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Information About Non-controlling Interests - Summary of consolidated statements of cash flows (Detail) - KRW (₩) ₩ in Millions | 12 Months Ended
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Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
Disclosure of Summarized Consolidated Statements of Cash Flows of Subsidiaries [Line Items] |  |  |
Cash flows from operating activities | ₩ 5,065,796 | ₩ 5,503,289 | ₩ 3,597,065
Cash flows from investing activities | (2,845,437) | (4,620,508) | (4,838,643)
Cash flows from financing activities | (1,390,053) | (452,792) | 669,331
Net increase (decrease) in cash and cash equivalents | 837,126 | 430,492 | (570,530)
Cash and cash equivalents at beginning of year | 2,879,554 | 2,449,062 | 3,019,592
Exchange differences | 6,820 | 503 | 1,717
Cash and cash equivalents at end of year | 3,716,680 | 2,879,554 | 2,449,062
KT Skylife Co., Ltd. [member] |  |  |
Disclosure of Summarized Consolidated Statements of Cash Flows of Subsidiaries [Line Items] |  |  |
Cash flows from operating activities | 162,281 | 207,207 | 176,407
Cash flows from investing activities | (160,757) | (125,343) | (78,928)
Cash flows from financing activities | 9,510 | (50,811) | (79,455)
Net increase (decrease) in cash and cash equivalents | 11,034 | 31,053 | 18,024
Cash and cash equivalents at beginning of year | 129,748 | 98,695 | 80,672
Exchange differences |  |  | (1)
Cash and cash equivalents at end of year | 140,782 | 129,748 | 98,695
BC Card Co., Ltd. [member] |  |  |
Disclosure of Summarized Consolidated Statements of Cash Flows of Subsidiaries [Line Items] |  |  |
Cash flows from operating activities | (97,232) | 82,883 | (798,043)
Cash flows from investing activities | (30,579) | (74,430) | (7,733)
Cash flows from financing activities | 121,800 | (67,609) | 914,441
Net increase (decrease) in cash and cash equivalents | (6,011) | (59,156) | 108,665
Cash and cash equivalents at beginning of year | 375,796 | 435,047 | 326,482
Exchange differences | 358 | (95) | (100)
Cash and cash equivalents at end of year | 370,143 | 375,796 | 435,047
KTIS Corporation [Member] |  |  |
Disclosure of Summarized Consolidated Statements of Cash Flows of Subsidiaries [Line Items] |  |  |
Cash flows from operating activities | 61,770 | 50,892 | 13,809
Cash flows from investing activities | (9,923) | (17,636) | 9,813
Cash flows from financing activities | (32,762) | (32,872) | (29,199)
Net increase (decrease) in cash and cash equivalents | 19,085 | 384 | (5,577)
Cash and cash equivalents at beginning of year | 25,328 | 24,944 | 30,521
Cash and cash equivalents at end of year | 44,413 | 25,328 | 24,944
KTCS Corporation [Member] |  |  |
Disclosure of Summarized Consolidated Statements of Cash Flows of Subsidiaries [Line Items] |  |  |
Cash flows from operating activities | 44,551 | 55,146 | 19,423
Cash flows from investing activities | 1,661 | (5,901) | 13,245
Cash flows from financing activities | (25,211) | (26,948) | (35,578)
Net increase (decrease) in cash and cash equivalents | 21,001 | 22,297 | (2,910)
Cash and cash equivalents at beginning of year | 84,111 | 61,814 | 63,884
Exchange differences |  |  | 840
Cash and cash equivalents at end of year | 105,112 | 84,111 | 61,814
Nasmedia Co Ltd [Member] |  |  |
Disclosure of Summarized Consolidated Statements of Cash Flows of Subsidiaries [Line Items] |  |  |
Cash flows from operating activities | 35,867 | 8,116 | 22,015
Cash flows from investing activities | (22,210) | (30,910) | 3,845
Cash flows from financing activities | (11,803) | (11,077) | (11,136)
Net increase (decrease) in cash and cash equivalents | 1,854 | (33,871) | 14,724
Cash and cash equivalents at beginning of year | 52,277 | 86,133 | 71,396
Exchange differences | 45 | 15 | 13
Cash and cash equivalents at end of year | ₩ 54,176 | ₩ 52,277 | ₩ 86,133

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