Commitments and Contingencies - Summary of Guarantees Provided by the Group for Third Parties (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022
Disclosure of detailed information about borrowings [line items]
Used amount	₩ 10,218,165	₩ 10,006,685
KT Estate Inc. [member] \| Hana Bank [Member] \| Guarantees [member]
Disclosure of detailed information about borrowings [line items]
Subject to payment guarantees	Wonju Bando U-bora Mark Bridge Buyer
Limit	₩ 103,000
Used amount	₩ 55,314
KT Engineering Co Ltd [Member] \| Shinhan Bank [member] \| Guarantees [member]
Disclosure of detailed information about borrowings [line items]
Subject to payment guarantees	Gasan Solar Power Plant Inc.
Limit	₩ 4,700
Used amount	₩ 364
KT Engineering Co Ltd [Member] \| Suhyup Bank [Member] \| Guarantees [member]
Disclosure of detailed information about borrowings [line items]
Subject to payment guarantees	Korea Cell Inc.
Limit	₩ 3,250
Used amount	₩ 50
KT Engineering Co Ltd [Member] \| Suhyup Bank One [Member] \| Guarantees [member]
Disclosure of detailed information about borrowings [line items]
Subject to payment guarantees	San-Ya Agricultural Association Corporation
Limit	₩ 3,250
Used amount	₩ 51
KT Alpha Co Ltd [Member] \| T-commerce cash payers [Member] \| Guarantees [member]
Disclosure of detailed information about borrowings [line items]
Subject to payment guarantees	Cash payers
Limit	₩ 821
Used amount	₩ 0
Nasmedia, Co., Ltd. [Member] \| Korea Securities Finance Corp [Member] \| Guarantees [member]
Disclosure of detailed information about borrowings [line items]
Subject to payment guarantees	Stockholders Association Members
Limit	₩ 1,104
Used amount	₩ 610
Bottom of range [member] \| KT Estate Inc. [member] \| Hana Bank [Member] \| Guarantees [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Aug. 5, 2022
Bottom of range [member] \| KT Engineering Co Ltd [Member] \| Shinhan Bank [member] \| Guarantees [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Jan. 7, 2010
Bottom of range [member] \| KT Engineering Co Ltd [Member] \| Suhyup Bank [Member] \| Guarantees [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Feb. 17, 2014
Bottom of range [member] \| KT Engineering Co Ltd [Member] \| Suhyup Bank One [Member] \| Guarantees [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Feb. 17, 2014
Bottom of range [member] \| KT Alpha Co Ltd [Member] \| T-commerce cash payers [Member] \| Guarantees [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Apr. 14, 2023
Top of range [member] \| KT Estate Inc. [member] \| Hana Bank [Member] \| Guarantees [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Feb. 28, 2025
Top of range [member] \| KT Engineering Co Ltd [Member] \| Shinhan Bank [member] \| Guarantees [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Jan. 8, 2025
Top of range [member] \| KT Engineering Co Ltd [Member] \| Suhyup Bank [Member] \| Guarantees [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Feb. 16, 2024
Top of range [member] \| KT Engineering Co Ltd [Member] \| Suhyup Bank One [Member] \| Guarantees [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Feb. 16, 2024
Top of range [member] \| KT Alpha Co Ltd [Member] \| T-commerce cash payers [Member] \| Guarantees [member]
Disclosure of detailed information about borrowings [line items]
Maturity	Apr. 12, 2024

The amount of outstanding funds that the entity is obligated to repay.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2023-01-01
-Paragraph 55
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2023-en-r&anchor=para_55&doctype=Standard
-URIDate 2023-03-23

+ Details

Name:	ifrs-full_Borrowings
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The maturity of borrowings. [Refer: Borrowings]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IFRS
-Number 7
-IssueDate 2023-01-01
-Paragraph 7
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2023-en-r&anchor=para_7&doctype=Standard
-URIDate 2023-03-23

+ Details

Name:	ifrs-full_BorrowingsMaturity
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with members defined in one or many axes of the table.

+ References

No definition available.

+ Details

Name:	ifrs-full_DisclosureOfDetailedInformationAboutBorrowingsLineItems
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of contractual undiscounted cash flows for gross commitments to receive a loan.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Name IFRS
-Number 7
-IssueDate 2023-01-01
-Paragraph B11D
-Subparagraph e
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2023-en-r&anchor=para_B11D_e&doctype=Appendix&subtype=B
-URIDate 2023-03-23

+ Details

Name:	ifrs-full_GrossLoanCommitments
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Description of subject to payment guarantees.

+ References

No definition available.

+ Details

Name:	kt_DescriptionOfSubjectToPaymentGuarantees
Namespace Prefix:	kt_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	ifrs-full_SignificantInvestmentsInSubsidiariesAxis=kt_KtEstateIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_CounterpartiesAxis=kt_HanaBankMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	kt_ContingentLiabilitiesGuaranteeBeneficiaryAxis=ifrs-full_GuaranteesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_SignificantInvestmentsInSubsidiariesAxis=kt_KtEngineeringCoLtdMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_CounterpartiesAxis=kt_ShinhanBankMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_CounterpartiesAxis=kt_SuhyupBankMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_CounterpartiesAxis=kt_SuhyupBankOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_SignificantInvestmentsInSubsidiariesAxis=kt_KtAlphaCoLtdMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_CounterpartiesAxis=kt_TCommerceCashPayersMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_SignificantInvestmentsInSubsidiariesAxis=kt_NasmediaCoLtdMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_CounterpartiesAxis=kt_KoreaSecuritiesFinanceCorpMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_RangeAxis=ifrs-full_BottomOfRangeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_RangeAxis=ifrs-full_TopOfRangeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: