Investments - Investments in NGP (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Schedule of Equity Method Investments [Line Items]
Total	$ 3,024.1	$ 2,922.0
Investment in NGP Management
Schedule of Equity Method Investments [Line Items]
Total	370.5	369.7
Investments in NGP general partners - accrued performance allocations
Schedule of Equity Method Investments [Line Items]
Total	484.4	564.5
Principal investments in NGP funds
Schedule of Equity Method Investments [Line Items]
Total	61.3	81.5
Total investments in NGP
Schedule of Equity Method Investments [Line Items]
Total	$ 916.2	$ 1,015.7