| Disclosure of fee and commission income | During the three months and the six months ended September 30, 2024, and September 30, 2023, fee and commission income comprised:  
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
|  | Three months ended September 30, 2024 |  
|  | Brokerage |  | Banking |  | Insurance |  | Other |  | Total |  
|  |  |  |  |  |  |  |  |  |  |  
| Brokerage services | $ | 107,378 |  |  | $ | — |  |  | $ | — |  |  | $ | — |  |  | $ | 107,378 |  |  
| Commission income from payment processing | — |  |  | — |  |  | — |  |  | 5,970 |  |  | 5,970 |  |  
| Bank services | — |  |  | 1,872 |  |  | — |  |  | — |  |  | 1,872 |  |  
| Underwriting and market-making services | 1,214 |  |  | — |  |  | — |  |  | — |  |  | 1,214 |  |  
| Other fee and commission income | 48 |  |  | 326 |  |  | 32 |  |  | 4,211 |  |  | 4,617 |  |  
| Total fee and commission income | $ | 108,640 |  |  | $ | 2,198 |  |  | $ | 32 |  |  | $ | 10,181 |  |  | $ | 121,051 |  | 
 
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
|  | Three months ended September 30, 2023 |  
|  | Brokerage |  | Banking |  | Insurance |  | Other |  | Total |  
|  |  |  |  |  |  |  |  |  |  |  
| Brokerage service | $ | 84,713 |  |  | $ | — |  |  | $ | — |  |  | $ | — |  |  | $ | 84,713 |  |  
| Commission income from payment processing | — |  |  | — |  |  | — |  |  | 10,299 |  |  | 10,299 |  |  
| Bank services | — |  |  | 9,308 |  |  | — |  |  | — |  |  | 9,308 |  |  
| Underwriting and market-making services | 2,910 |  |  | — |  |  | — |  |  | — |  |  | 2,910 |  |  
| Other fee and commission income | 51 |  |  | 218 |  |  | 2 |  |  | 4,202 |  |  | 4,473 |  |  
| Total fee and commission income | $ | 87,674 |  |  | $ | 9,526 |  |  | $ | 2 |  |  | $ | 14,501 |  |  | $ | 111,703 |  | 
 
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
|  | Six months ended September 30, 2024 |  
|  | Brokerage |  | Banking |  | Insurance |  | Other |  | Total |  
|  |  |  |  |  |  |  |  |  |  |  
| Brokerage services | $ | 200,545 |  |  | $ | — |  |  | $ | — |  |  | $ | — |  |  | $ | 200,545 |  |  
| Commission income from payment processing | — |  |  | — |  |  | — |  |  | 14,533 |  |  | 14,533 |  |  
| Underwriting and market-making services | 5,916 |  |  | — |  |  | — |  |  | — |  |  | 5,916 |  |  
| Bank services | — |  |  | 4,388 |  |  | — |  |  | — |  |  | 4,388 |  |  
| Other fee and commission income | 122 |  |  | 606 |  |  | 147 |  |  | 10,283 |  |  | 11,158 |  |  
| Total fee and commission income | $ | 206,583 |  |  | $ | 4,994 |  |  | $ | 147 |  |  | $ | 24,816 |  |  | $ | 236,540 |  |  
|  |  |  |  |  |  |  |  |  |  | 
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
|  | Six months ended September 30, 2023 |  
|  | Brokerage |  | Banking |  | Insurance |  | Other |  | Total |  
|  |  |  |  |  |  |  |  |  |  |  
| Brokerage services | $ | 139,795 |  |  | $ | — |  |  | $ | — |  |  | $ | — |  |  | $ | 139,795 |  |  
| Commission income from payment processing | — |  |  | — |  |  | — |  |  | 28,341 |  |  | 28,341 |  |  
| Bank services | — |  |  | 22,149 |  |  | — |  |  | — |  |  | 22,149 |  |  
| Underwriting and market-making services | 11,741 |  |  | — |  |  | — |  |  | — |  |  | 11,741 |  |  
| Other fee and commission income | 110 |  |  | 543 |  |  | 44 |  |  | 7,683 |  |  | 8,380 |  |  
| Total fee and commission income | $ | 151,646 |  |  | $ | 22,692 |  |  | $ | 44 |  |  | $ | 36,024 |  |  | $ | 210,406 |  |  |