Investments- Carrying Amounts Of Equity Method Limited Partnership Interest (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Net Investment Income
Limited partnership interests	$ 712.8	$ 449.0
Commercial mortgage loan funds
Net Investment Income
Limited partnership interests	346.8	149.6
Private equity funds
Net Investment Income
Limited partnership interests	74.0	39.6
Infrastructure debt funds
Net Investment Income
Limited partnership interests	62.4	58.3
Infrastructure equity funds
Net Investment Income
Limited partnership interests	58.3	52.1
Other funds
Net Investment Income
Limited partnership interests	$ 171.3	$ 149.4