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Related Party Transactions - Details Of Significant Profit Or Loss Arising From Transactions With Related Parties (Details) - KRW (₩)
₩ in Millions
 12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Balhae Infrastructure Company      
Related party transactions [abstract]      
Fee and commission income ₩ 5,101 ₩ 5,194 ₩ 5,689
Outstanding balances for related party transactions [abstract]      
Other assets 1,304 1,306  
Incheon Bridge Co., Ltd.      
Related party transactions [abstract]      
Interest income 10,420 7,516 4,069
Interest expense 979 517 158
Fee and commission income 28 23 22
Fee and commission expense 7 6 6
Insurance income 219 212 230
Gains on financial instruments at fair value through profit or loss 334 0 0
Losses on financial instruments at fair value through profit or loss 0 4,434 1,374
Reversal of credit losses 0 28 444
Provision for credit losses 54 9 1
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 33,282 32,948  
Loans measured at amortized cost (gross amount) 80,512 95,211  
Allowances for credit losses 38 12  
Other assets 528 615  
Deposits 40,992 48,639  
Provisions 45 18  
Insurance liabilities 87 89  
Other liabilities 504 446  
Jungdo Co., Ltd.      
Outstanding balances for related party transactions [abstract]      
Deposits 4 4  
KB GwS Private Securities Investment Trust      
Related party transactions [abstract]      
Fee and commission income ₩ 0 0 146
Outstanding balances for related party transactions [abstract]      
Description of transactions with related party Excluded from the Group’s related party as of December 31, 2023.    
Korea Credit Bureau Co., Ltd.      
Related party transactions [abstract]      
Interest expense ₩ 1 1 6
Fee and commission income 776 649 910
Fee and commission expense 8,444 3,973 4,256
Insurance income 3 4 4
Other operating expenses 15 15 11
Provision for credit losses 1 0 0
Outstanding balances for related party transactions [abstract]      
Loans measured at amortized cost (gross amount) 37 38  
Deposits 17,003 27,889  
Provisions 2 2  
Insurance liabilities ₩ 1 1  
Description of transactions with related party the Group recognized ￦ 58,304 million in non-operating income for the year ended December 31, 2023, which was confirmed in the lawsuit for damage against Korea Credit Bureau Co., Ltd.    
KB Star Office Private Real Estate Master Fund No. 1      
Related party transactions [abstract]      
Interest income ₩ 0 0 370
Interest expense 0 2 5
Fee and commission income ₩ 0 276 435
Outstanding balances for related party transactions [abstract]      
Description of transactions with related party Excluded from the Group’s related party as of December 31, 2023.    
Kendai Co.,Ltd.      
Related party transactions [abstract]      
Other non-operating expense ₩ 0 3 0
Taeyoungjungkong Co., Ltd      
Related party transactions [abstract]      
Interest income 2 0 0
Aju Good Technology Venture Fund      
Related party transactions [abstract]      
Interest expense 111 108 27
Outstanding balances for related party transactions [abstract]      
Deposits 1,202 7,222  
Other liabilities 1 73  
KG Capital Co., Ltd.      
Related party transactions [abstract]      
Interest income 293 889 941
Fee and commission income 18 47 88
Fee and commission expense 1 10 15
Insurance income 13 43 42
Other operating income 0 487 710
Other operating expenses 11 32 64
Reversal of credit losses 55 0 11
Provision for credit losses 0 9 0
Outstanding balances for related party transactions [abstract]      
Loans measured at amortized cost (gross amount) [1] 0 40,040  
Allowances for credit losses [1] 0 55  
Other assets [1] 0 63  
Deposits [1] 0 10  
Insurance liabilities [1] 0 14  
Other liabilities [1] ₩ 0 5  
Description of transactions with related party Excluded from the Group’s related party as of December 31, 2023, therefore, the remaining outstanding balances with those entities are not disclosed.    
Star-Lord General Investors Private Real Estate Investment Company No.10      
Related party transactions [abstract]      
Interest income ₩ 5,934 3,098 0
Interest expense 543 413 0
Fee and commission income 20 0 0
Insurance income 137 97 0
Provision for credit losses 4 1 0
General and administrative expenses 9,720 5,562 0
Outstanding balances for related party transactions [abstract]      
Loans measured at amortized cost (gross amount) 149,590 149,294  
Allowances for credit losses 5 1  
Other assets 8,689 8,591  
Insurance liabilities 44 46  
Other liabilities 8,245 14,227  
Property and equipment 5,615 9,915  
KB-Brain KOSDAQ Scale-up New Technology Business Investment Fund      
Related party transactions [abstract]      
Interest expense 4 6 17
Fee and commission income 209 423 514
Outstanding balances for related party transactions [abstract]      
Deposits 0 1,526  
Other liabilities ₩ 0 1  
KG Capital Co., Ltd      
Outstanding balances for related party transactions [abstract]      
Description of transactions with related party the Group purchased installment financial assets, etc. from KG Capital Co., Ltd. amounting to ￦ 486,586 million and ￦ 373,044 million for the years ended December 31, 2022 and 2023, respectively.    
Food Factory Co., Ltd.      
Related party transactions [abstract]      
Interest income ₩ 62 80 70
Interest expense 1 6 5
Fee and commission income 0 1 0
Fee and commission expense 0 0 2
Insurance income 9 10 9
Gains on financial instruments at fair value through profit or loss 43 33 0
Losses on financial instruments at fair value through profit or loss 0 0 1
Reversal of credit losses 2 1 6
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 738 696  
Loans measured at amortized cost (gross amount) 2,137 3,345  
Allowances for credit losses 2 4  
Other assets 5 4  
Deposits 629 664  
Insurance liabilities 2 8  
Other liabilities 1 1  
KB Pre IPO Secondary Venture Fund No.1      
Related party transactions [abstract]      
Interest expense 0 0 1
Fee and commission income 0 1,204 110
Acts Co., Ltd.      
Related party transactions [abstract]      
Insurance income ₩ 0 2 1
Outstanding balances for related party transactions [abstract]      
Description of transactions with related party Excluded from the Group’s related party as of December 31, 2023.    
Dongjo Co., Ltd.      
Related party transactions [abstract]      
Interest income ₩ 36 9 0
Insurance income 0 0 1
POSCO-KB Shipbuilding Fund      
Related party transactions [abstract]      
Fee and commission income (99) 177 213
Outstanding balances for related party transactions [abstract]      
Other assets 678 177  
Dae-A Leisure Co., Ltd.      
Related party transactions [abstract]      
Interest expense 0 0 2
Outstanding balances for related party transactions [abstract]      
Deposits 150 154  
Paycoms Co., Ltd.      
Related party transactions [abstract]      
Interest income 154 7 10
Gains on financial instruments at fair value through profit or loss 0 39 42
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss [1] 0 1,172  
Deposits [1] ₩ 0 1  
Description of transactions with related party Excluded from the Group’s related party as of December 31, 2023, therefore, the remaining outstanding balances with those entities are not disclosed.    
Big Dipper Co., Ltd.      
Related party transactions [abstract]      
Interest expense ₩ 0 1 0
Fee and commission expense 266 393 655
Outstanding balances for related party transactions [abstract]      
Loans measured at amortized cost (gross amount) 14 18  
Deposits 40 19  
Other liabilities 8 0  
KB-KDBC Pre-IPO New Technology Business Investment Fund      
Related party transactions [abstract]      
Interest expense 0 1 1
Fee and commission income 0 129 190
Outstanding balances for related party transactions [abstract]      
Deposits 46 317  
KB-TS Technology Venture Private Equity Fund      
Related party transactions [abstract]      
Fee and commission income 324 185 285
KB-SJ Tourism Venture Fund      
Related party transactions [abstract]      
Fee and commission income 312 209 279
Banksalad Co., Ltd.      
