Derivative Financial Instruments Fair Value Hedges Carrying Amount of Hedged Assets and Cumulative Basis Adjustments (Details) - Receive Fixed/Pay Fixed - Designated as Hedging Instrument - Fair Value Hedging - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Derivative Instruments and Hedging Activities Disclosures
Hedged Asset, Fair Value Hedge	$ 683.6	$ 695.0
Hedged Asset, Statement of Financial Position [Extensible Enumeration]	Debt Securities, Available-for-Sale	Debt Securities, Available-for-Sale
Derivative Instrument by Balance Sheet Location: us-gaap:AvailableForSaleSecuritiesDebtSecurities
Derivative Instruments and Hedging Activities Disclosures
Hedged Asset, Fair Value Hedge, Cumulative Increase (Decrease)	$ 17.7	$ 24.7
hedged asset, amortized cost	$ 799.8	$ 793.4