Derivative Financial Instruments Fair Value Hedges Carrying Amount of Hedged Assets and Liabilities and Cumulative Basis Adjustments (Details) - Receive Fixed/Pay Fixed - Designated as Hedging Instrument - Fair Value Hedging - USD ($) $ in Millions	Jun. 30, 2026	Dec. 31, 2025
Derivative Instruments and Hedging Activities Disclosures
Hedged Asset, Fair Value Hedge, Cumulative Increase	$ 9.2	$ 24.7
Hedged Asset, Fair Value Hedge	790.2	695.0
hedged asset, amortized cost	$ 891.6	$ 793.4
Hedged Asset, Statement of Financial Position [Extensible Enumeration]	Debt Securities, Available-for-Sale	Debt Securities, Available-for-Sale