Financial Instruments with Off-Balance Sheet Risk (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021	Dec. 31, 2020
Entity Information [Line Items]
Off-Balance Sheet, Credit Loss, Liability	$ 6.2	$ 3.4	$ 6.2	$ 3.4	$ 6.2	$ 3.8	$ 3.4	$ 3.7
Provision for (reversal of) credit loss expense	1.7	0.0	(55.6)	4.8
Credit Extension Commitments	4,840.8		4,840.8			2,539.8
Unused Credit Card Lines
Entity Information [Line Items]
Credit Extension Commitments	811.9		811.9			681.6
Standby Letter of Credit
Entity Information [Line Items]
Credit Extension Commitments	91.6		91.6			$ 57.5
Cumulative effect, period of adoption, adjusted balance
Entity Information [Line Items]
Provision for (reversal of) credit loss expense	$ 0.0	$ 0.0	$ 2.4	$ (0.3)