Securities (Investment Security Gains and Losses by Security Type) (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Schedule of Held-to-maturity Securities [Line Items]
Investment Security Gains (Losses), net	$ 0	$ 0	$ 0	$ (189,300,000)
U.S. Government
Schedule of Held-to-maturity Securities [Line Items]
Investment Security Gains (Losses), net	0	0	0	(34,800,000)
Obligations of States and Political Subdivisions
Schedule of Held-to-maturity Securities [Line Items]
Investment Security Gains (Losses), net	0	0	0	0
Government Sponsored Agency
Schedule of Held-to-maturity Securities [Line Items]
Investment Security Gains (Losses), net	0	0	0	(23,000,000.0)
Corporate Debt
Schedule of Held-to-maturity Securities [Line Items]
Investment Security Gains (Losses), net	0	0	0	0
Covered Bonds
Schedule of Held-to-maturity Securities [Line Items]
Investment Security Gains (Losses), net	0	0	0	(4,200,000)
Sub-Sovereign, Supranational and Non-U.S. Agency Bonds
Schedule of Held-to-maturity Securities [Line Items]
Investment Security Gains (Losses), net	0	0	0	(48,200,000)
Other Asset-Backed
Schedule of Held-to-maturity Securities [Line Items]
Investment Security Gains (Losses), net	0	0	0	(56,500,000)
Commercial Mortgage-Backed
Schedule of Held-to-maturity Securities [Line Items]
Investment Security Gains (Losses), net	$ 0	$ 0	$ 0	$ (22,600,000)