INVESTMENT SECURITIES AND OTHER SECURITIES - Narrative (Details) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2025 USD ($)	Dec. 31, 2025 USD ($) security	Dec. 31, 2024 USD ($)
Debt Securities, Available-for-Sale [Line Items]
Number of municipal bonds classified as AFS debt securities | security		1
AFS debt security charge-off		$ 2
Recovery of previously written-off available-for-sale municipal security	$ 3
Allowance related to investment securities, available for sale securities		0	$ 0
Allowance related to investment securities		0	0
Asset Pledged as Collateral
Debt Securities, Available-for-Sale [Line Items]
Investment securities		$ 29,700	$ 37,700