BORROWINGS - Additional Information (Details) $ in Millions	3 Months Ended
	Mar. 31, 2024 USD ($) trust	Dec. 31, 2023 USD ($)
Debt Instrument [Line Items]
Short-term advances	$ 300.0	$ 400.0
Short-term advances, overnight maturities, percentage	20.80%	21.10%
Number of unconsolidated subsidiary trusts | trust	4
SOFR
Debt Instrument [Line Items]
Federal home loan bank, advances, interest rate	0.326%
Trust Preferred Securities | SOFR
Debt Instrument [Line Items]
Tenor spread adjustment	0.0026
FHLB
Debt Instrument [Line Items]
Credit available with FHLB	$ 11,400.0
Credit with FHLB utilized	2,800.0
FHLB | Letter of Credit
Debt Instrument [Line Items]
Credit with FHLB utilized	650.0
Other Wholesale Credit
Debt Instrument [Line Items]
Remaining borrowing capacity	$ 8,100.0
Maximum | FHLB
Debt Instrument [Line Items]
Effective interest rates	4.88%	4.88%
Minimum | FHLB
Debt Instrument [Line Items]
Effective interest rates	4.23%	4.23%
FHLB
Debt Instrument [Line Items]
Short-term advances	$ 540.0	$ 450.0
Short-term advances, overnight maturities, percentage	37.50%	23.70%
Other Subordinated Debt | Maximum
Debt Instrument [Line Items]
Debt term	1 year