Statement Of Cash Flows [Abstract]
| Concept | 
                                    
                                        2021-01-01 to 2021-12-31  | 
                            
                                
                                    
                                        2020-01-01 to 2020-12-31  | 
                            
                        
|---|---|---|
| Statement of cash flows [abstract] | ||
| Cash flows from (used in) operating activities [abstract] | ||
| Adjustments for dividend income | 
                                        
                                             
                                                455,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                430,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Adjustments for increase (decrease) in other liabilities | 
                                        
                                             
                                                59,506,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                5,554,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Adjustments for decrease (increase) in financial assets measured at fair value through profit or loss | — | — | 
| Adjustments for decrease (increase) in financial assets at fair value through profit or loss, mandatorily measured at fair value | — | — | 
| Adjustments for decrease (increase) in financial assets held for trading | 
                                        
                                             
                                                272,846,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                110,506,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Adjustments for decrease (increase) in loans and advances | — | — | 
| Adjustments for decrease (increase) in loans and advances to banks | 
                                        
                                             
                                                4,141,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                1,055,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Adjustments for decrease (increase) in loans and advances to customers | 
                                        
                                             
                                                558,881,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                338,605,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Adjustments for increase (decrease) in deposits | — | — | 
| Adjustments for increase (decrease) in deposits from banks | 
                                        
                                             
                                                6,051,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                745,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Adjustments for increase (decrease) in deposits from customers | 
                                        
                                             
                                                452,177,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                447,090,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Adjustments for depreciation and amortisation expense and impairment loss (reversal of impairment loss) recognised in profit or loss | 
                                        
                                             
                                                12,201,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                13,165,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Adjustments for gains (losses) on fair value adjustment, investment property | 
                                        
                                             
                                                30,340,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                2,312,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Cash flows from (used in) investing activities [abstract] | ||
| Purchase of property, plant and equipment, intangible assets other than goodwill, investment property and other non-current assets | 
                                        
                                             
                                                14,435,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                12,408,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Proceeds from disposals of property, plant and equipment, intangible assets other than goodwill, investment property and other non-current assets | 
                                        
                                             
                                                37,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                32,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Purchase of financial instruments, classified as investing activities | 
                                        
                                             
                                                116,363,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                186,581,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Cash flows from (used in) financing activities [abstract] | ||
| Proceeds from sale or issue of treasury shares | 
                                        
                                             
                                                -
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                153,017,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Proceeds from issue of ordinary shares | 
                                        
                                             
                                                -
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                39,085,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Proceeds from issue of subordinated liabilities | 
                                        
                                             
                                                53,145,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                5,688,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     |