NOTE 4 - SECURITIZATIONS AND VARIABLE INTEREST ENTITIES - Securitization (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2025 USD ($) item	Mar. 31, 2026 USD ($)	Aug. 31, 2025 USD ($)	Mar. 31, 2025 USD ($)
SECURITIZATIONS AND VARIABLE INTEREST ENTITIES
Pledged securities held to maturity, at amortized cost	$ 948,676	$ 951,916
Liabilities	8,385,883	8,491,231
Assets	$ 9,498,194	9,613,695		$ 9,082,188
Number of sponsored securitizations completed | item	4
VIE - Not Primary
SECURITIZATIONS AND VARIABLE INTEREST ENTITIES
Liabilities	$ 0	0
Assets	83,900	82,700
Maximum exposure to loss		85,500
Assets pledged as collateral
SECURITIZATIONS AND VARIABLE INTEREST ENTITIES
Pledged securities held to maturity, at amortized cost	$ 176,632	$ 175,841	$ 200,300
Assets pledged as collateral | Class A municipal certificates
SECURITIZATIONS AND VARIABLE INTEREST ENTITIES
Pledged securities held to maturity, at amortized cost			134,200
Assets pledged as collateral | Class B municipal certificates
SECURITIZATIONS AND VARIABLE INTEREST ENTITIES
Pledged securities held to maturity, at amortized cost			$ 66,100