| NET INTEREST INCOME/EXPENSE | NET INTEREST INCOME/EXPENSE Net interest income/expense for the three months ended September 30, 2023, and September 30, 2022 includes: 
 
|  |  |  |  |  |  |  |  |  |  |  |  |  
|  | Three months ended September 30, 2023 |  | Three months ended September 30, 2022 |  
| Interest income: |  |  |  |  
| Interest income on trading securities | $ | 114,039 |  |  | $ | 33,787 |  |  
| Interest income on loans to customers | 42,868 |  |  | 7,203 |  |  
| Interest income on margin loans to customers | 42,573 |  |  | 9,966 |  |  
| Interest income on securities available-for-sale | 9,653 |  |  | 6,553 |  |  
| Interest income on reverse repurchase agreements and amounts due from banks | 3,930 |  |  | 1,349 |  |  
| Other interest income | — |  |  | 141 |  |  
| Total interest income | $ | 213,063 |  |  | $ | 58,999 |  |  
|  |  |  |  |  
| Interest expense: |  |  |  |  
| Interest expense on securities repurchase agreement obligations | $ | 117,009 |  |  | $ | 32,328 |  |  
| Interest expense on customer accounts and deposits | 17,864 |  |  | 7,569 |  |  
| Interest expense on margin lending payable | 3,467 |  |  | — |  |  
| Interest expense on debt securities issued | 961 |  |  | 848 |  |  
| Interest expense on loans received | 26 |  |  | 118 |  |  
| Other interest expense | 54 |  |  | — |  |  
| Total interest expense | $ | 139,381 |  |  | $ | 40,863 |  |  
|  |  |  |  |  
| Net interest income | $ | 73,682 |  |  | $ | 18,136 |  | Net interest income/expense for the six months ended September 30, 2023, and September 30, 2022 includes: 
|  |  |  |  |  |  |  |  |  |  |  |  |  
|  | Six months ended September 30, 2023 |  | Six months ended September 30, 2022 |  
| Interest income: |  |  |  |  
| Interest income on trading securities | $ | 200,880 |  |  | $ | 65,302 |  |  
| Interest income on loans to customers | 74,201 |  |  | 14,880 |  |  
| Interest income on margin loans to customers | 59,753 |  |  | 11,830 |  |  
| Interest income on securities available-for-sale | 17,997 |  |  | 13,231 |  |  
| Interest income on reverse repurchase agreements and amounts due from banks | 6,987 |  |  | 2,136 |  |  
| Other interest income | 2,594 |  |  | 183 |  |  
| Total interest income | $ | 362,412 |  |  | $ | 107,562 |  |  
|  |  |  |  |  
| Interest expense: |  |  |  |  
| Interest expense on securities repurchase agreement obligations | $ | 192,464 |  |  | $ | 65,508 |  |  
| Interest expense on customer accounts and deposits | 33,467 |  |  | 13,633 |  |  
| Interest expense on margin lending payable | 6,460 |  |  | — |  |  
| Interest expense on debt securities issued | 1,896 |  |  | 1,615 |  |  
| Interest expense on loans received | 53 |  |  | 178 |  |  
| Other interest expense | 87 |  |  | — |  |  
| Total interest expense | $ | 234,427 |  |  | $ | 80,934 |  |  
|  |  |  |  |  
| Net interest income | $ | 127,985 |  |  | $ | 26,628 |  |  |