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INVESTMENT SECURITIES - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Trading gain (losses) recorded in servicing income	$ (0.9)	$ (2.6)	$ (1.4)	$ (6.4)
Tax exempt interest income on available-for-sale securities	$ 2.8	$ 3.1	$ 8.4	$ 8.9
Mortgage Backed Securities and Collateralized Mortgage Obligations
Debt Securities, Available-for-sale [Line Items]
Weighted average yield	3.09%		3.09%		3.08%
US Treasury Notes Securities | Not Designated as Hedging Instrument, Economic Hedge
Debt Securities, Available-for-sale [Line Items]
Trading securities	$ 22.0		$ 22.0		$ 19.0

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Available for sale securities debt maturities without single maturity date weighted average yield.

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Amount of unrealized and realized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in net income (trading).

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