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Fair Value - Summary of Changes in Level 3 of Fair Value Hierarchy for Recurring Fair Value Measurements (Detail) - KRW (₩) ₩ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018
Disclosure of detailed information about financial instruments [line items] |  |
Beginning balance | ₩ 10,844,722 |
Ending balance | 11,000,665 | ₩ 10,844,722
Beginning balance | 15,170,209 |
Ending balance | 16,128,644 | 15,170,209
Financial assets at fair value through profit or loss [member] |  |
Disclosure of detailed information about financial instruments [line items] |  |
Beginning balance | 777,685 |
Ending balance | 632,324 | 777,685
Recurring fair value measurement [Member] | Level 3 [Member] | Financial assets at fair value through profit or loss [member] |  |
Disclosure of detailed information about financial instruments [line items] |  |
Beginning balance | 163,600 |
Purchases | 584,671 |
Reclassification | 225,873 |
Disposal | (485,419) |
Amount recognized in profit or loss | 6,416 |
Amount recognized in other comprehensive income | 0 |
Ending balance | 495,141 | 163,600
Recurring fair value measurement [Member] | Level 3 [Member] | Derivative financial liabilities [member] |  |
Disclosure of detailed information about financial instruments [line items] |  |
Beginning balance | 10,183 | 17,725
Changes in accounting policy |  | 0
Purchases |  | 0
Reclassification |  | 0
Changes in scope of consolidation |  | 0
Disposal |  | 0
Amount recognized in profit or loss | 14,462 | (17,255)
Amount recognized in other comprehensive income | 13,509 | 9,713
Ending balance | 17,788 | 10,183
Recurring fair value measurement [Member] | Level 3 [Member] | Financial liabilities designated as at fair value through profit or loss [member] |  |
Disclosure of detailed information about financial instruments [line items] |  |
Beginning balance | 7,758 | 5,051
Changes in accounting policy |  | 0
Purchases |  | 0
Reclassification |  | 0
Changes in scope of consolidation |  | 0
Disposal | (9,734) | 0
Amount recognized in profit or loss | 1,976 | 2,707
Ending balance |  | 7,758
Recurring fair value measurement [Member] | Level 3 [Member] | Financial assets at fair value through profit or loss [member] |  |
Disclosure of detailed information about financial instruments [line items] |  |
Beginning balance | 163,600 | 97,547
Changes in accounting policy |  | 32,745
Purchases |  | 21,365
Reclassification |  | 1,581
Disposal |  | (1,852)
Amount recognized in profit or loss |  | 12,214
Ending balance |  | 163,600
Recurring fair value measurement [Member] | Level 3 [Member] | Financial assets at fair value through other comprehensive income [member] |  |
Disclosure of detailed information about financial instruments [line items] |  |
Beginning balance | 311,536 | 238,517
Changes in accounting policy |  | 2,085
Purchases | 6,081 | 8,802
Reclassification | (444,782) | (296)
Changes in scope of consolidation |  | 364
Disposal | (941) | (1,099)
Amount recognized in profit or loss | 0 | 89
Amount recognized in other comprehensive income | 170,160 | 63,074
Ending balance | ₩ 42,054 | ₩ 311,536

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