Related party transactions [abstract]      
Fee and commission income 37 36 36
Fee and commission expense 11 17 48
Gains on financial instruments at fair value through profit or loss 0 0 613
Losses on financial instruments at fair value through profit or loss 0 0 663
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 9,148 10,470  
Iwon Alloy Co., Ltd.      
Related party transactions [abstract]      
Insurance income 1 1 0
Outstanding balances for related party transactions [abstract]      
Deposits 1 1  
Insurance liabilities 0 1  
Computerlife Co      
Outstanding balances for related party transactions [abstract]      
Deposits 0 3  
Bioprotect Ltd.      
Related party transactions [abstract]      
Gains on financial instruments at fair value through profit or loss 0 0 293
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 4,474 3,802  
RMGP Bio-Pharma Investment Fund, L.P.      
Related party transactions [abstract]      
Fee and commission income 40 43 38
Gains on financial instruments at fair value through profit or loss 0 0 531
Losses on financial instruments at fair value through profit or loss 0 0 2,373
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 5,938 6,384  
Other liabilities 62 36  
RMGP Bio-Pharma Investment, L.P.      
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 20 17  
KB-MDI Centauri Fund L.P.      
Related party transactions [abstract]      
Fee and commission income 491 487 401
Gains on financial instruments at fair value through profit or loss 0 0 551
Losses on financial instruments at fair value through profit or loss 0 0 284
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 18,993 17,471  
Other assets 221 470  
Checkmate Therapeutics Inc.      
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 3,200 3,200  
Insurance liabilities 0 3  
G1 Playground Co., Ltd.      
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 0 1,000  
Hibiscus Fund L.P.      
Related party transactions [abstract]      
Fee and commission income 928 524 372
Gains on financial instruments at fair value through profit or loss 0 0 113
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 12,915 10,221  
Other assets 258 0  
Other liabilities 0 257  
RMG-KB BioAccess Fund L.P.      
Related party transactions [abstract]      
Fee and commission income 326 325 57
Gains on financial instruments at fair value through profit or loss 0 0 5
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 5,036 2,753  
RMG-KB BP Management Ltd.      
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 174 77  
Spoon Radio Co., Ltd      
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 19,506 0  
Neuroptika Inc.      
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 5,879 0  
Bitgoeul Cheomdan Green 1st Co., Ltd.      
Outstanding balances for related party transactions [abstract]      
Deposits 833 0  
S&E Bio Co., Ltd.      
Related party transactions [abstract]      
Interest expense 43 2 1
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 4,000 4,000  
Loans measured at amortized cost (gross amount) 13 10  
Deposits 2,342 6,419  
Other liabilities 13 0  
Contents First Inc.      
Related party transactions [abstract]      
Interest income 346 128 0
Interest expense 73 34 83
Fee and commission income 2 1 0
Provision for credit losses 8 1 0
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 7,277 7,277  
Loans measured at amortized cost (gross amount) 10,365 10,017  
Allowances for credit losses 7 1  
Other assets 4 2  
Deposits 1,072 5,010  
Provisions 1 0  
Other liabilities 6 21  
December & Company Inc.      
Related party transactions [abstract]      
Insurance income 187 174 109
Outstanding balances for related party transactions [abstract]      
Deposits [1] 0 1  
Insurance liabilities [1] ₩ 0 9  
Description of transactions with related party Excluded from the Group’s related party as of December 31, 2023, therefore, the remaining outstanding balances with those entities are not disclosed.    
GENINUS Inc.      
Related party transactions [abstract]      
Interest expense ₩ 0 12 29
Gains on financial instruments at fair value through profit or loss 0 0 4,009
Provision for credit losses ₩ 0 0 6
Outstanding balances for related party transactions [abstract]      
Description of transactions with related party Excluded from the Group’s related party as of December 31, 2023.    
Pin Therapeutics Inc.      
Related party transactions [abstract]      
Interest expense ₩ 101 110 0
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 5,000 5,000  
Loans measured at amortized cost (gross amount) 11 13  
Deposits 265 6,033  
Other liabilities 0 18  
IMBiologics Corp.      
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 7,000 5,000  
Loans measured at amortized cost (gross amount) 5 4  
Wyatt Co., Ltd.      
Related party transactions [abstract]      
Insurance income 102 142 87
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 6,000 6,000  
Deposits 1 1  
Insurance liabilities 73 75  
Skydigital Inc.      
Related party transactions [abstract]      
Fee and commission income 3 3 3
Outstanding balances for related party transactions [abstract]      
Deposits 65 10  
Il-Kwang Electronic Materials Co., Ltd      
Related party transactions [abstract]      
Other non-operating expense 0 1 0
KB No. 17 Special Purpose Acquisition Company      
Related party transactions [abstract]      
Interest expense 0 1 14
Losses on financial instruments at fair value through profit or loss ₩ 0 0 1,388
Outstanding balances for related party transactions [abstract]      
Description of transactions with related party Excluded from the Group’s related party as of December 31, 2023.    
SO-MYUNG Recycling Co., Ltd.      
Related party transactions [abstract]      
Other non-operating expense ₩ 0 2 0
KB No.18 Special Purpose Acquisition Company      
Related party transactions [abstract]      
Interest expense 0 5 20
Gains on financial instruments at fair value through profit or loss ₩ 0 0 8
Outstanding balances for related party transactions [abstract]      
Description of transactions with related party Excluded from the Group’s related party as of December 31, 2023.    
KB No.19 Special Purpose Acquisition Company      
Related party transactions [abstract]      
Interest expense ₩ 0 5 9
Gains on financial instruments at fair value through profit or loss ₩ 0 0 36
Outstanding balances for related party transactions [abstract]      
Description of transactions with related party Excluded from the Group’s related party as of December 31, 2023.    
KB No.20 Special Purpose Acquisition Company      
Related party transactions [abstract]      
Interest expense ₩ 0 22 15
Gains on financial instruments at fair value through profit or loss ₩ 0 0 68
Outstanding balances for related party transactions [abstract]      
Description of transactions with related party Excluded from the Group’s related party as of December 31, 2023.    
KB No.21 Special Purpose Acquisition Company      
Related party transactions [abstract]      
Interest expense ₩ 68 30 0
Fee and commission income 0 263 0
Gains on financial instruments at fair value through profit or loss 28 1,469 0
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 2,987 2,959  
Deposits 2,261 2,263  
Other liabilities 38 29  
KB No.22 Special Purpose Acquisition Company      
Related party transactions [abstract]      
Interest expense 2 1 0
Fee and commission income 0 175 0
Gains on financial instruments at fair value through profit or loss 1,013 982 0
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 2,985 1,972  
Deposits 1,848 1,948  
KB No.23 Special Purpose Acquisition Company      
Related party transactions [abstract]      
Interest expense 46 23 0
Gains on financial instruments at fair value through profit or loss 0 1,476 0
Losses on financial instruments at fair value through profit or loss 1,483 0 0
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss [1] 1,489 2,971  
Deposits [1] 0 2,205  
Other liabilities [1] ₩ 0 22  
Description of transactions with related party Excluded from the Group’s related party as of December 31, 2023, therefore, the remaining outstanding balances with those entities are not disclosed.    
KB No.24 Special Purpose Acquisition Company      
Related party transactions [abstract]      
Interest expense ₩ 7 1 0
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss [1] 0 6,975  
Deposits [1] 0 9,983  
Other liabilities [1] ₩ 0 1  
Description of transactions with related party Excluded from the Group’s related party as of December 31, 2023, therefore, the remaining outstanding balances with those entities are not disclosed.    
