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Inventories - Summary of Inventories Net (Detail) - KRW (₩) ₩ in Millions | Dec. 31, 2020 | Dec. 31, 2019
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Disclosure of inventories [line items] |  |
Inventories | ₩ 534,636 | ₩ 791,677
Merchandise [member] |  |
Disclosure of inventories [line items] |  |
Inventories | 517,632 | 661,253
Others [member] |  |
Disclosure of inventories [line items] |  |
Inventories | 17,004 | 130,424
Gross carrying amount [member] |  |
Disclosure of inventories [line items] |  |
Inventories | 667,860 | 936,115
Gross carrying amount [member] | Merchandise [member] |  |
Disclosure of inventories [line items] |  |
Inventories | 650,856 | 805,691
Gross carrying amount [member] | Others [member] |  |
Disclosure of inventories [line items] |  |
Inventories | 17,004 | 130,424
Valuation allowance [member] |  |
Disclosure of inventories [line items] |  |
Inventories | (133,224) | (144,438)
Valuation allowance [member] | Merchandise [member] |  |
Disclosure of inventories [line items] |  |
Inventories | ₩ (133,224) | ₩ (144,438)

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