03-16 + Details
Name: | ifrs-full_InterestExpense
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The amount of income and expense (including reclassification adjustments) that is not recognised in profit or loss as required or permitted by IFRSs. [Refer: IFRSs [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2018-01-01 -Paragraph 106 -Subparagraph d -Clause ii -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_106_d_ii&doctype=Standard -URIDate 2018-03-16 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 12 -IssueDate 2018-01-01 -Paragraph B12 -Subparagraph b -Clause viii -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=12&date=2018-03-01&anchor=para_B12_b_viii&doctype=Appendix&seq=2 -URIDate 2018-03-16 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2018-01-01 -Paragraph 81A -Subparagraph b -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_81A_b&doctype=Standard -URIDate 2018-03-16 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2018-01-01 -Paragraph 91 -Subparagraph a -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_91_a&doctype=Standard -URIDate 2018-03-16 + Details
Name: | ifrs-full_OtherComprehensiveIncome
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The amount of other comprehensive income that will be reclassified to profit or loss, before tax. [Refer: Other comprehensive income] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 1 -IssueDate 2018-01-01 -Paragraph IG6 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_IG6&doctype=Implementation%20Guidance -URIDate 2018-03-16 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 1 -IssueDate 2018-01-01 -Paragraph 82A -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_82A&doctype=Standard -URIDate 2018-03-16 + Details
Name: | ifrs-full_OtherComprehensiveIncomeThatWillBeReclassifiedToProfitOrLossBeforeTax
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The amount of dividends recognised as income. Dividends are distributions of profits to holders of equity investments in proportion to their holdings of a particular class of capital. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 1 -IssueDate 2018-01-01 -Paragraph 112 -Subparagraph c -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_112_c&doctype=Standard -URIDate 2018-03-16 + Details
Name: | ifrs-full_RevenueFromDividends
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The amount of income arising from interest. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 8 -IssueDate 2018-01-01 -Paragraph 23 -Subparagraph c -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=8&date=2018-03-01&anchor=para_23_c&doctype=Standard -URIDate 2018-03-16 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 8 -IssueDate 2018-01-01 -Paragraph 28 -Subparagraph e -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=8&date=2018-03-01&anchor=para_28_e&doctype=Standard -URIDate 2018-03-16 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 12 -IssueDate 2018-01-01 -Paragraph B13 -Subparagraph e -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=12&date=2018-03-01&anchor=para_B13_e&doctype=Appendix&seq=2 -URIDate 2018-03-16 Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 1 -IssueDate 2018-01-01 -Paragraph 112 -Subparagraph c -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_112_c&doctype=Standard -URIDate 2018-03-16 + Details
Name: | ifrs-full_RevenueFromInterest
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Gain loss on derivatives transactions. + References No definition available. + Details
Name: | kt_GainLossOnDerivativesTransactions
Namespace Prefix: | kt_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Gain Loss On Foreign Currency Transaction + References No definition available. + Details
Name: | kt_GainLossOnForeignCurrencyTransaction
Namespace Prefix: | kt_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Gain Loss on foreign currency translations. + References No definition available. + Details
Name: | kt_GainLossOnForeignCurrencyTranslations
Namespace Prefix: | kt_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Gain (loss) on repayment. + References No definition available. + Details
Name: | kt_GainLossOnRepayment
Namespace Prefix: | kt_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Gain loss on valuation. + References No definition available. + Details
Name: | kt_GainLossOnValuation
Namespace Prefix: | kt_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Gain on foreign currency translations. + References No definition available. + Details
Name: | kt_GainOnForeignCurrencyTranslations
Namespace Prefix: | kt_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Gains Losses Arising From Financial Instruments By Category + References No definition available. + Details
Name: | kt_GainsLossesArisingFromFinancialInstrumentsByCategory
Namespace Prefix: | kt_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Gains (losses) on disposal. + References No definition available. + Details
Name: | kt_GainsLossesOnDisposal
Namespace Prefix: | kt_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | ifrs-full_CategoriesOfFinancialLiabilitiesAxis=ifrs-full_FinancialLiabilitiesAtFairValueThroughProfitOrLossCategoryMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_CategoriesOfFinancialLiabilitiesAxis=kt_DerivativesLiabilitiesUsedForHedgingMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_CategoriesOfFinancialLiabilitiesAxis=ifrs-full_FinancialLiabilitiesAtAmortisedCostCategoryMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_CategoriesOfFinancialAssetsAxis=ifrs-full_FinancialAssetsAtAmortisedCostCategoryMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_CategoriesOfFinancialAssetsAxis=ifrs-full_FinancialAssetsAtFairValueThroughProfitOrLossCategoryMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_CategoriesOfFinancialAssetsAxis=ifrs-full_FinancialAssetsAtFairValueThroughOtherComprehensiveIncomeCategoryMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_CategoriesOfFinancialAssetsAxis=kt_AssetAtFairValueThroughProfitOrLossMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_CategoriesOfFinancialAssetsAxis=kt_DerivativeFinancialLiabilitiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_CategoriesOfFinancialAssetsAxis=ifrs-full_FinancialAssetsAvailableforsaleCategoryMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_CategoriesOfFinancialAssetsAxis=ifrs-full_HeldtomaturityInvestmentsCategoryMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |