v3.26.1
INVESTMENT SECURITIES - Narrative (Details)
$ in Thousands
3 Months Ended 12 Months Ended
Jun. 30, 2026
USD ($)
Mar. 31, 2026
USD ($)
issuer
Defined Benefit Plan Disclosure [Line Items]    
Investment securities $ 4,182,982 $ 3,342,561
Number of issuers | issuer   2
Accumulated impairment loss 495 $ 376
Fair value of held-to-maturity 531,997 449,665
Non-US sovereign debt    
Defined Benefit Plan Disclosure [Line Items]    
Accumulated impairment loss 495 376
Fair value of held-to-maturity 493,722 449,665
Quoted Prices in Active Markets for Identical Assets | Non-US sovereign debt    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of held-to-maturity 323,067 341,132
Significant Other Observable Inputs | Non-US sovereign debt    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of held-to-maturity $ 208,930 $ 108,533
Kazakhstan Sustainability Fund JSC    
Defined Benefit Plan Disclosure [Line Items]    
Percentage of trading securities 10.00% 10.00%
Investment securities $ 550,316 $ 544,306
Ministry of Finance of the Republic of Kazakhstan    
Defined Benefit Plan Disclosure [Line Items]    
Percentage of trading securities 10.00% 10.00%
Investment securities $ 2,733,248 $ 1,897,085