Allowance for Credit Losses (Changes in Allowance for Credit Losses Related to Loan and Leases) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
LOANS AND LEASES
Balance at Beginning of Period	$ 138.4	$ 190.7
Charge-Offs	(0.1)	(0.4)
Recoveries	3.3	1.3
Net Recoveries (Charge-Offs)	3.2	0.9
Provision for Credit Losses	(5.3)	(26.2)
Balance at End of Period	136.3	165.4
UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT
Balance at Beginning of Period	34.1	61.1
Charge-Offs	0.0	0.0
Recoveries	0.0	0.0
Net Recoveries (Charge-Offs)	0.0	0.0
Provision for Credit Losses	3.4	(6.0)
Balance at End of Period	37.5	55.1
COMMERCIAL
LOANS AND LEASES
Balance at Beginning of Period	105.6	142.2
Charge-Offs	0.0	0.0
Recoveries	2.2	0.0
Net Recoveries (Charge-Offs)	2.2	0.0
Provision for Credit Losses	(5.3)	(17.5)
Balance at End of Period	102.5	124.7
UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT
Balance at Beginning of Period	31.4	57.6
Charge-Offs	0.0	0.0
Recoveries	0.0	0.0
Net Recoveries (Charge-Offs)	0.0	0.0
Provision for Credit Losses	3.3	(5.9)
Balance at End of Period	34.7	51.7
PERSONAL
LOANS AND LEASES
Balance at Beginning of Period	32.8	48.5
Charge-Offs	(0.1)	(0.4)
Recoveries	1.1	1.3
Net Recoveries (Charge-Offs)	1.0	0.9
Provision for Credit Losses	0.0	(8.7)
Balance at End of Period	33.8	40.7
UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT
Balance at Beginning of Period	2.7	3.5
Charge-Offs	0.0	0.0
Recoveries	0.0	0.0
Net Recoveries (Charge-Offs)	0.0	0.0
Provision for Credit Losses	0.1	(0.1)
Balance at End of Period	$ 2.8	$ 3.4