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Financial Risk Management - Summary of Cash Outflow and Inflow of Derivatives Settled Gross or Net are Undiscounted Contractual Cash Flow (Detail) - KRW (₩) ₩ in Millions | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
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Disclosure of maturity analysis for derivative financial liabilities [Line Items] |  |  |
Outflow | ₩ 2,760,957 | ₩ 2,439,559 | ₩ 1,711,595
Inflow | 2,857,949 | 2,496,356 | 1,686,804
Less than 1 year [member] |  |  |
Disclosure of maturity analysis for derivative financial liabilities [Line Items] |  |  |
Outflow | 650,497 | 455,343 | 638,171
Inflow | 684,720 | 484,505 | 608,270
1-5 years [member] |  |  |
Disclosure of maturity analysis for derivative financial liabilities [Line Items] |  |  |
Outflow | 1,602,513 | 1,466,915 | 546,791
Inflow | 1,648,746 | 1,492,718 | 568,976
More than 5 years [member] |  |  |
Disclosure of maturity analysis for derivative financial liabilities [Line Items] |  |  |
Outflow | 507,947 | 517,301 | 526,633
Inflow | ₩ 524,483 | ₩ 519,133 | ₩ 509,558

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