Derivative Financial Instruments Nature and Amount of Collateral Received From and Posted To Our Derivative Counterparties (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Derivative
Derivative Asset, Subject to Master Netting Arrangement, Deduction of Financial Instrument Not Offset	$ 20.5	$ 37.4
Derivative Liability, Subject to Master Netting Arrangement, Deduction of Financial Instrument Not Offset	82.2	39.8
Cash
Derivative
Cash Collateral from Counterparties	3.2	11.1
Derivative, Collateral, Right to Reclaim Cash	0.0	0.0
Fixed Maturity Securities
Derivative
Carrying Value of Fixed Maturity Securities Posted as Collateral to Counterparties	17.3	26.3
Carrying Value of Fixed Maturity Securities Posted as Collateral to Counterparties	$ 82.2	$ 39.8