KB No.25 Special Purpose Acquisition Company      
Related party transactions [abstract]      
Interest expense ₩ 39 0 0
Gains on financial instruments at fair value through profit or loss 1,130 0 0
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 2,025 0  
Deposits 1,586 0  
Other liabilities 39 0  
KB No.26 Special Purpose Acquisition Company      
Related party transactions [abstract]      
Interest expense 38 0 0
Gains on financial instruments at fair value through profit or loss 1,209 0 0
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 2,204 0  
Deposits 1,761 0  
Other liabilities 37 0  
KB No.27 Special Purpose Acquisition Company      
Related party transactions [abstract]      
Interest expense 65 0 0
Gains on financial instruments at fair value through profit or loss 3,059 0 0
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 6,054 0  
Deposits 4,497 0  
Other liabilities 65 0  
KB SPROTT Renewable Private Equity Fund No.1      
Related party transactions [abstract]      
Fee and commission income 320 345 487
KB-Stonebridge Secondary Private Equity Fund      
Related party transactions [abstract]      
Fee and commission income 582 706 550
Other operating income 113 0 0
COSES GT      
Related party transactions [abstract]      
Interest income 30 23 18
Interest expense 0 1 1
Losses on financial instruments at fair value through profit or loss 4,910 0 0
Reversal of credit losses 5 0 3
Provision for credit losses 0 3 0
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 0 4,930  
Loans measured at amortized cost (gross amount) 1 506  
Allowances for credit losses 0 4  
Other assets 0 2  
Deposits 1 1,213  
IDTECK Co., Ltd      
Related party transactions [abstract]      
Insurance income 0 0 1
TeamSparta Inc.      
Related party transactions [abstract]      
Interest expense 212 19 0
Fee and commission income 11 0 0
Provision for credit losses 2 0 0
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 4,001 4,001  
Loans measured at amortized cost (gross amount) 307 0  
Allowances for credit losses 1 0  
Deposits 7,672 12,502  
Provisions 1 0  
Other liabilities 62 6  
Mantisco Co., Ltd.      
Related party transactions [abstract]      
Interest expense 0 1 1
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 3,000 3,000  
Loans measured at amortized cost (gross amount) 13 15  
Deposits 46 623  
SuperNGine Co., Ltd.      
Related party transactions [abstract]      
Interest income 25 0 0
Interest expense 0 0 1
Fee and commission income 1 0 0
Provision for credit losses 6 0 0
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 1,996 1,996  
Loans measured at amortized cost (gross amount) 603 6  
Allowances for credit losses 6 0  
Other assets 1 0  
Deposits 69 17  
Desilo Inc.      
Related party transactions [abstract]      
Interest income 13 9 1
Provision for credit losses 3 0 2
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 3,168 3,168  
Loans measured at amortized cost (gross amount) 300 300  
Allowances for credit losses 5 2  
Deposits 3 1  
Turing Co Ltd [Member]      
Related party transactions [abstract]      
Interest income 24 0 0
Interest expense 7 1 1
Provision for credit losses 14 0 0
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 3,000 3,000  
Loans measured at amortized cost (gross amount) 1,901 0  
Allowances for credit losses 14 0  
Other assets 11 0  
Deposits 1,726 2,788  
Other liabilities 6 0  
IGGYMOB Co Ltd [Member]      
Related party transactions [abstract]      
Interest expense 0 1 1
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 5,000 5,000  
Loans measured at amortized cost (gross amount) 7 15  
Deposits 0 254  
Kukka Co., Ltd.      
Related party transactions [abstract]      
Interest expense 0 2 0
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 2,490 2,490  
ZIPDOC Inc.      
Related party transactions [abstract]      
Interest expense 0 1 0
Reversal of credit losses 0 3 0
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 2,000 2,000  
Deposits 181 915  
Grinergy Co., Ltd.      
Related party transactions [abstract]      
Interest expense 1 0 0
Provision for credit losses 1 0 0
Chabot Mobility Co., Ltd.      
Related party transactions [abstract]      
Interest expense 0 1 0
Fee and commission expense 2,154 824 0
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 2,000 2,000  
Deposits 164 86  
Wemade Connect Co., Ltd.      
