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Other Financial Assets and Liabilities - Additional Information (Detail) - KRW (₩) ₩ in Millions | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Disclosure of detailed information about financial instruments [Line Items] |  |  |
Ineffective portion recognized in profit or loss cash flow hedge valuation gain | ₩ 1,961 | ₩ 1,637 | ₩ 2,663
Korea Software Financial Cooperative [Member] |  |  |
Disclosure of detailed information about financial instruments [Line Items] |  |  |
Available-for-sale financial assets investment amount | ₩ 1,000 |  |

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