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Equity Method Investments in Affiliates - Additional Information (Details) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2021 USD ($) affiliate | Dec. 31, 2020 USD ($) affiliate | Mar. 31, 2020 USD ($) | Dec. 31, 2021 USD ($) affiliate | Dec. 31, 2020 USD ($) affiliate | Dec. 31, 2019 USD ($)
Estimated Future Amortization Expense of Finite-Lived Intangibles |  |  |  |  |  |
Contingent payment obligation | $ 709.2 | $ 452.2 |  | $ 709.2 | $ 452.2 |
Number of affiliates accounted for under the equity method | affiliate | 21 | 18 |  | 21 | 18 |
Acquired Client Relationships |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Intangible amortization expense |  |  |  | $ 35.7 | $ 69.8 |
Estimated Future Amortization Expense of Finite-Lived Intangibles |  |  |  |  |  |
Intangible future amortization expense in 2022 | $ 50.0 |  |  | 50.0 |  |
Intangible future amortization expense in 2023 | 50.0 |  |  | 50.0 |  |
Intangible future amortization expense in 2024 | 35.0 |  |  | 35.0 |  |
Intangible future amortization expense in 2025 | 30.0 |  |  | 30.0 |  |
Intangible future amortization expense in 2026 | 30.0 |  |  | 30.0 |  |
Equity Method Investee |  |  |  |  |  |
Estimated Future Amortization Expense of Finite-Lived Intangibles |  |  |  |  |  |
Impairment expense | 52.0 | $ 45.0 | $ 140.0 |  |  |
Deferred payment obligations payable in 2022 | 50.8 |  |  | 50.8 |  |
Equity Method Investee | Achievement of Specified Financial Targets |  |  |  |  |  |
Estimated Future Amortization Expense of Finite-Lived Intangibles |  |  |  |  |  |
Contingent payment obligation | $ 43.0 |  |  | $ 43.0 |  |
Equity Method Investee | Growth rate period |  |  |  |  |  |
Estimated Future Amortization Expense of Finite-Lived Intangibles |  |  |  |  |  |
Measurement input | 5 | 5 | 5 | 5 | 5 |
Equity Method Investee | Growth rate |  |  |  |  |  |
Estimated Future Amortization Expense of Finite-Lived Intangibles |  |  |  |  |  |
Measurement input | 0.003 | (0.05) | (0.02) | 0.003 | (0.05) |
Equity Method Investee | Market participant tax rates |  |  |  |  |  |
Estimated Future Amortization Expense of Finite-Lived Intangibles |  |  |  |  |  |
Measurement input | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 |
Equity Method Investee | Discount rates, asset based fees |  |  |  |  |  |
Estimated Future Amortization Expense of Finite-Lived Intangibles |  |  |  |  |  |
Measurement input | 0.11 | 0.11 | 0.11 | 0.11 | 0.11 |
Equity Method Investee | Discount rates, performance based fees |  |  |  |  |  |
Estimated Future Amortization Expense of Finite-Lived Intangibles |  |  |  |  |  |
Measurement input | 0.20 | 0.20 | 0.20 | 0.20 | 0.20 |
Equity Method Investee | Acquired Client Relationships |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Intangible amortization expense |  |  |  | $ 123.0 | $ 147.0 | $ 142.4
Estimated Future Amortization Expense of Finite-Lived Intangibles |  |  |  |  |  |
Intangible future amortization expense in 2022 | $ 80.0 |  |  | 80.0 |  |
Intangible future amortization expense in 2023 | 80.0 |  |  | 80.0 |  |
Intangible future amortization expense in 2024 | 50.0 |  |  | 50.0 |  |
Intangible future amortization expense in 2025 | 50.0 |  |  | 50.0 |  |
Intangible future amortization expense in 2026 | $ 50.0 |  |  | $ 50.0 |  |

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