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INVESTMENT SECURITIES - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]
Trading gains (losses) recorded in servicing income	$ (0.3)	$ (1.1)	$ (0.9)	$ (0.4)
Tax exempt interest income on available-for-sale securities	$ 2.8	$ 2.8	$ 5.6	$ 5.6
Mortgage Backed Securities and Collateralized Mortgage Obligations
Debt Securities, Available-for-sale [Line Items]
Weighted average yield	3.09%		3.09%		3.21%
US Treasury Notes Securities | Not Designated as Hedging Instrument, Economic Hedge
Debt Securities, Available-for-sale [Line Items]
Trading securities	$ 26.0		$ 26.0		$ 25.0

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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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