Investments - Carrying Amount of Equity Method Limited Partnership Interests (Details) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Schedule of Equity Method Investments
Limited partnership interests	$ 997.5	$ 712.8
Commercial mortgage loan funds
Schedule of Equity Method Investments
Limited partnership interests	601.5	346.8
Private equity funds
Schedule of Equity Method Investments
Limited partnership interests	73.4	74.0
Infrastructure equity funds
Schedule of Equity Method Investments
Limited partnership interests	70.2	58.3
Infrastructure debt funds
Schedule of Equity Method Investments
Limited partnership interests	67.4	62.4
Other funds
Schedule of Equity Method Investments
Limited partnership interests	$ 185.0	$ 171.3