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Related Party Transactions - Summary of Significant Transactions with Related Parties (Detail) - KRW (₩) ₩ in Millions | 12 Months Ended
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Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Disclosure of transactions between related parties [line items] |  |  |
Sales | ₩ 23,416 | ₩ 24,312 | ₩ 37,282
Purchases | 19,055 | 128,252 | 156,259
K-Realty CR-REITs No.1 [member] |  |  |
Disclosure of transactions between related parties [line items] |  |  |
Sales | 1,302 | 2,088 | 2,233
Purchases | 0 | 31,984 | 35,532
MOS GS Co., Ltd. [member] |  |  |
Disclosure of transactions between related parties [line items] |  |  |
Sales |  | 493 | 704
Purchases |  | 12,023 | 16,946
MOS Daegu Co., Ltd. [member] |  |  |
Disclosure of transactions between related parties [line items] |  |  |
Sales |  | 229 | 335
Purchases |  | 8,775 | 8,514
MOS Chungcheong Co., Ltd. [member] |  |  |
Disclosure of transactions between related parties [line items] |  |  |
Sales |  | 540 | 455
Purchases |  | 9,159 | 15,542
MOS Gangnam Co., Ltd. [member] |  |  |
Disclosure of transactions between related parties [line items] |  |  |
Sales |  | 333 | 484
Purchases |  | 11,549 | 16,380
MOS GB Co., Ltd. [member] |  |  |
Disclosure of transactions between related parties [line items] |  |  |
Sales |  | 1,378 | 987
Purchases |  | 16,519 | 21,651
MOS BS Co., Ltd. [member] |  |  |
Disclosure of transactions between related parties [line items] |  |  |
Sales |  | 324 | 460
Purchases |  | 11,193 | 15,957
MOS Honam Co., Ltd. [member] |  |  |
Disclosure of transactions between related parties [line items] |  |  |
Sales |  | 331 | 493
Purchases |  | 10,499 | 14,294
Others [member] |  |  |
Disclosure of transactions between related parties [line items] |  |  |
Sales |  | 2,888 | 1,149
Purchases |  | 9,547 | 11,384
K Bank Inc. [member] |  |  |
Disclosure of transactions between related parties [line items] |  |  |
Sales | 17,815 | 15,705 | 29,939
Purchases | 8,524 | 7,004 | 59
NgeneBio [member] |  |  |
Disclosure of transactions between related parties [line items] |  |  |
Sales | 1,498 | ₩ 3 | ₩ 43
Purchases | 10,531 |  |
K-Realty CR-REITs No.10 [member] |  |  |
Disclosure of transactions between related parties [line items] |  |  |
Sales | ₩ 2,801 |  |

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