Investments- Carrying Amounts Of Equity Method Limited Partnership Interest (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Net Investment Income [Line Items]
Limited partnership interests	$ 983.7	$ 712.8
Commercial mortgage loan funds
Net Investment Income [Line Items]
Limited partnership interests	593.6	346.8
Private equity funds
Net Investment Income [Line Items]
Limited partnership interests	76.3	74.0
Infrastructure equity funds
Net Investment Income [Line Items]
Limited partnership interests	72.0	58.3
Real estate equity funds
Net Investment Income [Line Items]
Limited partnership interests	71.3	46.3
Infrastructure debt funds
Net Investment Income [Line Items]
Limited partnership interests	60.0	62.4
Other funds
Net Investment Income [Line Items]
Limited partnership interests	$ 110.5	$ 125.0