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Investments in Associates and Joint Ventures - Summary of Reconciliation of Carrying Amount of Interests in the Associates and Joint Ventures (Detail) - KRW (₩) ₩ in Millions | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019
Disclosure Of Associates And Joint Ventures [Line Items] |  |
Book amount | ₩ 557,881 | ₩ 267,660
K Bank Inc. [member] |  |
Disclosure Of Associates And Joint Ventures [Line Items] |  |
Net assets | ₩ 488,819 | ₩ 204,472
Percentage of ownership | 34.00% | 10.00%
Share in net assets | ₩ 166,198 | ₩ 45,158
Intercompany transaction and others | 42,074 |
Book amount | 208,272 | 45,158
Korea Information & Technology Fund [member] |  |
Disclosure Of Associates And Joint Ventures [Line Items] |  |
Net assets | ₩ 510,464 | ₩ 491,924
Percentage of ownership | 33.30% | 33.30%
Share in net assets | ₩ 170,155 | ₩ 163,975
Book amount | 170,155 | 163,975
KT-IBKC future investment fund [member] |  |
Disclosure Of Associates And Joint Ventures [Line Items] |  |
Net assets | ₩ 32,379 | ₩ 28,200
Percentage of ownership | 50.00% | 50.00%
Share in net assets | ₩ 16,190 | ₩ 14,100
Book amount | 16,190 | 14,100
KT-CKP New Media Investment Fund [member] |  |
Disclosure Of Associates And Joint Ventures [Line Items] |  |
Net assets |  | ₩ 270
Percentage of ownership |  | 49.70%
Share in net assets |  | ₩ 134
Book amount |  | ₩ 134
Hyundai Robotics Co., Ltd. [member] |  |
Disclosure Of Associates And Joint Ventures [Line Items] |  |
Net assets | ₩ 301,566 |
Percentage of ownership | 10.00% |
Share in net assets | ₩ 30,157 |
Intercompany transaction and others | 20,779 |
Book amount | ₩ 50,936 |

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- Definition The amount of investments accounted for using the equity method. The equity method is a method of accounting whereby the investment is initially recognised at cost and adjusted thereafter for the post-acquisition change in the investor's share of net assets of the investee. The investor's profit or loss includes its share of the profit or loss of the investee. The investor's other comprehensive income includes its share of the other comprehensive income of the investee. [Refer: At cost [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 8 -IssueDate 2020-01-01 -Paragraph 24 -Subparagraph a -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=8&code=ifrs-tx-2020-en-r&anchor=para_24_a&doctype=Standard -URIDate 2020-01-01 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 12 -IssueDate 2020-01-01 -Paragraph B16 -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=12&code=ifrs-tx-2020-en-r&anchor=para_B16&doctype=Appendix&subtype=B -URIDate 2020-01-01 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2020-01-01 -Paragraph 54 -Subparagraph e -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2020-en-r&anchor=para_54_e&doctype=Standard -URIDate 2020-01-01 + Details
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- Definition The proportion of ownership interest in an associate attributable to the entity. [Refer: Associates [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 27 -IssueDate 2020-01-01 -Paragraph 17 -Subparagraph b -Clause iii -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=27&code=ifrs-tx-2020-en-r&anchor=para_17_b_iii&doctype=Standard -URIDate 2020-01-01 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 27 -IssueDate 2020-01-01 -Paragraph 16 -Subparagraph b -Clause iii -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=27&code=ifrs-tx-2020-en-r&anchor=para_16_b_iii&doctype=Standard -URIDate 2020-01-01 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 12 -IssueDate 2020-01-01 -Paragraph 21 -Subparagraph a -Clause iv -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=12&code=ifrs-tx-2020-en-r&anchor=para_21_a_iv&doctype=Standard -URIDate 2020-01-01 + Details
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