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Equity Method Investments in Affiliates - Additional Information (Details) $ in Millions | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2024 USD ($) yr affiliate | Jun. 30, 2024 USD ($) | Sep. 30, 2023 USD ($) | Sep. 30, 2024 USD ($) yr affiliate | Sep. 30, 2023 USD ($) | Dec. 31, 2023 affiliate
Estimated Future Amortization Expense of Finite-Lived Intangibles |  |  |  |  |  |
Number of affiliates | affiliate | 22 |  |  | 22 |  | 22
Acquired Client Relationships |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Amortization of intangible assets | $ 7.3 |  | $ 12.5 | $ 21.8 | $ 37.5 |
Estimated Future Amortization Expense of Finite-Lived Intangibles |  |  |  |  |  |
Finite-lived intangible, future amortization expense, remainder of fiscal year | 7.0 |  |  | 7.0 |  |
Finite-lived intangible, future amortization expense in year one | 25.0 |  |  | 25.0 |  |
Finite-lived intangible, future amortization expense in year two | 25.0 |  |  | 25.0 |  |
Finite-lived intangible, future amortization expense in year three | 25.0 |  |  | 25.0 |  |
Finite-lived intangible, future amortization expense in year four | 25.0 |  |  | 25.0 |  |
Finite-lived intangible, future amortization expense in year five | $ 15.0 |  |  | $ 15.0 |  |
Equity Method Investee |  |  |  |  |  |
Estimated Future Amortization Expense of Finite-Lived Intangibles |  |  |  |  |  |
Impairment expense |  | $ 39.9 |  |  |  |
Equity Method Investee | Measurement Input, Growth Rate Period |  |  |  |  |  |
Estimated Future Amortization Expense of Finite-Lived Intangibles |  |  |  |  |  |
Equity method investment, measurement input | yr | 10 |  |  | 10 |  |
Equity Method Investee | Measurement Input, Growth Rate |  |  |  |  |  |
Estimated Future Amortization Expense of Finite-Lived Intangibles |  |  |  |  |  |
Equity method investment, measurement input | (0.025) |  |  | (0.025) |  |
Equity Method Investee | Measurement Input, Long-Term Growth Rate |  |  |  |  |  |
Estimated Future Amortization Expense of Finite-Lived Intangibles |  |  |  |  |  |
Equity method investment, measurement input | 0.03 |  |  | 0.03 |  |
Equity Method Investee | Measurement Input, Discount Rate, Asset Based Fees |  |  |  |  |  |
Estimated Future Amortization Expense of Finite-Lived Intangibles |  |  |  |  |  |
Equity method investment, measurement input | 0.12 |  |  | 0.12 |  |
Equity Method Investee | Measurement Input, Discount Rate, Performance Based Fees |  |  |  |  |  |
Estimated Future Amortization Expense of Finite-Lived Intangibles |  |  |  |  |  |
Equity method investment, measurement input | 0.20 |  |  | 0.20 |  |
Equity Method Investee | Measurement Input, Market Participant Tax Rates |  |  |  |  |  |
Estimated Future Amortization Expense of Finite-Lived Intangibles |  |  |  |  |  |
Equity method investment, measurement input | 0.21 |  |  | 0.21 |  |
Equity Method Investee | Acquired Client Relationships |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Amortization of intangible assets | $ 22.7 |  | $ 21.2 | $ 64.4 | $ 63.0 |
Estimated Future Amortization Expense of Finite-Lived Intangibles |  |  |  |  |  |
Finite-lived intangible, future amortization expense, remainder of fiscal year | 23.0 |  |  | 23.0 |  |
Finite-lived intangible, future amortization expense in year one | 75.0 |  |  | 75.0 |  |
Finite-lived intangible, future amortization expense in year two | 70.0 |  |  | 70.0 |  |
Finite-lived intangible, future amortization expense in year three | 70.0 |  |  | 70.0 |  |
Finite-lived intangible, future amortization expense in year four | 60.0 |  |  | 60.0 |  |
Finite-lived intangible, future amortization expense in year five | $ 45.0 |  |  | $ 45.0 |  |

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