Annual report [Section 13 and 15(d), not S-K Item 405]

INVESTMENT SECURITIES - Narrative (Details)

v3.26.1
INVESTMENT SECURITIES - Narrative (Details)
$ in Thousands
12 Months Ended
Mar. 31, 2026
USD ($)
issuer
Mar. 31, 2025
USD ($)
issuer
Debt and Equity Securities, FV-NI [Line Items]    
Number of issuers | issuer 2 2
Investment securities $ 3,342,561 $ 2,814,733
Debt securities, available-for-sale, allowance for credit loss 376 406
Fair value of held-to-maturity 449,665 64,952
Non-US sovereign debt    
Debt and Equity Securities, FV-NI [Line Items]    
Debt securities, available-for-sale, allowance for credit loss 376 378
Fair value of held-to-maturity 449,665 64,952
Fair Value, Inputs, Level 1 [Member] | Non-US sovereign debt    
Debt and Equity Securities, FV-NI [Line Items]    
Fair value of held-to-maturity 341,132 45,216
Fair Value, Inputs, Level 2 | Non-US sovereign debt    
Debt and Equity Securities, FV-NI [Line Items]    
Fair value of held-to-maturity $ 108,533 $ 19,736
Kazakhstan Sustainability Fund JSC    
Debt and Equity Securities, FV-NI [Line Items]    
Percentage of trading securities 10.00% 10.00%
Investment securities $ 544,306 $ 578,862
Ministry of Finance of the Republic of Kazakhstan    
Debt and Equity Securities, FV-NI [Line Items]    
Percentage of trading securities 10.00% 10.00%
Investment securities $ 1,897,085 $ 1,527,340