Equity Method Investments in Affiliates - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Acquired Client Relationships
Schedule of Equity Method Investments [Line Items]
Amortization of Intangible Assets	$ 7.5
Estimated Future Amortization Expense of Finite-Lived Intangibles
Finite-lived intangible, future amortization expense in 2021	23.0
Finite-lived intangible, future amortization expense in 2022	30.0
Finite-lived intangible, future amortization expense in 2023	30.0
Finite-lived intangible, future amortization expense in 2024	20.0
Finite-lived intangible, future amortization expense in 2025	20.0
Finite-lived intangible, future amortization expense in 2026	10.0
Equity Method Investee
Estimated Future Amortization Expense of Finite-Lived Intangibles
Impairment expense		$ 140.0
Average projected growth rate period		5 years
Average projected growth rate		(2.00%)
Discount rate for assets based fees		11.00%
Discount rate for performance fees		20.00%
Market participant tax rate		25.00%
Total contingent payments	104.4
Contingent payments in 2021	26.9
Contingent payments in 2022	77.5
Equity Method Investee \| Acquired Client Relationships
Schedule of Equity Method Investments [Line Items]
Amortization of Intangible Assets	35.2	$ 39.3
Estimated Future Amortization Expense of Finite-Lived Intangibles
Finite-lived intangible, future amortization expense in 2021	85.0
Finite-lived intangible, future amortization expense in 2022	50.0
Finite-lived intangible, future amortization expense in 2023	50.0
Finite-lived intangible, future amortization expense in 2024	50.0
Finite-lived intangible, future amortization expense in 2025	50.0
Finite-lived intangible, future amortization expense in 2026	$ 40.0

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