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Financial Income and Costs - Summary of Details of Financial Expense (Detail) - KRW (₩) ₩ in Millions | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Disclosure Of Finance Income [line items] |  |  |
Interest expenses | ₩ 302,464 | ₩ 337,219 | ₩ 385,925
Loss on foreign currency transactions | 40,303 | 37,936 | 42,831
Loss on foreign currency translation | 12,239 | 121,949 | 175,613
Loss on settlement of derivatives | 58,569 | 632 | 6,280
Loss on valuation of derivatives | 209,582 | 138 | 1,733
Impairment loss on available-for-sale financial assets | 6,137 | 966 |
Others | 1,010 | 409 | 28,605
Total | 644,531 | 515,087 | 645,331
Loans and receivables [member] |  |  |
Disclosure Of Finance Income [line items] |  |  |
Loss on disposal of trade receivables | 20,351 | 15,838 | 2,539
Available-for-sale [member] |  |  |
Disclosure Of Finance Income [line items] |  |  |
Loss on disposal of trade receivables | (89,598) | (22,695) | (131,045)
Impairment loss on available-for-sale financial assets | ₩ 9 | ₩ 966 | ₩ 1,805

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