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Deferred Income Tax and Income Tax Expense - Summary of deferred tax assets and liabilities that are not recognized (Detail) - KRW (₩) ₩ in Millions | Dec. 31, 2020 | Dec. 31, 2019
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Disclosure of temporary difference, unused tax losses and unused tax credits [line items] |  |
Deductible Temporary Differences For Which No Deferred Tax Asset and Liabiities Is Recognised | ₩ 679,419 | ₩ 674,102
Taxable Temporary Differences For Which No Deferred Tax Asset and Liabilities Is Recognised | 142,416 | 152,036
Investment in subsidiaries, associates, and joint ventures |  |
Disclosure of temporary difference, unused tax losses and unused tax credits [line items] |  |
Deductible Temporary Differences For Which No Deferred Tax Asset and Liabiities Is Recognised | 583,890 | 610,351
Taxable Temporary Differences For Which No Deferred Tax Asset and Liabilities Is Recognised | 132,848 | 141,664
Unused tax loss |  |
Disclosure of temporary difference, unused tax losses and unused tax credits [line items] |  |
Deductible Temporary Differences For Which No Deferred Tax Asset and Liabiities Is Recognised | 28,115 | 31,257
Unused Tax credit |  |
Disclosure of temporary difference, unused tax losses and unused tax credits [line items] |  |
Deductible Temporary Differences For Which No Deferred Tax Asset and Liabiities Is Recognised | 2,654 |
Others |  |
Disclosure of temporary difference, unused tax losses and unused tax credits [line items] |  |
Deductible Temporary Differences For Which No Deferred Tax Asset and Liabiities Is Recognised | 64,760 | 32,494
Others |  |
Disclosure of temporary difference, unused tax losses and unused tax credits [line items] |  |
Taxable Temporary Differences For Which No Deferred Tax Asset and Liabilities Is Recognised | ₩ 9,568 | ₩ 10,372

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