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Information About Non-controlling Interests - Summary of Financial Information on Subsidiaries (Detail) - KRW (₩) ₩ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
Disclosure of subsidiaries [Line Items] |  |  |  |
Current assets | ₩ 9,678,243 | ₩ 9,716,020 |  |
Non-current assets | 20,067,196 | 20,948,278 |  |
Current liabilities | 9,458,104 | 9,523,137 |  |
Non-current liabilities | 7,238,205 | 8,358,443 |  |
Equity | 13,049,130 | 12,782,718 | ₩ 12,156,131 | ₩ 11,787,557
Accumulated non-controlling interests | 1,391,764 | 1,352,844 |  |
Operating revenue | 23,546,929 | 23,120,878 | 22,699,856 |
Profit or loss for the year | 546,341 | 795,117 | 624,685 |
Total comprehensive income | 478,053 | 789,447 | 555,850 |
The profit or loss allocated to non-controlling interests | 84,782 | 86,755 | 78,324 |
Cash flows from operating activities | 3,877,749 | 4,770,750 | 4,229,965 |
Cash flows from investing activities | (3,483,245) | (3,484,958) | (2,401,868) |
Net (decrease)/increase in cash and cash equivalents | ₩ (972,129) | ₩ 340,847 | ₩ 670,801 |
KT Skylife Co., Ltd. [member] |  |  |  |
Disclosure of subsidiaries [Line Items] |  |  |  |
Non-controlling Interests rate(%) | 49.73% | 49.73% | 49.73% |
Current assets | ₩ 324,632 | ₩ 352,980 | ₩ 279,480 |
Non-current assets | 468,261 | 424,968 | 431,814 |
Current liabilities | 185,995 | 151,329 | 143,511 |
Non-current liabilities | 24,555 | 80,123 | 74,339 |
Equity | 582,343 | 546,496 | 493,444 |
Accumulated non-controlling interests | 328,302 | 329,676 | 316,880 | 297,300
Operating revenue | 687,752 | 668,945 | 668,521 |
Profit or loss for the year | 57,314 | 68,863 | 72,987 |
Total comprehensive income | 55,586 | 68,785 | 73,147 |
The profit or loss allocated to non-controlling interests | 9,395 | 22,445 | 27,032 |
Cash flows from operating activities | 99,269 | 155,399 | 157,762 |
Cash flows from investing activities | (81,758) | (210,480) | (92,350) |
Cash flows from financing activities before dividend paid to non-controlling interests | (19,739) | (16,647) | (35,984) |
Dividend paid to non-controlling interests | (9,817) | (8,279) | (8,325) |
Net (decrease)/increase in cash and cash equivalents | ₩ (2,228) | ₩ (71,728) | ₩ 29,428 |
BC Card Co., Ltd. [member] |  |  |  |
Disclosure of subsidiaries [Line Items] |  |  |  |
Non-controlling Interests rate(%) | 30.46% | 30.46% | 30.46% |
Current assets | ₩ 3,225,262 | ₩ 2,945,584 | ₩ 2,291,047 |
Non-current assets | 823,001 | 705,480 | 672,905 |
Current liabilities | 2,868,669 | 2,530,832 | 1,882,363 |
Non-current liabilities | 86,369 | 71,571 | 63,271 |
Equity | 1,093,225 | 1,048,661 | 1,018,318 |
Accumulated non-controlling interests | 339,067 | 329,338 | 322,921 | 292,931
Operating revenue | 3,628,995 | 3,567,512 | 3,504,946 |
Profit or loss for the year | 156,109 | 163,131 | 218,969 |
Total comprehensive income | 141,719 | 178,744 | 188,360 |
The profit or loss allocated to non-controlling interests | 43,961 | 47,068 | 62,943 |
Cash flows from operating activities | 108,203 | 92,818 | 128,927 |
Cash flows from investing activities | (568,518) | (37,313) | 73,118 |
Cash flows from financing activities before dividend paid to non-controlling interests | (97,221) | (147,306) | (75,121) |
Dividend paid to non-controlling interests | (29,490) | (44,637) | (22,650) |
Gain or loss foreign currency translation | (184) | (178) |  |
Net (decrease)/increase in cash and cash equivalents | ₩ (557,536) | ₩ (91,801) | ₩ 126,924 |
KT Powertel Co., Ltd. [member] |  |  |  |
Disclosure of subsidiaries [Line Items] |  |  |  |
Non-controlling Interests rate(%) | 55.15% | 55.15% | 55.15% |
Current assets | ₩ 73,527 | ₩ 69,046 | ₩ 65,739 |
Non-current assets | 41,598 | 44,679 | 47,776 |
Current liabilities | 18,450 | 17,910 | 16,016 |
Non-current liabilities | 487 | 1,989 | 5,166 |
Equity | 96,188 | 93,826 | 92,333 |
Accumulated non-controlling interests | 53,053 | 51,751 | 50,926 | 70,231
Operating revenue | 69,234 | 81,390 | 104,527 |
Profit or loss for the year | 2,112 | 202 | (32,417) |
Total comprehensive income | 2,362 | 202 | (32,417) |
The profit or loss allocated to non-controlling interests | 1,165 | 112 | (17,880) |
Cash flows from operating activities | 13,895 | 7,271 | (12,016) |
Cash flows from investing activities | (17,354) | (8,191) | 10,691 |
Cash flows from financing activities before dividend paid to non-controlling interests |  |  | (2,015) |
Dividend paid to non-controlling interests |  |  | (1,118) |
Net (decrease)/increase in cash and cash equivalents | ₩ (3,459) | ₩ (920) | ₩ (3,340) |
KT Hitel Co., Ltd. [member] |  |  |  |
Disclosure of subsidiaries [Line Items] |  |  |  |
Non-controlling Interests rate(%) | 32.87% | 35.27% | 36.30% |
Current assets | ₩ 150,368 | ₩ 158,210 | ₩ 157,355 |
Non-current assets | 107,872 | 90,992 | 78,402 |
Current liabilities | 49,922 | 45,277 | 33,656 |
Non-current liabilities | 3,021 | 1,664 | 282 |
Equity | 205,297 | 202,261 | 201,819 |
Accumulated non-controlling interests | 53,146 | 51,798 | 50,689 | 51,136
Operating revenue | 227,884 | 198,994 | 162,155 |
Profit or loss for the year | 3,225 | 4,298 | 7,258 |
Total comprehensive income | 3,036 | 1,399 | 6,769 |
The profit or loss allocated to non-controlling interests | 870 | 1,274 | (608) |
Cash flows from operating activities | 28,320 | 28,987 | 22,556 |
Cash flows from investing activities | (36,086) | (33,238) | (19,949) |
Gain or loss foreign currency translation | (47) | 3 |  |
Net (decrease)/increase in cash and cash equivalents | ₩ (7,766) | ₩ (4,251) | ₩ 2,607 |
KT Telecop Co., Ltd. [member] |  |  |  |
Disclosure of subsidiaries [Line Items] |  |  |  |
Non-controlling Interests rate(%) | 13.18% | 13.18% | 13.18% |
Current assets | ₩ 73,023 | ₩ 63,802 | ₩ 58,457 |
Non-current assets | 191,330 | 201,751 | 210,734 |
Current liabilities | 90,569 | 53,903 | 82,353 |
Non-current liabilities | 41,064 | 78,441 | 52,613 |
Equity | 132,720 | 133,209 | 134,225 |
Accumulated non-controlling interests | 103,468 | 103,532 | 103,428 | ₩ 104,821
Operating revenue | 317,591 | 315,948 | 302,844 |
Profit or loss for the year | 2,885 | 143 | (7,593) |
Total comprehensive income | (490) | 143 | (7,593) |
The profit or loss allocated to non-controlling interests | 381 | 19 | (1,000) |
Cash flows from operating activities | 57,262 | 60,461 | 36,216 |
Cash flows from investing activities | (43,483) | (45,243) | (91,846) |
Cash flows from financing activities before dividend paid to non-controlling interests |  |  | (32,491) |
Net (decrease)/increase in cash and cash equivalents | ₩ 13,779 | ₩ 15,218 | ₩ (88,121) |

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