ALLOWANCE FOR CREDIT LOSSES ON LOANS AND LEASES - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Dec. 31, 2024	Dec. 31, 2023
Financing Receivable, Allowance for Credit Loss [Line Items]
Percentage of increase, housing price index	7.00%		7.40%
Percentage of increase, commercial real estate price index	4.90%		3.90%
Percentage of increase (decline), S&P volatility in next fiscal year	25.10%		34.90%
Percentage of increase (decline), S&P volatility in next second year	0.00%		2.50%
Allowance for credit loss	$ 429.0		$ 423.0
Financing receivable, provision for credit losses	17.0	$ 14.0
Allowance for credit losses on loans and leases
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for credit loss	428.9	406.3	$ 422.8	$ 405.6
Financing receivable, allowance for credit loss, period increase	$ 6.1
Financing receivable, allowance for credit loss, period increase, percentage	1.40%
Financing receivable, allowance for credit loss, ratio	1.25%		1.25%
Financing receivable, provision for credit losses	$ 18.6	13.5
Financing receivable, allowance for credit loss, net charge-offs (recovery)	$ 12.5	$ 12.8
Financing receivable, allowance for credit loss, net charge-offs (recovery), percentage	0.15%	0.16%
Allowance for credit losses on loans and leases and allowance for unfunded loan commitments
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for credit loss	$ 449.2	$ 428.2	$ 444.2	$ 427.1
Financing receivable, provision for credit losses	17.5	13.9
Financing receivable, allowance for credit loss, net charge-offs (recovery)	$ 12.5	$ 12.8