| Disclosure of fee and commission income | During the three months and the nine months ended December 31, 2024, and December 31, 2023, fee and commission income comprised:  
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
|  | Three months ended December 31, 2024 |  
|  | Brokerage |  | Banking |  | Insurance |  | Other |  | Total |  
|  |  |  |  |  |  |  |  |  |  |  
| Brokerage services | $ | 118,841 |  |  | $ | — |  |  | $ | — |  |  |  |  | $ | 118,841 |  |  
| Bank services | — |  |  | 8,360 |  |  | — |  |  |  |  | 8,360 |  |  
| Commission income from payment processing | — |  |  | — |  |  | — |  |  | 7,137 |  |  | 7,137 |  |  
| Underwriting and market-making services | 1,549 |  |  | — |  |  | — |  |  |  |  | 1,549 |  |  
| Other fee and commission income | 310 |  |  | 238 |  |  | — |  |  | 7,001 |  |  | 7,549 |  |  
| Total fee and commission income | $ | 120,700 |  |  | $ | 8,598 |  |  | $ | — |  |  | $ | 14,138 |  |  | $ | 143,436 |  | 
 
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
|  | Three months ended December 31, 2023 |  
|  | Brokerage |  | Banking |  | Insurance |  | Other |  | Total |  
|  |  |  |  |  |  |  |  |  |  |  
| Brokerage service | $ | 99,813 |  |  | $ | — |  |  | $ | — |  |  | $ | — |  |  | $ | 99,813 |  |  
| Commission income from payment processing | — |  |  | — |  |  | — |  |  | 8,977 |  |  | 8,977 |  |  
| Underwriting and market-making services | 3,344 |  |  | — |  |  | — |  |  | — |  |  | 3,344 |  |  
| Bank services | — |  |  | 1,331 |  |  | — |  |  | — |  |  | 1,331 |  |  
| Other fee and commission income | 249 |  |  | 171 |  |  | 38 |  |  | 6,236 |  |  | 6,694 |  |  
| Total fee and commission income | $ | 103,406 |  |  | $ | 1,502 |  |  | $ | 38 |  |  | $ | 15,213 |  |  | $ | 120,159 |  | 
 
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
|  | Nine months ended December 31, 2024 |  
|  | Brokerage |  | Banking |  | Insurance |  | Other |  | Total |  
|  |  |  |  |  |  |  |  |  |  |  
| Brokerage services | $ | 319,386 |  |  | $ | — |  |  | $ | — |  |  | $ | — |  |  | $ | 319,386 |  |  
| Commission income from payment processing | — |  |  | — |  |  | — |  |  | 21,670 |  |  | 21,670 |  |  
| Bank services | — |  |  | 12,748 |  |  | — |  |  | — |  |  | 12,748 |  |  
| Underwriting and market-making services | 7,465 |  |  | — |  |  | — |  |  | — |  |  | 7,465 |  |  
| Other fee and commission income | 432 |  |  | 844 |  |  | 147 |  |  | 17,284 |  |  | 18,707 |  |  
| Total fee and commission income | $ | 327,283 |  |  | $ | 13,592 |  |  | $ | 147 |  |  | $ | 38,954 |  |  | $ | 379,976 |  |  
|  |  |  |  |  |  |  |  |  |  | 
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
|  | Nine months ended December 31, 2023 |  
|  | Brokerage |  | Banking |  | Insurance |  | Other |  | Total |  
|  |  |  |  |  |  |  |  |  |  |  
| Brokerage services | $ | 239,608 |  |  | $ | — |  |  | $ | — |  |  | $ | — |  |  | $ | 239,608 |  |  
| Commission income from payment processing | — |  |  | — |  |  | — |  |  | 37,318 |  |  | 37,318 |  |  
| Bank services | — |  |  | 23,480 |  |  | — |  |  | — |  |  | 23,480 |  |  
| Underwriting and market-making services | 15,085 |  |  | — |  |  | — |  |  | — |  |  | 15,085 |  |  
| Other fee and commission income | 359 |  |  | 714 |  |  | 82 |  |  | 13,919 |  |  | 15,074 |  |  
| Total fee and commission income | $ | 255,052 |  |  | $ | 24,194 |  |  | $ | 82 |  |  | $ | 51,237 |  |  | $ | 330,565 |  |  |