OTHER BORROWINGS - Narrative (Details) - USD ($) $ in Millions	Oct. 01, 2025	Jun. 01, 2025	Dec. 15, 2024	Mar. 15, 2022	Jul. 01, 2019	Dec. 31, 2024	Dec. 31, 2023	Sep. 28, 2020	Dec. 06, 2019
Debt Instrument [Line Items]
Federal home loan bank, advances, general debt obligations, amount of available, unused funds						$ 3,680.0
Credit arrangements for federal funds purchase						92.0
Pledged assets separately reported, loans pledged for federal reserve bank, at fair value						2,890.0
Loans pledged at federal reserve discount window available for borrowing						2,280.0
Senior Subordinated Notes
Debt Instrument [Line Items]
Redemption price (as a percent)				100.00%
Subordinated notes payable due December 15, 2029 net of unamortized debt issuance cost of $0 and $1,296, respectively; fixed interest rate of 4.25% through December 14, 2024; variable interest rate thereafter at three-month SOFR plus 2.94% (2029 subordinated notes) | Senior Subordinated Notes
Debt Instrument [Line Items]
Face amount						2.3	$ 12.0	$ 110.0	$ 120.0
Interest rate, stated (as a percent)								3.875%	4.25%
Basis spread on variable rate (as a percent)			2.94%
Redemption price (as a percent)			100.00%
Subordinated notes payable due December 15, 2029 net of unamortized debt issuance cost of $0 and $1,296, respectively; fixed interest rate of 4.25% through December 14, 2024; variable interest rate thereafter at three-month SOFR plus 2.94% (2029 subordinated notes) | Scenario, Forecast | Senior Subordinated Notes
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	3.753%
Redemption price (as a percent)	100.00%
Subordinated notes payable due May 31, 2030 net of unaccreted purchase accounting fair value adjustment of $653 and $784, respectively; fixed interest rate of 5.875% through May 31, 2025; variable interest rate thereafter at three-month SOFR plus 3.63% (Bank subordinated notes) (1) | Senior Subordinated Notes
Debt Instrument [Line Items]
Face amount					$ 75.0	$ 1.0
Interest rate, stated (as a percent)					5.875%
Unaccreted purchase accounting fair value adjustment					$ 1.3
Subordinated notes payable due May 31, 2030 net of unaccreted purchase accounting fair value adjustment of $653 and $784, respectively; fixed interest rate of 5.875% through May 31, 2025; variable interest rate thereafter at three-month SOFR plus 3.63% (Bank subordinated notes) (1) | Scenario, Forecast | Senior Subordinated Notes
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)		3.63%
Redemption price (as a percent)		100.00%