ALLOWANCE FOR CREDIT LOSSES ON LOANS AND LEASES - Schedule of Changes in Allowance for Credit Losses (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Allowance for Loan and Lease Losses [Roll Forward]
Balance at Beginning of Year	$ 423.0
Charge- Offs	(84.7)	$ (81.8)
Provision for Credit Losses	86.0	79.8	$ 72.0
Balance at End of Year	439.0	423.0
Unfunded loan commitment
Allowance for Loan and Lease Losses [Roll Forward]
Balance at Beginning of Year	21.4	21.5	21.4
Charge- Offs	0.0	0.0	0.0
Recoveries	0.0	0.0	0.0
Net Charge- Offs	0.0	0.0	0.0
Provision for Credit Losses	(1.3)	(0.1)	0.1
Balance at End of Year	20.1	21.4	21.5
Total commercial loans and leases
Allowance for Loan and Lease Losses [Roll Forward]
Balance at Beginning of Year	279.7	279.3	281.7
Charge- Offs	(72.8)	(64.0)	(68.1)
Recoveries	10.4	13.3	9.2
Net Charge- Offs	(62.4)	(50.7)	(58.9)
Provision for Credit Losses	88.1	51.1	56.5
Balance at End of Year	305.4	279.7	279.3
Total commercial loans and leases | Commercial real estate
Allowance for Loan and Lease Losses [Roll Forward]
Balance at Beginning of Year	166.9	166.6	162.1
Charge- Offs	(30.0)	(38.6)	(12.4)
Recoveries	1.3	2.5	4.4
Net Charge- Offs	(28.7)	(36.1)	(8.0)
Provision for Credit Losses	37.7	36.4	12.5
Balance at End of Year	175.9	166.9	166.6
Total commercial loans and leases | Commercial and industrial
Allowance for Loan and Lease Losses [Roll Forward]
Balance at Beginning of Year	85.6	87.8	102.1
Charge- Offs	(37.9)	(20.9)	(51.2)
Recoveries	8.1	9.3	3.8
Net Charge- Offs	(29.8)	(11.6)	(47.4)
Provision for Credit Losses	43.1	9.4	33.1
Balance at End of Year	98.9	85.6	87.8
Total commercial loans and leases | Commercial leases
Allowance for Loan and Lease Losses [Roll Forward]
Balance at Beginning of Year	22.9	21.2	13.5
Charge- Offs	(0.2)	(0.3)	0.0
Recoveries	0.0	0.1	0.0
Net Charge- Offs	(0.2)	(0.2)	0.0
Provision for Credit Losses	3.5	1.9	7.7
Balance at End of Year	26.2	22.9	21.2
Total commercial loans and leases | Other
Allowance for Loan and Lease Losses [Roll Forward]
Balance at Beginning of Year	4.3	3.7	4.0
Charge- Offs	(4.7)	(4.2)	(4.5)
Recoveries	1.0	1.4	1.0
Net Charge- Offs	(3.7)	(2.8)	(3.5)
Provision for Credit Losses	3.8	3.4	3.2
Balance at End of Year	4.4	4.3	3.7
Total commercial loans and leases | Unfunded loan commitment
Allowance for Loan and Lease Losses [Roll Forward]
Provision for Credit Losses	(1.1)	0.1	0.3
Total consumer loans
Allowance for Loan and Lease Losses [Roll Forward]
Balance at Beginning of Year	143.1	126.3	120.0
Charge- Offs	(11.9)	(17.8)	(13.0)
Recoveries	3.8	5.8	4.2
Net Charge- Offs	(8.1)	(12.0)	(8.8)
Provision for Credit Losses	(0.9)	28.8	15.1
Balance at End of Year	134.1	143.1	126.3
Total consumer loans | Direct installment
Allowance for Loan and Lease Losses [Roll Forward]
Balance at Beginning of Year	29.1	33.8	35.9
Charge- Offs	(0.9)	(1.8)	(0.6)
Recoveries	0.7	1.1	0.6
Net Charge- Offs	(0.2)	(0.7)	0.0
Provision for Credit Losses	(3.2)	(4.0)	(2.1)
Balance at End of Year	25.7	29.1	33.8
Total consumer loans | Residential mortgages
Allowance for Loan and Lease Losses [Roll Forward]
Balance at Beginning of Year	95.9	70.5	55.5
Charge- Offs	(2.4)	(2.6)	(0.7)
Recoveries	0.5	1.2	0.5
Net Charge- Offs	(1.9)	(1.4)	(0.2)
Provision for Credit Losses	(1.6)	26.8	15.2
Balance at End of Year	92.4	95.9	70.5
Total consumer loans | Indirect installment
Allowance for Loan and Lease Losses [Roll Forward]
Balance at Beginning of Year	9.5	12.8	17.3
Charge- Offs	(7.6)	(11.8)	(10.7)
Recoveries	2.2	2.6	2.3
Net Charge- Offs	(5.4)	(9.2)	(8.4)
Provision for Credit Losses	4.9	5.9	3.9
Balance at End of Year	9.0	9.5	12.8
Total consumer loans | Consumer lines of credit
Allowance for Loan and Lease Losses [Roll Forward]
Balance at Beginning of Year	8.6	9.2	11.3
Charge- Offs	(1.0)	(1.6)	(1.0)
Recoveries	0.4	0.9	0.8
Net Charge- Offs	(0.6)	(0.7)	(0.2)
Provision for Credit Losses	(1.0)	0.1	(1.9)
Balance at End of Year	7.0	8.6	9.2
Total consumer loans | Unfunded loan commitment
Allowance for Loan and Lease Losses [Roll Forward]
Provision for Credit Losses	(0.2)	(0.2)	(0.2)
Allowance for credit losses on loans and leases
Allowance for Loan and Lease Losses [Roll Forward]
Balance at Beginning of Year	422.8	405.6	401.7
Charge- Offs	(84.7)	(81.8)	(81.1)
Recoveries	14.2	19.1	13.4
Net Charge- Offs	(70.5)	(62.7)	(67.7)
Provision for Credit Losses	87.2	79.9	71.6
Balance at End of Year	439.5	422.8	405.6
Allowance for credit losses on loans and leases and allowance for unfunded loan commitments
Allowance for Loan and Lease Losses [Roll Forward]
Balance at Beginning of Year	444.2	427.1	423.1
Charge- Offs	(84.7)	(81.8)	(81.1)
Recoveries	14.2	19.1	13.4
Net Charge- Offs	(70.5)	(62.7)	(67.7)
Provision for Credit Losses	85.9	79.8	71.7
Balance at End of Year	$ 459.6	$ 444.2	$ 427.1