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Financial Risk Management - Summary of Debt-to-equity Ratios (Detail) - KRW (₩) ₩ in Millions | 12 Months Ended |  |
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Disclosure of detailed information about financial instruments [abstract] |  |  |  |
Total liabilities | ₩ 18,111,112 | ₩ 19,491,530 |  |
Total equity | ₩ 15,551,433 | ₩ 15,140,684 | ₩ 14,658,490 | ₩ 13,183,354
Debt-to-equity ratio | 116.00% | 129.00% |  |

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