Trade and Other Receivables - Summary of Other Receivables (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2017	Dec. 31, 2016
Disclosure of financial assets [line items]
Loans	₩ 9,653,443
Other receivables	3,450,577	₩ 3,100,811
Other assets [member]
Disclosure of financial assets [line items]
Less Allowance for doubtful accounts	(84,372)	(141,616)
Gross carrying amount [member]
Disclosure of financial assets [line items]
Loans	84,682	80,308
Receivables	2,970,346	2,709,177
Accrued income	12,186	9,903
Refundable deposits	391,458	390,035
Loans receivable	34,273	10,355
Finance lease receivables	20,526	16,280
Others	₩ 21,478	₩ 26,369

The amount of asset representing income that has been earned but is not yet received.

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

Name:	ifrs-full_AccruedIncome
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of an allowance account used to record impairments to financial assets due to credit losses. [Refer: Financial assets]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Note Expiry date 2018-01-01
-Name IFRS
-Number 7
-IssueDate 2017-01-01
-Paragraph 16
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=7&date=2017-03-02&anchor=para_16&doctype=Standard&book=B
-URIDate 2017-03-09

+ Details

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

- Definition

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

+ References

No definition available.

+ Details

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

- Definition

The amount of receivables related to finance leases.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2017-01-01
-Paragraph 55
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_55&doctype=Standard
-URIDate 2017-03-09

+ Details

Name:	ifrs-full_FinanceLeaseReceivables
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of loans and advances the entity has made to customers.

+ References

+ Details

Name:	ifrs-full_LoansAndAdvancesToCustomers
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of non-derivative financial assets with fixed or determinable payments that are not quoted in an active market, other than: (a) those that the entity intends to sell immediately or in the near term, which shall be classified as held for trading, and those that the entity, upon initial recognition, designates as at fair value through profit or loss; (b) those that the entity, upon initial recognition, designates as available for sale; or (c) those for which the holder may not recover substantially all of its initial investment, other than because of credit deterioration, which shall be classified as available for sale. An interest acquired in a pool of assets that are not loans or receivables (for example, an interest in a mutual fund or a similar fund) is not a loan or receivable. [Refer: Derivative financial assets]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Note Expiry date 2018-01-01
-Name IFRS
-Number 7
-IssueDate 2017-01-01
-Paragraph 8
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=7&date=2017-03-02&anchor=para_8_c&doctype=Standard&book=B
-URIDate 2017-03-09

+ Details

Name:	ifrs-full_LoansAndReceivables
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount receivable by the entity that it does not separately disclose in the same statement or note.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Name IAS
-Number 1
-IssueDate 2017-01-01
-Paragraph 78
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_78_b&doctype=Standard
-URIDate 2017-03-09

+ Details

Name:	ifrs-full_OtherReceivables
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of receivables due from related parties. [Refer: Related parties [member]]

+ References

+ Details

Name:	ifrs-full_TradeAndOtherReceivablesDueFromRelatedParties
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Miscellaneous In Other Receivables

+ References

No definition available.

+ Details

Name:	kt_MiscellaneousInOtherReceivables
Namespace Prefix:	kt_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Refundable deposits.

+ References

No definition available.

+ Details

Name:	kt_RefundableDeposits
Namespace Prefix:	kt_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	ifrs-full_ClassesOfAssetsAxis=ifrs-full_OtherAssetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_CarryingAmountAccumulatedDepreciationAmortisationAndImpairmentAndGrossCarryingAmountAxis=ifrs-full_GrossCarryingAmountMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: