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Intangible Assets - Additional Information (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure of detailed information about intangible assets [line items]
Acquisition cost	₩ 201,461
Remaining useful life of Frequency usage rights	3 years
Carrying amount of the 28 gegahertz frequency usage [member]
Disclosure of detailed information about intangible assets [line items]
Impairment loss	₩ 190,929
KT Skylife Co Ltd [member] | Intangible assets with indefinite useful life [member]
Disclosure of detailed information about intangible assets [line items]
Impairment loss	₩ 0
Individual assets or cash-generating units [member]
Disclosure of detailed information about intangible assets [line items]
Impairment loss		₩ 38,519
Discount rate		7.30%

X

- Definition

The amount of acquisition-related costs recognised as an expense for transactions that are recognised separately from the acquisition of assets and the assumption of liabilities in business combinations. [Refer: Business combinations [member]]

+ References

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The discount rate used in the current measurement of fair value less costs of disposal.

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The amount recognised as a reduction of the carrying amount of an asset or cash-generating unit to its recoverable amount. [Refer: Carrying amount [member]]

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- Definition

The useful life, measured as period of time, used for intangible assets other than goodwill. [Refer: Intangible assets other than goodwill]

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