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Cash Generated from Operations - Summary of Cash Flows from Operating Activities (Detail) - KRW (₩) ₩ in Millions | 12 Months Ended
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Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Cash flows from (used in) operating activities [abstract] |  |  |
Profit for the year | ₩ 719,412 | ₩ 546,341 | ₩ 831,845
Adjustments to reconcile net income |  |  |
Income tax expense | 314,565 | 270,656 | 334,910
Interest income | (265,817) | (108,639) | (130,066)
Interest expense | 296,894 | 302,464 | 337,219
Dividends income | (2,910) | (4,785) | (3,926)
Depreciation | 2,735,413 | 2,802,531 | 2,821,779
Amortization of intangible assets | 629,526 | 635,150 | 599,721
Provision for severance benefits | 245,926 | 218,966 | 217,255
Impairment losses on trade receivables | 113,064 | 45,704 | 92,711
Share of net profit or loss of associates and joint ventures | 5,912 | 15,480 | (2,547)
Loss (gain) on disposal of associates and joint ventures | (3,737) | 979 | (1,450)
Impairment loss of associates and joint ventures |  | 3,662 | 17,128
Loss on disposal of property and equipment and investment in properties | 68,688 | 150,293 | 74,913
Loss (gain) on disposal of intangible assets | (4,256) | 4,271 | 7,703
Loss on impairment of intangible assets | 12,997 | 116,095 | 135,264
Loss on foreign currency translation | 68,952 | (213,341) | 109,784
Loss(gain) on valuation and settlement of derivatives, net | (92,210) | 268,094 | (117,181)
Gain on disposal of financial assets at fair value through profit or loss | (1,712) |  |
Gain on valuation of financial assets at fair value through profit or loss | (10,768) |  |
Gain on disposal of financial assets at amortized cost | (44) |  |
Impairment losses on available-for-sale financial assets |  | 9 | 966
Gain on disposal of available-for-sale financial assets |  | (89,598) | (22,695)
Others | (55,969) | (251,193) | 64,863
Changes in operating assets and liabilities |  |  |
Decrease(increase) in trade receivables | (81,217) | (303,340) | 216,818
Decrease(increase) in other receivables | 356,643 | (346,013) | (779,803)
Decrease(increase) in other current assets | (123,258) | 11,792 | 48,549
Decrease(increase) in other non-current assets | 19,556 | (43,790) | (51,765)
Decrease(increase) in inventories | (480,543) | (205,403) | 167,873
Increase(decrease) in trade payables | (167,841) | 162,110 | (114,838)
Increase(decrease) in other payables | (448,301) | 214,689 | 706,771
Increase in other current liabilities | 291,548 | 288,553 | 37,798
Increase in other non-current liabilities | 144,072 | 174,618 | 30,762
Decrease(Increase) in provisions | 85,946 | (12,574) | (12,583)
Decrease(Increase) in deferred revenue | 48,201 | (13,086) | (69,179)
Increase in plan assets | (53,301) | (203,420) | (224,244)
Payment of severance benefits | (153,209) | (118,391) | (121,835)
Cash generated from operations (1+2+3) | ₩ 4,212,222 | ₩ 4,318,884 | ₩ 5,202,520

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