Securities (Investment Security Gains and Losses by Security Type) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Schedule of Held-to-maturity Securities [Line Items]
Investment Security Gains (Losses), net	$ (214.0)	$ (0.3)	$ (0.4)
Obligations of States and Political Subdivisions
Schedule of Held-to-maturity Securities [Line Items]
Investment Security Gains (Losses), net	(95.8)	0.0	0.0
Government Sponsored Agency
Schedule of Held-to-maturity Securities [Line Items]
Investment Security Gains (Losses), net	0.0	0.0	(1.8)
Corporate Debt
Schedule of Held-to-maturity Securities [Line Items]
Investment Security Gains (Losses), net	(67.3)	(0.3)	(0.4)
Investment Security, Gains (Losses)	1.0
Other Asset-Backed
Schedule of Held-to-maturity Securities [Line Items]
Investment Security Gains (Losses), net	(17.1)	0.0	(0.7)
Commercial Mortgage-Backed
Schedule of Held-to-maturity Securities [Line Items]
Investment Security Gains (Losses), net	$ (33.8)	$ 0.0	$ 2.5