Allowance for Credit Losses (Changes in Allowance for Credit Losses Related to Loan and Leases) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
LOANS AND LEASES
Balance at beginning of period	$ 190.7	$ 104.5	$ 112.6
Charge-Offs	(0.7)	(9.7)	(6.5)
Recoveries	7.0	6.5	7.2
Net Recoveries (Charge-Offs)	6.3	(3.2)	0.7
Provision for Credit Losses	(58.6)	91.6	(8.8)
Balance at end of period	138.4	190.7	104.5
UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT
Balance at Beginning of Period	61.1	19.9	25.6
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	(27.0)	32.3	(5.7)
Balance at End of Period	34.1	61.1	19.9
COMMERCIAL
LOANS AND LEASES
Balance at beginning of period	142.2	58.1	57.6
Charge-Offs	(0.3)	(6.3)	(3.0)
Recoveries	0.9	2.4	0.9
Net Recoveries (Charge-Offs)	0.6	(3.9)	(2.1)
Provision for Credit Losses	(37.2)	93.9	2.6
Balance at end of period	105.6	142.2	58.1
UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT
Balance at Beginning of Period	57.6	15.8	21.1
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	(26.2)	29.9	(5.3)
Balance at End of Period	31.4	57.6	15.8
PERSONAL
LOANS AND LEASES
Balance at beginning of period	48.5	46.4	55.0
Charge-Offs	(0.4)	(3.4)	(3.5)
Recoveries	6.1	4.1	6.3
Net Recoveries (Charge-Offs)	5.7	0.7	2.8
Provision for Credit Losses	(21.4)	(2.3)	(11.4)
Balance at end of period	32.8	48.5	46.4
UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT
Balance at Beginning of Period	3.5	4.1	4.5
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	(0.8)	2.4	(0.4)
Balance at End of Period	$ 2.7	3.5	4.1
Cumulative Effect Adjustment
LOANS AND LEASES
Balance at beginning of period		(2.2)
Balance at end of period			(2.2)
UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT
Balance at Beginning of Period		8.9
Balance at End of Period			8.9
Cumulative Effect Adjustment | COMMERCIAL
LOANS AND LEASES
Balance at beginning of period		(5.9)
Balance at end of period			(5.9)
UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT
Balance at Beginning of Period		11.9
Balance at End of Period			11.9
Cumulative Effect Adjustment | PERSONAL
LOANS AND LEASES
Balance at beginning of period		3.7
Balance at end of period			3.7
UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT
Balance at Beginning of Period		(3.0)
Balance at End of Period			(3.0)
Adjusted Balance
LOANS AND LEASES
Balance at beginning of period		102.3
Balance at end of period			102.3
UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT
Balance at Beginning of Period		28.8
Balance at End of Period			28.8
Adjusted Balance | COMMERCIAL
LOANS AND LEASES
Balance at beginning of period		52.2
Balance at end of period			52.2
UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT
Balance at Beginning of Period		27.7
Balance at End of Period			27.7
Adjusted Balance | PERSONAL
LOANS AND LEASES
Balance at beginning of period		50.1
Balance at end of period			50.1
UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT
Balance at Beginning of Period		$ 1.1
Balance at End of Period			$ 1.1