XML 237 R104.htm IDEA: XBRL DOCUMENT
v3.20.1

Other Financial Assets and Liabilities - Summary of Valuation Gains and Losses on Derivatives Contracts (Detail) - KRW (₩) ₩ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Disclosure of detailed information about financial instruments [line items] |  |  |
Valuation gain | ₩ 77,275 | ₩ 66,305 | ₩ 57
Valuation loss | 15,829 | 2,045 | 209,582
Other comprehensive income | 91,521 | 21,651 | (146,508)
Interest rate swap [member] |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |
Valuation gain |  | 192 | 38
Valuation loss | 45 |  |
Other comprehensive income | (963) | (488) | 637
Currency swap [member] |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |
Valuation gain | 72,417 | 58,912 | 19
Valuation loss | 15,784 | 2,045 | 187,468
Other comprehensive income | 87,626 | 22,139 | (146,752)
Currency forwards [member] |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |
Valuation gain | 4,858 | ₩ 7,201 |
Valuation loss |  |  | 22,114
Other comprehensive income | ₩ 4,858 |  | ₩ (393)

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 gains (losses) recognised in other comprehensive income on cash flow hedges, before tax. [Refer: Cash flow hedges [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2019-01-01 -Paragraph 91 -Subparagraph b -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2019-en-r&anchor=para_91_b&doctype=Standard -URIDate 2019-03-27 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Note Expiry date 2021-01-01 -Name IFRS -Number 7 -IssueDate 2019-01-01 -Paragraph 23 -Subparagraph c -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2017-en-b&anchor=para_23_c&doctype=Standard&book=b -URIDate 2019-03-27 + Details
Name: | ifrs-full_GainsLossesOnCashFlowHedgesBeforeTax
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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

X
- Definition Loss on valuation of derivatives. + References No definition available. + Details
Name: | kt_LossOnValuationOfDerivatives
Namespace Prefix: | kt_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | ifrs-full_ClassesOfFinancialInstrumentsAxis=ifrs-full_InterestRateSwapContractMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_ClassesOfFinancialInstrumentsAxis=ifrs-full_CurrencySwapContractMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_ClassesOfFinancialInstrumentsAxis=ifrs-full_ForwardContractMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |