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Related Parties - Summary of Transactions Between Related Parties (Details) - KRW (₩)
₩ in Millions
 12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Dec. 31, 2019
Dongducheon Dream Power Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales ₩ 19,923 ₩ 7,757 ₩ 7,071
Electricity purchase 750,148 552,692 689,510
Outstanding balances for related party transactions [abstract]      
Trade receivables 6,282 388  
Trade payables 114,613 65,794  
Non-trade receivables and others 493 213  
Korea Gas Corporation      
Disclosure of transactions between related parties [line items]      
Electricity sales 96,362 97,685 116,484
Purchase of power generation fuel 5,646,713 3,270,972 4,049,486
Outstanding balances for related party transactions [abstract]      
Trade receivables 10,015 9,969  
Trade payables 800,509 428,763  
Non-trade receivables and others 187 95  
Non-trade payables and others 759 617  
Daejung Offshore Wind Power Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 46 32 1
Outstanding balances for related party transactions [abstract]      
Non-trade receivables and others 77 31  
Daegu Photovoltaic Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 207 325 327
REC purchase 3,532 3,313 3,626
Outstanding balances for related party transactions [abstract]      
Trade payables 115 57  
Haeng Bok Do Si Photovoltaic Power Co Ltd      
Disclosure of transactions between related parties [line items]      
REC purchase 393 370 450
Korea Electric Power Industrial Development Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Service sales 11,208 10,833 11,085
Electricity metering service fee 241,925 212,366 245,057
Outstanding balances for related party transactions [abstract]      
Trade receivables 269 508  
Trade payables 873 133  
Non-trade receivables and others 15 16  
Non-trade payables and others 5,880 3,779  
Goseong Green Power Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 514,470 47,701 19,245
Electricity purchase 987,540 0 32
Outstanding balances for related party transactions [abstract]      
Trade receivables 495 2,181  
Trade payables 218,627    
Non-trade receivables and others 76,855 9,214  
Non-trade payables and others 59,987 64,986  
Gangneung Eco Power Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Service sales 14,200 10,178 7,446
Outstanding balances for related party transactions [abstract]      
Trade receivables 826 661  
Non-trade receivables and others 465 146  
Non-trade payables and others 97    
Shin Pyeongtaek Power Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 23,501 20,791 21,218
Electricity purchase 653,306 520,737 119,162
Outstanding balances for related party transactions [abstract]      
Trade receivables 1,788 1,348  
Trade payables 79,828 47,948  
Non-trade receivables and others 3,116 2,823  
Non-trade payables and others 99 85  
Noeul Green Energy Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 30 30 30
REC purchase 10,014 10,634 22,767
Outstanding balances for related party transactions [abstract]      
Trade receivables 3 3  
Non-trade receivables and others 1,169 969  
Samcheok Eco Materials Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 620 700 627
Electricity purchase 13,612 10,713 9,425
Outstanding balances for related party transactions [abstract]      
Trade receivables 52 47  
YTN Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 1,922 1,805 2,257
Service purchase 388 353 333
Outstanding balances for related party transactions [abstract]      
Trade receivables 99 97  
Busan Green Energy Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 49 34 18
Electricity purchase 18,996 18,678 13,811
Outstanding balances for related party transactions [abstract]      
Trade receivables 1 5  
Non-trade receivables and others 20,658 13,946  
Gunsan Bio Energy Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 20 102 4,755
Electricity purchase 0 24 3,022
Outstanding balances for related party transactions [abstract]      
Non-trade receivables and others 11,728    
Korea Electric Vehicle Charging Service      
Disclosure of transactions between related parties [line items]      
Electricity sales 3,059 1,956 1,029
Service purchase 393 581 536
Outstanding balances for related party transactions [abstract]      
Trade receivables 193 141  
Non-trade receivables and others 120 281  
Yaksu ESS Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Service purchase 1,715 217 1,191
Outstanding balances for related party transactions [abstract]      
Trade payables 1,374 739  
Gangwon Wind Power Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 1,865 2,109 2,433
Electricity purchase 19,623 23,350 24,116
Outstanding balances for related party transactions [abstract]      
Trade receivables 8 6  
Trade payables 4,293 2,678  
Gwangyang Green Energy Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 486 23 122
Outstanding balances for related party transactions [abstract]      
Non-trade receivables and others 532 1,356  
Bigeum Resident Photovoltaic Power Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 755 85 0
Outstanding balances for related party transactions [abstract]      
Trade receivables 922    
Hyundai Green Power Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Design service 11,934 17,257 13,106
Electricity purchase 0 349,778 507,662
Outstanding balances for related party transactions [abstract]      
Trade receivables 229 554  
Trade payables   9,825  
Korea Power Exchange      
Disclosure of transactions between related parties [line items]      
Service sales 39,796 25,919 7,670
Trading fees 86,716 87,361 120,509
Outstanding balances for related party transactions [abstract]      
Trade receivables 627 1,608  
Trade payables   1,362  
Non-trade receivables and others 1,300 24  
Non-trade payables and others 2,189 70,456  
Taebaek Wind Power Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Service sales 44 226 991
Electricity purchase 5,930 4,003 7,070
Outstanding balances for related party transactions [abstract]      
Trade payables 560 443  
Non-trade receivables and others   1,405  
Non-trade payables and others 262    
Taeback Guinemi Wind Power Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 26 37 77
Electricity purchase 5,910 5,023 349
Taebaek Guinemi Wind Power Co., Ltd      
Outstanding balances for related party transactions [abstract]      
Trade payables 670 413  
Non-trade payables and others   509  
Pyeongchang Wind Power Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 1,180 2,064 1,189
Electricity purchase 4,099 3,969 5,188
Outstanding balances for related party transactions [abstract]      
Trade receivables 4 3  
Daeryun Power Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 1,944 1,947 1,879
Electricity purchase 157,234 99,523 144,862
Outstanding balances for related party transactions [abstract]      
Trade receivables 213 189  
Trade payables 21,362 16,079  
Changjuk Wind Power Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 463 2,067 927
Electricity purchase 6,213 6,084 6,994
Outstanding balances for related party transactions [abstract]      
Trade payables 724 461  
Non-trade payables and others 295 309  
GS Donghae Electric Power Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 21,127 31,557 15,792
Electricity purchase 760,377 660,351 681,379
Outstanding balances for related party transactions [abstract]      
Trade receivables 383 386  
Trade payables 113,529 91,213  
Non-trade receivables and others 272 321  
Non-trade payables and others 17 36  
KNH Solar Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 14 16 17
Electricity purchase 3,222 3,564 3,377
Outstanding balances for related party transactions [abstract]      
Trade receivables 1 1  
Trade receivables 82 137  
Trade payables   14  
Non-trade payables and others   187  
S-Power Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Service sales 5,229 6,682 6,535
Electricity purchase 608,530 293,515 522,469
Outstanding balances for related party transactions [abstract]      
Trade payables 91,277 23,415  
Non-trade receivables and others 48 46  
PND Solar Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 416 409 407
Electricity purchase 5,502 5,234 557
Outstanding balances for related party transactions [abstract]      
Trade payables   58  
Hyundai Ecoenergy Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 187 167 117
Electricity purchase 25,762 17,777 6,810
Outstanding balances for related party transactions [abstract]      
Trade receivables 19 16  
Trade payables 732    
YeongGwang Yaksu Wind Electric Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 78 77 81
Electricity purchase 11,729 9,151 6,511
Outstanding balances for related party transactions [abstract]      
Trade receivables 6 8  
Korea Energy Solution Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 2 7 52
Electricity purchase 0 0 15
Gwangbaek Solar Power Investment Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity purchase 742 373 0
Green Energy Electricity Generation Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 0 14 0
Electricity purchase 1,238 0 0
Namjeongsusang Solar Power Operation Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 22 14 0
Electricity purchase 14,286 0 0
Hanwha Corporation-linked Sunlight Power Special Private Equity Investment Trust No. 1      
Disclosure of transactions between related parties [line items]      
Service sales 399 291 0
Muan Solar Park Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 232 57 0
Electricity purchase 31,017 0 0
Outstanding balances for related party transactions [abstract]      
Trade receivables   24  
Non-trade receivables and others 23    
Go deok Clean Energy Co., Ltd      
Outstanding balances for related party transactions [abstract]      
Non-trade receivables and others   1  
Suwon New Power Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 1,820 2,974 5,606
Outstanding balances for related party transactions [abstract]      
Trade receivables   2  
Non-trade receivables and others 1,198 712  
Muan Sunshine Solar Power Plant Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 52 30 0
Electricity purchase 15,900 0 0
Outstanding balances for related party transactions [abstract]      
Trade payables 1,748    
Nine Associates (Overseas)      
Disclosure of transactions between related parties [line items]      
Electricity sales and others 125,723 66,755 98,450
Haeng Bok Do Si Photovoltaic Power      
Disclosure of transactions between related parties [line items]      
Electricity sales 2 2 2
Energy Infra Asset Management Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 4,629 0 0
Service sales 2,657 0 0
Taebaek Gadeoksan Wind Power Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 295 0 0
Electricity purchase 16,360 0 0
Outstanding balances for related party transactions [abstract]      
Trade payables 8,397    
Non-trade receivables and others 119    
Non-trade payables and others 1,571    
ITR Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Service sales 3 0 0
Structure test network Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Service sales 5 0 0
Bitgoel Eco Energy Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 282 0 0
Outstanding balances for related party transactions [abstract]      
Non-trade receivables and others 27    
Anjwa Smart Farm & Solar City Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 624 0 0
Electricity purchase 24,601 0 0
Daewon Green Energy Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 155 0 0
Outstanding balances for related party transactions [abstract]      
Non-trade receivables and others 94    
Saemangeum Heemang Photovoltaic Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 13 0 0
UD four M Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 4 0 0
Dongbu Highway Solar Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 5 0 0
Electricity purchase 2,605 0 0
Outstanding balances for related party transactions [abstract]      
Trade receivables 1    
Trade payables 98    
Non-trade payables and others 90    
Seobu Highway Solar Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 8 0 0
Electricity purchase 2,936 0 0
Outstanding balances for related party transactions [abstract]      
Trade payables 177    
Non-trade payables and others 105    
SureDataLab Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 1 0 0
Hankook Electric Power Information Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 1 0 0
KOSTURE Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 1 0 0
Outstanding balances for related party transactions [abstract]      
Trade receivables 1    
Goesan Solar park Co., Ltd      
Disclosure of transactions between related parties [line items]      
Electricity purchase 6,209 0 0
Outstanding balances for related party transactions [abstract]      
Trade payables 73    
Jeju Gimnyeong Wind Power Co., Ltd      
Disclosure of transactions between related parties [line items]      
Electricity purchase 12,833 0 0
Outstanding balances for related party transactions [abstract]      
Trade payables 885    
Seoroseoro Sunny Power Plant Co Ltd      
Disclosure of transactions between related parties [line items]      
Electricity purchase 217 0 0
YuDang Solar Co., Ltd      
Disclosure of transactions between related parties [line items]      
Electricity purchase 3,495 0 0
One Associates (Overseas)      
Disclosure of transactions between related parties [line items]      
Electricity purchase 502 0 0
Four Associates (Overseas)      
Outstanding balances for related party transactions [abstract]      
Non-trade receivables and others 3,196 3,248  
Non-trade payables and others 502    
Naepo Green Energy Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 467 217 154
Outstanding balances for related party transactions [abstract]      
Trade receivables 42 56  
Cheongna Energy Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Service sales 16,469 13,791 9,922
Electricity purchase 57 66 58,747
Outstanding balances for related party transactions [abstract]      
Trade receivables 4,164 1,592  
Non-trade receivables and others 1,350 1,186  
Non-trade payables and others 1    
Dayone Energy Co., Ltd. (formerly, Hyundai Energy Co., Ltd.)      
Disclosure of transactions between related parties [line items]      
Service sales 8,159 4,816 3,437
Electricity purchase 5,409 1,120 2,847
Outstanding balances for related party transactions [abstract]      
Trade receivables 52 57  
Trade payables 1,009 10  
Non-trade receivables and others 13,297 11,749  
Non-trade payables and others 11,306 9,119  
Daegu Green Power Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 1,053 1,285 1,151
Electricity purchase 289,052 215,224 296,464
Outstanding balances for related party transactions [abstract]      
Trade receivables 71 44  
Trade payables 35,766 26,213  
Non-trade receivables and others 55 55  
KAPES, Inc.      
Disclosure of transactions between related parties [line items]      
Commission 413 476 504
Service purchase 64,140 219,673 142,511
Outstanding balances for related party transactions [abstract]      
Trade receivables 2 2  
Non-trade receivables and others   5,172  
Non-trade payables and others 2,121 20,577  
Honam Wind Power Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 71 502 657
Electricity purchase 4,807 4,382 5,306
Outstanding balances for related party transactions [abstract]      
Trade payables 575 216  
Non-trade payables and others   345  
Jeongam Wind Power Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 588 1,213 1,198
Electricity purchase 3,145 5,982 0
Outstanding balances for related party transactions [abstract]      
Non-trade receivables and others   162  
Non-trade payables and others   692  
Korea Power Engineering Service Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Service sales 339 203 348
Service purchase 1,315 1,594 1,774
Outstanding balances for related party transactions [abstract]      
Non-trade receivables and others 48 43  
Seokmun Energy Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Service sales 1,701 1,932 1,495
Electricity purchase 44,315 33,164 26,370
Outstanding balances for related party transactions [abstract]      
Trade receivables 34 62  
Trade payables 7,941 4,898  
Non-trade receivables and others 149 9,460  
Non-trade payables and others   9,559  
Incheon New Power Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Construction revenue 14 14 354
Chun-cheon Energy Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 2,329 2,657 2,397
Electricity purchase 327,536 222,069 313,471
Outstanding balances for related party transactions [abstract]      
Trade receivables 126 98  
Trade payables 41,410 27,428  
Non-trade receivables and others 167 165  
Yeonggwangbaeksu Wind Power Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 1,836 1,788 1,744
Electricity purchase 9,471 11,232 11,739
Outstanding balances for related party transactions [abstract]      
Trade receivables 6 8  
Trade payables 1,099 405  
Non-trade receivables and others 53 159  
Non-trade payables and others   1,747  
Yeonggwang Wind Power Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 818 793 705
Electricity purchase 21,004 24,103 11,940
Outstanding balances for related party transactions [abstract]      
Trade receivables 10 12  
Trade payables 730 886  
Non-trade receivables and others 59 54  
Non-trade payables and others   3,038  
Sam-Yang Photovoltaic Power Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 1,920 33 0
Electricity purchase 5,852 3,848 0
Outstanding balances for related party transactions [abstract]      
Trade receivables 5 5  
Non-trade payables and others   625  
NH-Amundi Global Infrastructure Investment Private Investment Trust 21      
Disclosure of transactions between related parties [line items]      
Service sales 1,727 1,388 0
KW Nuclear Components Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Service sales 2,598 1,639 721
Outstanding balances for related party transactions [abstract]      
Trade receivables   4  
KEPCO-Uhde Inc.      
Disclosure of transactions between related parties [line items]      
Electricity sales 10 8 15
Outstanding balances for related party transactions [abstract]      
Non-trade payables and others 10    
Busan Shinho Solar Power Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 376 353 452
REC purchase 7,895 7,296 7,843
Outstanding balances for related party transactions [abstract]      
Trade receivables 2 2  
Trade payables 281 135  
Non-trade payables and others   780  
Global Trade Of Power System Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Service purchase 323 337 502
Outstanding balances for related party transactions [abstract]      
Non-trade payables and others 7    
Expressway Solar-light Power Generation Co., Ltd.      
Disclosure of transactions between related parties [line items]      
REC purchase 3,146 2,472 3,067
Outstanding balances for related party transactions [abstract]      
Trade payables 102    
Daesan Green Energy Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 523 703 39
Electricity purchase 146,776 104,854 0
Outstanding balances for related party transactions [abstract]      
Trade receivables 11 11  
Trade payables 5,120 7,694  
Non-trade receivables and others 120 216  
Taebaek Gadeoksan Wind Power Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 2 3 0
Electricity purchase 5,080 0 0
Outstanding balances for related party transactions [abstract]      
Trade payables   2,473  
Non-trade receivables and others   5  
Non-trade payables and others   5  
Cheong-Song Noraesan Wind Power Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 30 29 6
Outstanding balances for related party transactions [abstract]      
Trade receivables 2 2  
Saemangeum Solar Power Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Service sales 1,141 2,846 2,230
Electricity purchase 5 0 0
Outstanding balances for related party transactions [abstract]      
Non-trade receivables and others 4,268 3,141  
Jaeun Resident Wind Power Plant Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 0 0 105
Dangjin Eco Power Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 32 33 4
Electricity purchase 4,139 3,953 0
Outstanding balances for related party transactions [abstract]      
Trade receivables 3 3  
Trade payables 276 326  
Bitsolar Energy Co., Ltd.,      
Disclosure of transactions between related parties [line items]      
Electricity sales 296 42 0
Electricity purchase 5,703 0 0
Outstanding balances for related party transactions [abstract]      
Non-trade receivables and others 7    
Non-trade payables and others 54    
Busan Industrial Solar Power Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity purchase 2,815 19 0
Outstanding balances for related party transactions [abstract]      
Trade receivables 1    
Trade payables 54 1  
Non-trade payables and others 24    
Haemodum Solar Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 6 4 0
Electricity purchase 1,625 967 0
Outstanding balances for related party transactions [abstract]      
Trade receivables 1    
Yeongam Solar Power Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 339 165 0
Electricity purchase 47,805 32,208 0
Outstanding balances for related party transactions [abstract]      
Trade receivables 29 26  
Trade payables 3,324 14,652  
Solaseado Solar Power Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 2,890 66 0
Electricity purchase 31,031 28,516 0
Chungsongmeon BongSan wind power Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 1 0 0
Energyco Co., Ltd. (formerly, Energyco LLC)      
Disclosure of transactions between related parties [line items]      
Electricity sales 1 0 0
Busan Industrial Solar Power Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 9 0 0
Omisan Wind Power Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity sales 1 0 0
Electricity purchase 7 0 0
Thirty five Joint ventures (Overseas)      
Disclosure of transactions between related parties [line items]      
Electricity sales and others 773,289 831,596 1,275,279
KW Nuclear Components Co., Ltd      
Disclosure of transactions between related parties [line items]      
Service sales 96 0 0
Samsu Wind Power Co., Ltd.      
Disclosure of transactions between related parties [line items]      
Electricity purchase 2,800 0 0
Outstanding balances for related party transactions [abstract]      
Trade payables 1,300    
Five Joint ventures (Overseas)      
Disclosure of transactions between related parties [line items]      
Electricity purchase and Others 49,055 14,767 7,232
Eighteen Joint ventures (Overseas)      
Outstanding balances for related party transactions [abstract]      
Trade receivables 84,150 58,839  
Non-trade receivables and others 26,060 17,217  
Non-trade payables and others 22,050 105,682  
Korea Development Bank      
Disclosure of transactions between related parties [line items]      
Electricity sales 4,177 4,248 3,948
Dividend paid 256,862 17 20
Interest income 756 3,461 2,091
Interest expense 2,756 3,872 ₩ 4,063
Outstanding balances for related party transactions [abstract]      
Non-trade receivables and others 420,732 206,916  
Non-trade payables and others 21,172 123  
Accrued interest income 154 51  
Derivative assets ₩ 59,139 20,167  
Derivative liabilities   ₩ 20,001