Related party transactions [abstract]      
Interest income 2 3 0
Interest expense 316 81 0
Reversal of credit losses 0 1 0
Provision for credit losses 9 0 0
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 12,293 12,000  
Loans measured at amortized cost (gross amount) 44 52  
Allowances for credit losses 6 0  
Deposits 8,843 10,370  
Provisions 8 2  
Insurance liabilities 1 2  
Other liabilities 53 28  
TMAP Mobility Co., Ltd.      
Related party transactions [abstract]      
Interest expense 1,460 226 0
Fee and commission income 2 0 0
Fee and commission expense 998 78 0
Insurance income 209 0 0
Reversal of credit losses 9 0 0
Outstanding balances for related party transactions [abstract]      
Loans measured at amortized cost (gross amount) 106 0  
Allowances for credit losses 1 0  
Deposits 80,016 30,000  
Provisions 2 0  
Other liabilities 763 76  
FutureConnect Co., Ltd.      
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 1,499 1,499  
Gushcloud Talent Agency      
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 3,688 4,165  
NexThera Co., Ltd.      
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 3,000 2,000  
Nextrade Co., Ltd.      
Related party transactions [abstract]      
Interest expense 2,911 263 0
Outstanding balances for related party transactions [abstract]      
Deposits 56,203 56,202  
Other liabilities 3,174 263  
WJ Private Equity Fund No.1      
Related party transactions [abstract]      
Fee and commission income 7 7 7
Outstanding balances for related party transactions [abstract]      
Other assets 2 2  
Deposits 103 221  
UPRISE, Inc.      
Related party transactions [abstract]      
Interest income 0 0 5
Interest expense 0 3 1
Reversal of credit losses 0 0 1
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 5,710 5,248  
Deposits 0 27  
Stratio, Inc.      
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 1,000 1,000  
Honest Fund, Inc.      
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 3,999 3,999  
CellinCells Co., Ltd.      
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 2,000 2,000  
Loans measured at amortized cost (gross amount) 3 7  
Deposits 37 37  
Channel Corporation      
Related party transactions [abstract]      
Interest expense 67 43 0
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 16,906 18,099  
Deposits 2,030 3,000  
Other liabilities 11 21  
CWhy Inc.      
Related party transactions [abstract]      
Insurance income 2 2 0
Bomapp Inc.      
Related party transactions [abstract]      
Fee and commission expense 0 0 5
Losses on financial instruments at fair value through profit or loss 0 0 1,980
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss [1] ₩ 0 1  
Description of transactions with related party Excluded from the Group’s related party as of December 31, 2023, therefore, the remaining outstanding balances with those entities are not disclosed.    
MitoImmune Therapeutics      
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss ₩ 7,000 7,000  
KB Social Impact Investment Fund      
Related party transactions [abstract]      
Fee and commission income 284 286 300
Outstanding balances for related party transactions [abstract]      
Other assets 260 436  
KB-UTC Inno-Tech Venture Fund      
Related party transactions [abstract]      
Fee and commission income 431 449 471
Other operating income 3 0 0
KBSP Private Equity Fund No.4      
Related party transactions [abstract]      
Fee and commission income 0 211 389
KB-NAU Special Situation Corporate Restructuring Private Equity Fund      
Related party transactions [abstract]      
Fee and commission income 1,052 561 1,198
2020 KB Fintech Renaissance Fund      
Related party transactions [abstract]      
Fee and commission income 147 147 147
Outstanding balances for related party transactions [abstract]      
Other assets 37 37  
OKXE Inc.      
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 800 800  
KB Material and Parts No.1 PEF      
Related party transactions [abstract]      
Fee and commission income 705 353 353
Other operating income 34 0 0
FineKB Private Equity Fund No.1      
Related party transactions [abstract]      
Fee and commission income 378 641 540
Gains on financial instruments at fair value through profit or loss 16 0 0
Outstanding balances for related party transactions [abstract]      
Other assets 13 160  
Paramark KB Fund No.1      
Related party transactions [abstract]      
Fee and commission income 129 356 100
Outstanding balances for related party transactions [abstract]      
Other liabilities 34 34  
KB-Badgers Future Mobility ESG Fund No.1      
Related party transactions [abstract]      
Fee and commission income 1,300 905 0
KB Bio Private Equity No.3 Ltd.      
