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Goodwill and Acquired Client Relationships - Additional Information (Details) | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | ---
Sep. 30, 2023 USD ($) | Sep. 30, 2024 USD ($) | Dec. 31, 2024 USD ($) | Dec. 31, 2023 USD ($) | Dec. 31, 2022 USD ($)
Intangible assets |  |  |  |  |
Goodwill impairment |  | $ 0 |  |  |
Estimated Future Amortization Expense of Finite-Lived Intangibles |  |  |  |  |
Cash received in Veritable Transaction | $ 287,400,000 |  |  |  |
Affiliate Transaction gains | $ 133,100,000 |  | $ 0 | $ 133,100,000 | $ 641,900,000
Third Party |  |  |  |  |
Estimated Future Amortization Expense of Finite-Lived Intangibles |  |  |  |  |
Subsidiary, ownership percentage, sold | 1 |  |  |  |
Acquired Client Relationships |  |  |  |  |
Estimated Future Amortization Expense of Finite-Lived Intangibles |  |  |  |  |
Intangible impairments |  |  | 0 |  |
Acquired Client Relationships |  |  |  |  |
Intangible assets |  |  |  |  |
Amortization and impairment expenses of intangible assets |  |  | 29,000,000.0 | $ 48,300,000 | $ 49,100,000
Estimated Future Amortization Expense of Finite-Lived Intangibles |  |  |  |  |
Intangible future amortization expense in 2025 |  |  | 25,000,000 |  |
Intangible future amortization expense in 2026 |  |  | 25,000,000 |  |
Intangible future amortization expense in 2027 |  |  | 25,000,000 |  |
Intangible future amortization expense in 2028 |  |  | 25,000,000 |  |
Intangible future amortization expense in 2029 |  |  | 15,000,000 |  |
Impairment of definite-lived intangible assets |  |  | $ 0 |  |

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