Financial Instruments with Off-Balance Sheet Risk (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Jun. 30, 2023	Dec. 31, 2022	Jun. 30, 2022	Dec. 31, 2021
Entity Information [Line Items]
Off-Balance Sheet, Credit Loss, Liability	$ 18.8	$ 9.7	$ 18.8	$ 9.7	$ 20.8	$ 16.2	$ 6.2	$ 3.8
Provision for credit loss expense	(3.2)	(4.6)	(25.3)	(60.2)
Credit Extension Commitments	4,441.0		4,441.0			5,173.3
Unused Credit Card Lines
Entity Information [Line Items]
Credit Extension Commitments	805.1		805.1			827.6
Standby Letter of Credit
Entity Information [Line Items]
Credit Extension Commitments	94.7		94.7			$ 93.8
Cumulative effect, period of adoption, adjusted balance
Entity Information [Line Items]
Provision for credit loss expense	$ (2.0)	$ 3.5	$ 2.6	$ 5.9