Investments in Associates and Joint Ventures - Summary of Changes in Investments in Associates and Joint Ventures (Parenthetical) (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Disclosure Of Associates And Joint Ventures [Line Items]
Share gain from associates and joint ventures	₩ (17,285)	₩ 116,061	₩ 18,041
KT Investment Co., Ltd. [member]
Disclosure Of Associates And Joint Ventures [Line Items]
Share gain from associates and joint ventures	₩ 464	₩ 113	₩ 279

The entity's share of the profit (loss) of associates and joint ventures accounted for using the equity method. [Refer: Associates [member]; Investments accounted for using equity method; Joint ventures [member]; Profit (loss)]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 8
-IssueDate 2022-03-24
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Note Effective on first application of IFRS 9
-Name IFRS
-Number 4
-IssueDate 2022-03-24
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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