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Equity Method Investments in Affiliates - Additional Information (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2021 | Jun. 30, 2020 | Mar. 31, 2020 | Jun. 30, 2021 | Jun. 30, 2020
Acquired Client Relationships |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Amortization of Intangible Assets |  |  |  | $ 16.4 |
Estimated Future Amortization Expense of Finite-Lived Intangibles |  |  |  |  |
Finite-lived intangible, future amortization expense, remainder of fiscal year | $ 15.0 |  |  | 15.0 |
Finite-lived intangible, future amortization expense in year one | 30.0 |  |  | 30.0 |
Finite-lived intangible, future amortization expense in year two | 30.0 |  |  | 30.0 |
Finite-lived intangible, future amortization expense in year three | 15.0 |  |  | 15.0 |
Finite-lived intangible, future amortization expense in year four | 10.0 |  |  | 10.0 |
Finite-lived intangible, future amortization expense in year five | 10.0 |  |  | 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 |  |  | 104.4 |
Contingent payments in 2021 | 26.9 |  |  | 26.9 |
Contingent payments in year one | 77.5 |  |  | 77.5 |
Equity Method Investee | Acquired Client Relationships |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Amortization of Intangible Assets | 29.3 | $ 36.9 |  | 64.5 | $ 76.2
Estimated Future Amortization Expense of Finite-Lived Intangibles |  |  |  |  |
Finite-lived intangible, future amortization expense, remainder of fiscal year | 60.0 |  |  | 60.0 |
Finite-lived intangible, future amortization expense in year one | 80.0 |  |  | 80.0 |
Finite-lived intangible, future amortization expense in year two | 80.0 |  |  | 80.0 |
Finite-lived intangible, future amortization expense in year three | 50.0 |  |  | 50.0 |
Finite-lived intangible, future amortization expense in year four | 50.0 |  |  | 50.0 |
Finite-lived intangible, future amortization expense in year five | $ 50.0 |  |  | $ 50.0 |

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