Derivative Financial Instruments Fair Value Hedges Carrying Amount of Hedged Assets and Cumulative Basis Adjustments (Details) - Interest Rate Swaps - Receive Fixed/Pay Fixed - Designated as Hedging Instrument - Fair Value Hedging - Fixed Maturity Securities - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Derivative Instruments and Hedging Activities Disclosures
Hedged Asset, Fair Value Hedge	$ 466.8	$ 466.3
Hedged Asset, Fair Value Hedge, Cumulative Increase (Decrease)	$ (3.3)	$ 2.0