Quarterly report [Sections 13 or 15(d)]

INVESTMENT SECURITIES - Schedule of trading and available-for-sale securities (Details)

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INVESTMENT SECURITIES - Schedule of trading and available-for-sale securities (Details) - USD ($)
$ in Thousands
Dec. 31, 2025
Mar. 31, 2025
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Total trading securities $ 2,183,567 $ 2,275,286
Total available-for-sale securities, at fair value 521,543 473,587
Total held-to-maturity securities 424,329 65,860
Total investment securities 3,129,439 2,814,733
Non-U.S. sovereign debt    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Total trading securities 1,258,870 1,282,450
Total available-for-sale securities, at fair value 169,088 208,231
Non-U.S. sovereign debt 424,562 65,914
Allowance for Non-US sovereign debt (233) (54)
Total held-to-maturity securities 424,329 65,860
Corporate debt    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Total trading securities 727,939 807,985
Total available-for-sale securities, at fair value 330,400 243,730
Corporate equity    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Total trading securities 157,481 106,227
U.S. sovereign debt    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Total trading securities 33,184 73,787
Total available-for-sale securities, at fair value 22,055 21,626
Exchange traded notes and funds    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Total trading securities $ 6,093 $ 4,837