Allowance for Credit Losses (Changes in Allowance for Credit Losses Related to Loan and Leases) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
LOANS AND LEASES
Balance at Beginning of Period	$ 138.4	$ 190.7	$ 104.5
Charge-Offs	6.0	0.7	9.7
Recoveries	10.2	7.0	6.5
Net Recoveries (Charge-Offs)	4.2	6.3	(3.2)
Provision for Credit Losses	1.7	(58.6)	91.6
Balance at End of Period	144.3	138.4	190.7
UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT
Balance at Beginning of Period	34.1	61.1	19.9
Charge-Offs	0.0	0.0	0.0
Recoveries	0.0	0.0	0.0
Net Recoveries (Charge-Offs)	0.0	0.0	0.0
Provision for Credit Losses	4.4	(27.0)	32.3
Balance at End of Period	38.5	34.1	61.1
Adjustment
LOANS AND LEASES
Balance at Beginning of Period			(2.2)
UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT
Balance at Beginning of Period			8.9
Adjusted Balance
LOANS AND LEASES
Balance at Beginning of Period			102.3
UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT
Balance at Beginning of Period			28.8
Commercial
LOANS AND LEASES
Balance at Beginning of Period	105.6	142.2	58.1
Charge-Offs	5.3	0.3	6.3
Recoveries	2.7	0.9	2.4
Net Recoveries (Charge-Offs)	(2.6)	0.6	(3.9)
Provision for Credit Losses	13.2	(37.2)	93.9
Balance at End of Period	116.2	105.6	142.2
UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT
Balance at Beginning of Period	31.4	57.6	15.8
Charge-Offs	0.0	0.0	0.0
Recoveries	0.0	0.0	0.0
Net Recoveries (Charge-Offs)	0.0	0.0	0.0
Provision for Credit Losses	4.9	(26.2)	29.9
Balance at End of Period	36.3	31.4	57.6
Commercial | Adjustment
LOANS AND LEASES
Balance at Beginning of Period			(5.9)
UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT
Balance at Beginning of Period			11.9
Commercial | Adjusted Balance
LOANS AND LEASES
Balance at Beginning of Period			52.2
UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT
Balance at Beginning of Period			27.7
PERSONAL
LOANS AND LEASES
Balance at Beginning of Period	32.8	48.5	46.4
Charge-Offs	0.7	0.4	3.4
Recoveries	7.5	6.1	4.1
Net Recoveries (Charge-Offs)	6.8	5.7	0.7
Provision for Credit Losses	(11.5)	(21.4)	(2.3)
Balance at End of Period	28.1	32.8	48.5
UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT
Balance at Beginning of Period	2.7	3.5	4.1
Charge-Offs	0.0	0.0	0.0
Recoveries	0.0	0.0	0.0
Net Recoveries (Charge-Offs)	0.0	0.0	0.0
Provision for Credit Losses	(0.5)	(0.8)	2.4
Balance at End of Period	$ 2.2	$ 2.7	3.5
PERSONAL | Adjustment
LOANS AND LEASES
Balance at Beginning of Period			3.7
UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT
Balance at Beginning of Period			(3.0)
PERSONAL | Adjusted Balance
LOANS AND LEASES
Balance at Beginning of Period			50.1
UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT
Balance at Beginning of Period			$ 1.1