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Other Financial Assets and Liabilities - Summary of Other Financial Assets and Liabilities (Parenthetical) (Detail) - KRW (₩) ₩ in Millions | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019
Disclosure of detailed information about financial instruments [line items] |  |
Other financial assets | ₩ 1,747,187 | ₩ 1,690,046
Korea software financial cooperative [member] |  |
Disclosure of detailed information about financial instruments [line items] |  |
Available-for-sale financial assets investment amount | 5,491 | 1,849
Ustream Inc. [member] |  |
Disclosure of detailed information about financial instruments [line items] |  |
Proceeds from the disposal of Subsidiary | 104,442 | 91,445
Money Market Wrap and Money Market Trust [member] |  |
Disclosure of detailed information about financial instruments [line items] |  |
Other financial assets | ₩ 509,068 | ₩ 406,062

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