Related party transactions [abstract]      
Fee and commission income 0 4,035 324
K The 15th REIT Co., Ltd.      
Related party transactions [abstract]      
Fee and commission income 0 0 500
Insurance income ₩ 0 0 1
Outstanding balances for related party transactions [abstract]      
Description of transactions with related party Excluded from the Group’s related party as of December 31, 2023.    
KB-KTB Technology Venture Fund      
Related party transactions [abstract]      
Fee and commission income ₩ 669 600 0
THE CHAEUL FUND NO.1      
Related party transactions [abstract]      
Fee and commission income 0 82 0
Bluepointpartners Inc.      
Related party transactions [abstract]      
Gains on financial instruments at fair value through profit or loss 0 0 846
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 1,874 2,133  
KB-Solidus Global Healthcare Fund      
Related party transactions [abstract]      
Fee and commission income 284 350 167
Gains on financial instruments at fair value through profit or loss 8,400 0 0
Outstanding balances for related party transactions [abstract]      
Other assets 284 350  
SwatchOn Inc.      
Related party transactions [abstract]      
Interest expense 0 5 10
Fee and commission income ₩ 0 5 8
Outstanding balances for related party transactions [abstract]      
Description of transactions with related party Excluded from the Group’s related party as of December 31, 2023.    
Gomi corporation Inc.      
Related party transactions [abstract]      
Interest income ₩ 88 61 19
Interest expense 0 2 1
Fee and commission income 1 1 0
Insurance income 1 0 0
Provision for credit losses 49 3 13
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 4,000 4,000  
Loans measured at amortized cost (gross amount) 2,155 2,234  
Allowances for credit losses 62 17  
Other assets 5 5  
Deposits 78 915  
Provisions 3 0  
Other liabilities 1 1  
Go2joy Co., Ltd.      
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 1,200 1,200  
ClavisTherapeutics, Inc.      
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 0 2,000  
4N Inc.      
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 0 200  
Deposits 49 5  
Xenohelix Co., Ltd.      
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 3,100 2,100  
Deposits 904 0  
RAND Bio Science Co., Ltd.      
Outstanding balances for related party transactions [abstract]      
Loans measured at amortized cost (gross amount) 1 0  
Deposits 4 3  
KB Cape No.1 Private Equity Fund      
Related party transactions [abstract]      
Fee and commission income 217 72 144
Losses on financial instruments at fair value through profit or loss 16 0 69
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 1,935 2,017  
Other assets 73 0  
Keystone-Hyundai Securities No. 1 Private Equity Fund      
Related party transactions [abstract]      
Fee and commission income ₩ 0 0 43
Outstanding balances for related party transactions [abstract]      
Description of transactions with related party Excluded from the Group’s related party as of December 31, 2023.    
KB-GeneN Medical Venture Fund No.1      
Related party transactions [abstract]      
Fee and commission income ₩ 89 76 0
KB-BridgePole Venture Investment Fund      
Related party transactions [abstract]      
Fee and commission income 135 118 0
Other operating income 638 0 0
KB-BridgePole Venture Investment Fund No.2      
Related party transactions [abstract]      
Fee and commission income 20 0 0
KB-Kyobo New Mobility Power Fund      
Related party transactions [abstract]      
Fee and commission income 79 69 0
KB Co-Investment Private Equity Fund No.1      
Related party transactions [abstract]      
Fee and commission income 904 483 0
Outstanding balances for related party transactions [abstract]      
Other assets 255 191  
KB-NP Green ESG New Technology Venture Capital Fund      
Related party transactions [abstract]      
Fee and commission income 1,173 435 0
KB-FT Green Growth No.1 New Technology Business Investment Association      
Related party transactions [abstract]      
Interest expense 14 0 0
Fee and commission income 135 0 0
Outstanding balances for related party transactions [abstract]      
Deposits 700 0  
Other liabilities 8 0  
KB-SUSUNG 1st Investment Fund      
Related party transactions [abstract]      
Fee and commission income 129 0 0
Youngwon Corporation      
Related party transactions [abstract]      
Insurance income ₩ 1 0 0
Outstanding balances for related party transactions [abstract]      
Description of transactions with related party Excluded from the Group’s related party as of December 31, 2023.    
