Subclassifications Of Assets, Liabilities And Equities [Abstract]
| Concept | As at 2022-12-31 | As at 2021-12-31 | As at 2020-12-31 | 
|---|---|---|---|
| Subclassifications of assets, liabilities and equities [abstract] | |||
| Intangible assets and goodwill [abstract] | |||
| Goodwill | 
                                                5,630,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                5,630,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                5,630,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
| Investment property [abstract] | |||
| Investment property | 
                                                19,904,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                14,658,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                15,027,000
                                                
                                                    
                                                        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 | 
                                                211,005,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                293,983,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                267,652,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
| Financial assets at fair value through other comprehensive income [abstract] | |||
| Financial assets at fair value through other comprehensive income | 
                                                564,743,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                859,106,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                716,006,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
| Financial assets at amortised cost | 
                                                1,341,679,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                687,185,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                463,289,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
| Cash and cash equivalents [abstract] | |||
| Cash [abstract] | |||
| Balances with banks | 
                                                90,476,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                182,425,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                188,068,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
| Cash and cash equivalents | 
                                                2,071,158,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                2,142,718,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                2,097,672,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
| Miscellaneous assets [abstract] | |||
| Loans and advances | — | — | — | 
| Loans and advances to customers | 
                                                3,267,500,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                3,120,638,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                2,784,460,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
| Cash and bank balances at central banks | 
                                                1,983,943,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                1,963,552,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                1,912,743,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
| Reverse repurchase agreements and cash collateral on securities borrowed | 
                                                393,249,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                356,982,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                359,672,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
| Other assets | 
                                                54,252,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                52,327,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                49,404,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
| Borrowings, by type [abstract] | |||
| Bonds issued | 
                                                35,370,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                25,450,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                25,451,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
| Miscellaneous liabilities [abstract] | |||
| Deposit liabilities | — | — | — | 
| Deposits from banks | 
                                                17,673,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                52,893,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                66,052,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
| Deposits from customers [abstract] | |||
| Deposits from customers | 
                                                7,344,182,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                6,946,583,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                6,190,947,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
| Other liabilities | 
                                                67,268,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                68,112,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                61,532,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
| Issued capital [abstract] | |||
| Issued capital | 
                                                127,130,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                127,130,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                127,130,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
| Accumulated other comprehensive income [abstract] | |||
| Reserve of exchange differences on translation | 
                                                2,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                89,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                133,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
| Net assets (liabilities) [abstract] | |||
| Assets | 
                                                8,115,197,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                7,705,209,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                6,934,135,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
| Liabilities | 
                                                7,464,974,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                7,093,751,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
                                                6,344,985,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             | 
| Assets less current liabilities [abstract] |