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BORROWINGS - Additional Information (Details) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Oct. 31, 2025 USD ($)	Sep. 30, 2025 USD ($) trust	Jun. 30, 2025 USD ($)	Sep. 30, 2025 USD ($) trust	Dec. 31, 2024 USD ($)
Debt Instrument [Line Items]
Short-term advances		$ 0.0		$ 0.0	$ 0.0
Federal home loan bank, advances, interest rate		0.35%		0.35%	0.34%
Aggregate principal amount		$ 745.0		$ 745.0
Number of unconsolidated subsidiary trusts | trust		4		4
Trust Preferred Securities
Debt Instrument [Line Items]
Basis points, interest rate, type [Extensible Enumeration]				Secured Overnight Financing Rate (SOFR) [Member]
Tenor spread adjustment				0.0026
FHLB
Debt Instrument [Line Items]
Credit available with FHLB		$ 12,600.0		$ 12,600.0
FHLB amount available for borrowing		9,700.0		9,700.0
Collateral pledged		17,600.0		17,600.0
Other Subordinated Debt
Debt Instrument [Line Items]
Debt matured or redeemed			$ 25.0
Aggregate principal amount		245.0		245.0
Other Subordinated Debt | Subsequent Event
Debt Instrument [Line Items]
Debt matured or redeemed	$ 100.0
Other Subordinated Debt | 4.875% Subordinated Notes due 2025
Debt Instrument [Line Items]
Aggregate principal amount		100.0		100.0
Senior Notes
Debt Instrument [Line Items]
Debt matured or redeemed		350.0
Aggregate principal amount		500.0		500.0
Other Wholesale Credit
Debt Instrument [Line Items]
Remaining borrowing capacity		$ 7,100.0		$ 7,100.0
Maximum | FHLB
Debt Instrument [Line Items]
Effective interest rates		4.69%		4.69%	4.88%
Minimum | FHLB
Debt Instrument [Line Items]
Effective interest rates		3.69%		3.69%	3.69%
FHLB
Debt Instrument [Line Items]
Short-term advances		$ 415.0		$ 415.0	$ 335.0
Short-term advances, overnight maturities, percentage		48.00%		48.00%	57.30%
Basis points, interest rate, type [Extensible Enumeration]				Secured Overnight Financing Rate (SOFR) [Member]
Other Subordinated Debt | Maximum
Debt Instrument [Line Items]
Debt term				1 year

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