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Financial Instruments by Category - Summary of Gains or Losses Arising From Financial Instruments by Category (Parenthetical) (Detail) - KRW (₩) ₩ in Millions | 12 Months Ended
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Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Disclosure of detailed information about financial instruments [line items] |  |  |
Interest income recognized as operating revenue | ₩ 273,460 | ₩ 270,571 | ₩ 282,704
Interest expense recognized as operating expense | 263,389 | 263,579 | 278,427
Profit and loss from foreign currency transaction | 19,976 | 17,493 | 24,596
BC Card Co., Ltd. [member] |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |
Interest income recognized as operating revenue | 27,440 | 20,854 | 21,018
Interest expense recognized as operating expense | 5,458 | 1,456 | 548
Profit and loss from foreign currency transaction | 2,373 | 19,687 | 17,006
Operating expenses from foreign currency translation | 3 | 56 | 5
Dividend income | 1,340 | 2,059 | 2,250
Gain (loss) on valuation | ₩ 15,459 | ₩ 40,822 | ₩ 15,429

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