Seokwang T&I Co., Ltd      
Related party transactions [abstract]      
Insurance income ₩ 1 0 0
Outstanding balances for related party transactions [abstract]      
Insurance liabilities 2 0  
3D Interactive Co., Ltd.      
Related party transactions [abstract]      
Interest expense 10 0 0
Fee and commission income 7 0 0
Provision for credit losses 2 0 0
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 2,300 0  
Loans measured at amortized cost (gross amount) 42 0  
Allowances for credit losses 2 0  
Deposits 1,501 0  
Bigwave Robotics Crop.      
Related party transactions [abstract]      
Interest income (1) 0 0
Interest expense 1 0 0
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 2,750 0  
Loans measured at amortized cost (gross amount) 31 0  
Deposits 4 0  
U-KB Credit No.1 Private Equity      
Related party transactions [abstract]      
Fee and commission income 228 0 0
KAELEEWALEE GLOBAL SAELAENJINSAMO INVESTMENT JE2HO LIMITED PARTNERSHIP      
Related party transactions [abstract]      
Interest expense 42 0 0
Outstanding balances for related party transactions [abstract]      
Deposits 3,790 0  
Other liabilities 42 0  
Blinkers Inc.      
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 999 0  
XL8 INC.      
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 5,148 0  
Elev8-Capital Fund I      
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 6,656 0  
New Daegu Busan Expressway Co., Ltd      
Outstanding balances for related party transactions [abstract]      
Loans measured at amortized cost (gross amount) 72,742 0  
Allowances for credit losses 4 0  
Other assets 57 0  
Deposits 146,169 0  
Other liabilities 1,891 0  
AIM FUTURE, Inc.      
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 2,000 0  
Loans measured at amortized cost (gross amount) 900 0  
Allowances for credit losses 2 0  
Other assets 1 0  
Deposits 3,393 0  
Other liabilities 48 0  
Novorex Inc.      
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 2,000 0  
Deposits 7 0  
Retirement pension      
Related party transactions [abstract]      
Interest expense 27 39 9
Fee and commission income 1,567 1,352 1,338
Outstanding balances for related party transactions [abstract]      
Other assets 364 778  
Other liabilities 606 10,141  
Key management personnel      
Outstanding balances for related party transactions [abstract]      
Loans measured at amortized cost (gross amount) 5,490 6,299  
Allowances for credit losses 5 3  
Other assets 7 7  
Deposits 15,902 17,618  
Provisions 2 1  
Insurance liabilities 2,293 2,374  
Other liabilities 429 387  
Spark Biopharma Inc.      
Related party transactions [abstract]      
Interest expense 468 272 ₩ 7
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 7,450 7,450  
Loans measured at amortized cost (gross amount) 17 17  
Deposits 11,419 17,534  
Other liabilities 90 91  
Grinergy      
Outstanding balances for related party transactions [abstract]      
Financial assets at fair value through profit or loss 6,486 2,500  
Provisions ₩ 1 ₩ 0  
KB Pre IPO Secondary Venture Fund No. 1      
Outstanding balances for related party transactions [abstract]      
Description of transactions with related party Excluded from the Group’s related party as of December 31, 2023.    
[1] Excluded from the Group’s related party as of December 31, 2023, therefore, the remaining outstanding balances with those entities are not disclosed.