Investment Securities - Credit Quality Indicators (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	$ 2,342.6	$ 2,688.4
US Treasury Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity		99.8
State, county and municipal securities
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	173.2	176.3
US Government Agencies Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	462.3	470.1
Corporate Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	29.9	57.0
Commercial Mortgage Backed Securities
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	354.8	374.9
Residential Mortgage-Backed Securities
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	941.3	1,082.5
Collateralized Mortgage Obligations
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	$ 381.1	$ 427.8