Quarterly report [Sections 13 or 15(d)]

CUSTOMER LIABILITIES - Schedule of customer liabilities (Details)

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CUSTOMER LIABILITIES - Schedule of customer liabilities (Details) - USD ($)
$ in Thousands
 6 Months Ended 12 Months Ended
Sep. 30, 2025
Mar. 31, 2025
Revenue, Major Customer [Line Items]    
Total non-interest-bearing accounts $ 3,929,916 $ 2,582,686
Customer liabilities 5,759,636 4,304,999
Term deposits    
Revenue, Major Customer [Line Items]    
Term deposits $ 1,829,720 $ 1,722,313
Term deposits | Minimum    
Revenue, Major Customer [Line Items]    
Debt securities, interest rate during period (in percent) 0.04% 0.05%
Term deposits | Maximum    
Revenue, Major Customer [Line Items]    
Debt securities, interest rate during period (in percent) 18.45% 18.30%
Brokerage customers    
Revenue, Major Customer [Line Items]    
Total non-interest-bearing accounts $ 3,407,509 $ 2,167,111
Customer accounts    
Revenue, Major Customer [Line Items]    
Total non-interest-bearing accounts $ 522,407 $ 415,575