Equity Method Investments in Affiliates - Schedule of Equity Method Investments in Affiliates (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Schedule of Equity Method Investments [Line Items]
Goodwill	$ 2,659.6	$ 2,648.7
Equity method investments in Affiliates (net)	1,943.8	2,139.5
Equity Method Investee
Schedule of Equity Method Investments [Line Items]
Goodwill	1,280.7	1,262.4
Definite-lived acquired client relationships (net)	441.5	479.4
Indefinite-lived acquired client relationships (net)	121.7	119.0
Undistributed earnings and tangible capital	99.9	278.7
Equity method investments in Affiliates (net)	$ 1,943.8	$ 2,139.5