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Commitments and Contingencies - Summary of Guarantees Provided by the Group for Third Parties (Detail) ₩ in Millions | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2020 KRW (₩) | Dec. 31, 2020 SGD ($) | Dec. 31, 2020 USD ($) | Dec. 31, 2019 KRW (₩)
Disclosure of detailed information about borrowings [line items] |  |  |  |
Used amount | ₩ 7,316,298 | $ 284,000,000 | $ 519,598,989 | ₩ 7,298,867
Maturity | Jun. 5, 2025 |  |  |
KT Engineering Co Ltd KT ENGCORE Co Ltd [Member] | Shinhan Bank [member] | Guarantees [member] |  |  |  |
Disclosure of detailed information about borrowings [line items] |  |  |  |
Subject to payment guarantees | Gasan Solar Power Plant Inc. |  |  |
Limit | ₩ 4,700 |  |  |
Used amount | ₩ 1,371 |  |  |
Maturity | Jan. 08, 2025 |  |  |
KT Engineering Co Ltd KT ENGCORE Co Ltd [Member] | Suhyup Bank [Member] | Guarantees [member] |  |  |  |
Disclosure of detailed information about borrowings [line items] |  |  |  |
Subject to payment guarantees | SPP Inc. |  |  |
Limit | ₩ 3,250 |  |  |
Used amount | ₩ 932 |  |  |
Maturity | Feb. 16, 2024 |  |  |
KT Engineering Co Ltd KT ENGCORE Co Ltd [Member] | Suhyup Bank One [Member] | Guarantees [member] |  |  |  |
Disclosure of detailed information about borrowings [line items] |  |  |  |
Subject to payment guarantees | Korea Cell Inc. |  |  |
Limit | ₩ 3,250 |  |  |
Used amount | ₩ 880 |  |  |
Maturity | Feb. 16, 2024 |  |  |
KT Engineering Co Ltd KT ENGCORE Co Ltd [Member] | Suhyup Bank Two [Member] | Guarantees [member] |  |  |  |
Disclosure of detailed information about borrowings [line items] |  |  |  |
Subject to payment guarantees | San-Ya Agricultural Association Corporation |  |  |
Limit | ₩ 3,250 |  |  |
Used amount | ₩ 888 |  |  |
Maturity | Feb. 16, 2024 |  |  |
KT Engineering Co Ltd KT ENGCORE Co Ltd [Member] | NH Investment Securities CoLtd [Member] | Guarantees [member] |  |  |  |
Disclosure of detailed information about borrowings [line items] |  |  |  |
Subject to payment guarantees | Ciocanesti Korea Co., Ltd. |  |  |
Limit | ₩ 7,600 |  |  |
Used amount | ₩ 7,600 |  |  |
Maturity | Jun. 8, 2017 |  |  |
KT Hitel Co., Ltd. [member] | Cash payers [member] | Guarantees [member] |  |  |  |
Disclosure of detailed information about borrowings [line items] |  |  |  |
Subject to payment guarantees | Shinhan Bank |  |  |
Limit | ₩ 700 |  |  |
Nasmedia Co Ltd [member] | Korea Securities Finance Corp [Member] | Guarantees [member] |  |  |  |
Disclosure of detailed information about borrowings [line items] |  |  |  |
Subject to payment guarantees | Stockholders Association Members |  |  |
Limit | ₩ 5,654 |  |  |
Used amount | ₩ 2,735 |  |  |
Bottom of range [member] | KT Hitel Co., Ltd. [member] | Cash payers [member] | Guarantees [member] |  |  |  |
Disclosure of detailed information about borrowings [line items] |  |  |  |
Maturity | Apr. 17, 2020 |  |  |
Top of range [member] | KT Hitel Co., Ltd. [member] | Cash payers [member] | Guarantees [member] |  |  |  |
Disclosure of detailed information about borrowings [line items] |  |  |  |
Maturity | Apr. 16, 2021 |  |  |

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