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Operating Expenses - Summary of Operating Expenses (Detail) - KRW (₩) ₩ in Millions | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Profit or loss [abstract] |  |  |
Salaries and wages | ₩ 3,568,456 | ₩ 3,477,596 | ₩ 3,303,484
Depreciation | 2,745,969 | 2,762,773 | 2,756,131
Amortization of intangible assets | 618,533 | 582,493 | 582,467
Commissions | 1,085,865 | 1,099,429 | 1,036,852
Interconnection charges | 640,612 | 690,285 | 689,293
International interconnection fee | 214,058 | 216,633 | 231,060
Purchase of inventories | 4,053,693 | 3,407,263 | 3,963,036
Changes of inventories | (187,439) | 162,323 | (198,028)
Sales commission | 2,201,778 | 1,968,035 | 1,856,595
Service cost | 1,428,405 | 1,322,337 | 1,163,887
Utilities | 323,313 | 323,406 | 319,303
Taxes and dues | 279,574 | 255,480 | 256,958
Rent | 448,772 | 455,457 | 469,950
Insurance premium | 69,384 | 178,231 | 211,104
Installation fee | 146,783 | 156,669 | 249,413
Advertising expenses | 197,114 | 185,560 | 177,348
Research and development expenses | 168,635 | 167,881 | 183,821
Card service cost | 3,094,894 | 3,049,559 | 2,959,765
Others | 1,379,438 | 1,319,688 | 1,410,349
Total | ₩ 22,477,837 | ₩ 21,781,098 | ₩ 21,622,788

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- Definition The amount of amortisation expense. Amortisation is the systematic allocation of depreciable amounts of intangible assets over their useful lives. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 1 -IssueDate 2017-01-01 -Paragraph 112 -Subparagraph c -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_112_c&doctype=Standard -URIDate 2017-03-09 + Details
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- Definition The amount of depreciation expense. Depreciation is the systematic allocation of depreciable amounts of tangible assets over their useful lives. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 1 -IssueDate 2017-01-01 -Paragraph 112 -Subparagraph c -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_112_c&doctype=Standard -URIDate 2017-03-09 + Details
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- Definition The amount of expense arising from purchased insurance. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 1 -IssueDate 2017-01-01 -Paragraph 112 -Subparagraph c -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_112_c&doctype=Standard -URIDate 2017-03-09 + Details
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- Definition The amount of miscellaneous other operating expenses. [Refer: Other operating income (expense)] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 1 -IssueDate 2017-01-01 -Paragraph 112 -Subparagraph c -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_112_c&doctype=Standard -URIDate 2017-03-09 + Details
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- Definition The amount of all operating expenses. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 1 -IssueDate 2017-01-01 -Paragraph 85 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_85&doctype=Standard -URIDate 2017-03-09 + Details
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- Definition The amount of expense recognised on rental activities. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 1 -IssueDate 2017-01-01 -Paragraph 85 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_85&doctype=Standard -URIDate 2017-03-09 + Details
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- Definition The amount of expenditure directly attributable to research or development activities, recognised in profit or loss. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 38 -IssueDate 2017-01-01 -Paragraph 126 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=38&date=2017-03-01&anchor=para_126&doctype=Standard -URIDate 2017-03-09 + Details
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- Definition The amount of expense arising from services. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 1 -IssueDate 2017-01-01 -Paragraph 85 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_85&doctype=Standard -URIDate 2017-03-09 + Details
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- Definition A class of employee benefits expense that represents wages and salaries. [Refer: Employee benefits expense] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 19 -IssueDate 2017-01-01 -Paragraph 9 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_9&doctype=Standard -URIDate 2017-03-09 + Details
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