Investment Securities - Credit Quality Indicators (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	$ 2,688.4	$ 3,208.7
US Treasury Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	99.8	399.0
State, county and municipal securities
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	176.3	179.2
US Government Agencies Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	470.1	354.5
Corporate Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	57.0	57.0
Commercial Mortgage Backed Securities
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	374.9	510.5
Residential Mortgage-Backed Securities
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	1,082.5	1,232.6
Collateralized Mortgage Obligations
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	$ 427.8	$ 475.9