Financial Instruments by Category - Summary of Gains or Losses Arising From Financial Instruments by Category (Parenthetical) (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of detailed information about financial instruments [line items]
Interest income recognized as operating revenue	₩ 244,796	₩ 93,078	₩ 115,686
Profit and loss from foreign currency transaction	17,175	79,653	24,915
BC Card Co., Ltd. [member]
Disclosure of detailed information about financial instruments [line items]
Interest income recognized as operating revenue	21,021	15,561	14,380
Profit and loss from foreign currency transaction	₩ 20,422	₩ 11,049	₩ (1,987)

The amount of income arising from interest.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 8
-IssueDate 2018-01-01
-Paragraph 23
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=8&date=2018-03-01&anchor=para_23_c&doctype=Standard
-URIDate 2018-03-16

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
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-Subparagraph e
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=8&date=2018-03-01&anchor=para_28_e&doctype=Standard
-URIDate 2018-03-16

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2018-01-01
-Paragraph B13
-Subparagraph e
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=12&date=2018-03-01&anchor=para_B13_e&doctype=Appendix&seq=2
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Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
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-IssueDate 2018-01-01
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-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_112_c&doctype=Standard
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