INVESTMENT SECURITIES - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]
Trading gains (losses) recorded in servicing income	$ 1.1	$ (0.9)	$ 0.2	$ (1.4)
Tax exempt interest income on available-for-sale securities	$ 2.8	$ 2.8	$ 8.4	$ 8.4
Mortgage Backed Securities and Collateralized Mortgage Obligations
Debt Securities, Available-for-sale [Line Items]
Weighted average yield	3.12%		3.12%		3.21%
US Treasury Notes Securities | Not Designated as Hedging Instrument, Economic Hedge
Debt Securities, Available-for-sale [Line Items]
Trading securities	$ 38.0		$ 38.0		$ 25.0