XML 220 R208.htm IDEA: XBRL DOCUMENT
v3.21.1

Financial Risk Management - Summary of Exposures to Risks, Effects on Profit before Income Tax and Shareholders' Equity (Detail) - KRW (₩) ₩ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
10% strengthening in foreign exchange rate [member] |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |
Fluctuation of foreign exchange rate | 10.00% | 10.00% | 10.00%
Income before tax | ₩ 25,220 | ₩ 45,149 | ₩ 7,212
Shareholders' equity | ₩ 36,961 | ₩ 52,092 | ₩ 10,196
10% weakening in foreign exchange rate [member] |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |
Fluctuation of foreign exchange rate | 10.00% | 10.00% | 10.00%
Income before tax | ₩ (25,220) | ₩ (45,149) | ₩ (12,413)
Shareholders' equity | ₩ (36,961) | ₩ (52,092) | ₩ (9,625)
Ten percentage increase in market equity price [member] |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |
Fluctuation of price | 10.00% | 10.00% | 10.00%
Income before tax | ₩ 2,811 | ₩ 24 | ₩ 12
Shareholders' equity | ₩ 3,472 | ₩ 613 | ₩ 898
10% decrease in market equity price [member] |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |
Fluctuation of price | 10.00% | 10.00% | 10.00%
Income before tax | ₩ (2,811) | ₩ (24) | ₩ (12)
Shareholders' equity | ₩ (3,472) | ₩ (613) | ₩ (898)
100 basis point increase in market interest rate [Member] |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |
Fluctuation of interest rate | 1.00% | 1.00% | 1.00%
Income before tax | ₩ 973 | ₩ 425 | ₩ 1,059
Shareholders' equity | ₩ 18,584 | ₩ 14,764 | ₩ 9,689
100 basis point decrease in market interest rate [Member] |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |
Fluctuation of interest rate | 1.00% | 1.00% | 1.00%
Income before tax | ₩ (973) | ₩ (482) | ₩ (1,958)
Shareholders' equity | ₩ (19,377) | ₩ (19,280) | ₩ (10,237)

X
- Definition The increase (decrease) in equity. [Refer: Equity] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2020-01-01 -Paragraph 106 -Subparagraph d -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2020-en-r&anchor=para_106_d&doctype=Standard -URIDate 2020-01-01 + Details
Name: | ifrs-full_ChangesInEquity
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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 Foreign exchange rate volatility. + References No definition available. + Details
Name: | kt_ForeignExchangeRateVolatility
Namespace Prefix: | kt_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Increase (decrease) in income before tax. + References No definition available. + Details
Name: | kt_IncreaseDecreaseInIncomeBeforeTax
Namespace Prefix: | kt_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Percentage of reasonably possible increase decrease in interest rate. + References No definition available. + Details
Name: | kt_PercentageOfReasonablyPossibleIncreaseDecreaseInInterestRate
Namespace Prefix: | kt_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of reasonably possible increase decrease in market price. + References No definition available. + Details
Name: | kt_PercentageOfReasonablyPossibleIncreaseDecreaseInMarketPrice
Namespace Prefix: | kt_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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

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

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

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

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

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