Investments - Carrying Amount of Equity Method Limited Partnership Interests (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Schedule of Equity Method Investments
Limited partnership interests	$ 1,073.8	$ 983.7
Commercial mortgage loan funds
Schedule of Equity Method Investments
Limited partnership interests	642.7	593.6
Private equity funds
Schedule of Equity Method Investments
Limited partnership interests	80.6	76.3
Infrastructure equity funds
Schedule of Equity Method Investments
Limited partnership interests	62.8	60.0
Real estate equity funds
Schedule of Equity Method Investments
Limited partnership interests	86.8	71.3
Infrastructure debt funds
Schedule of Equity Method Investments
Limited partnership interests	72.4	72.0
Other funds
Schedule of Equity Method Investments
Limited partnership interests	$ 128.5	$ 110.5