Subclassifications Of Assets, Liabilities And Equities [Abstract]
| Concept | As at 2023-12-31 | As at 2022-12-31 | As at 2021-12-31 | 
|---|---|---|---|
| Subclassifications of assets, liabilities and equities [abstract] | |||
| Intangible assets and goodwill [abstract] | |||
| Goodwill | 
                                                5 630
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                5 630
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | — | 
| Investment property [abstract] | |||
| Investment property | 
                                                44 662
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                19 904
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | — | 
| Categories of financial assets [abstract] | |||
| Financial assets at fair value through profit or loss [abstract] | |||
| Financial assets at fair value through profit or loss | 
                                                221 397
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                211 005
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | — | 
| Financial assets at fair value through other comprehensive income [abstract] | |||
| Financial assets at fair value through other comprehensive income | 
                                                608 190
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                564 743
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | — | 
| Financial assets at amortised cost | 
                                                1 548 255
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                1 341 679
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | — | 
| Cash and cash equivalents [abstract] | |||
| Cash [abstract] | |||
| Balances with banks | 
                                                154 593
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                90 476
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | — | 
| Cash and cash equivalents | 
                                                2 174 269
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                2 071 158
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                2 142 718
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
| Miscellaneous assets [abstract] | |||
| Loans and advances | — | — | — | 
| Loans and advances to customers | 
                                                3 260 513
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                3 267 500
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | — | 
| Cash and bank balances at central banks | 
                                                2 022 320
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                1 983 943
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | — | 
| Reverse repurchase agreements and cash collateral on securities borrowed | 
                                                441 720
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                393 249
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | — | 
| Other assets | 
                                                50 793
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                54 252
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | — | 
| Borrowings, by type [abstract] | |||
| Bonds issued | 
                                                35 391
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                35 370
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | — | 
| Miscellaneous liabilities [abstract] | |||
| Deposit liabilities | — | — | — | 
| Deposits from banks | 
                                                19 756
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                17 673
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | — | 
| Deposits from customers [abstract] | |||
| Deposits from customers | 
                                                7 646 767
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                7 344 182
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | — | 
| Other liabilities | 
                                                70 734
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                67 268
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | — | 
| Issued capital [abstract] | |||
| Issued capital | 
                                                127 130
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                127 130
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | — | 
| Accumulated other comprehensive income [abstract] | |||
| Reserve of exchange differences on translation | 
                                                3,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                2,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | — | 
| Net assets (liabilities) [abstract] | |||
| Assets | 
                                                8 533 408
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                8 115 197
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | — | 
| Liabilities | 
                                                7 772 980
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                7 464 974
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | — | 
| Assets less current liabilities [abstract] |