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Goodwill and Acquired Client Relationships - Additional Information (Details) | 1 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | ---
Sep. 30, 2023 USD ($) | Sep. 30, 2023 USD ($) | Dec. 31, 2023 USD ($) | Dec. 31, 2022 USD ($) | Dec. 31, 2021 USD ($)
Intangible assets |  |  |  |  |
Goodwill impairment |  | $ 0 |  |  |
Estimated Future Amortization Expense of Finite-Lived Intangibles |  |  |  |  |
Cash received in Veritable Transaction | $ 287,400,000 |  |  |  |
Affiliate Transaction gain | $ 133,100,000 |  |  |  |
Third Party |  |  |  |  |
Estimated Future Amortization Expense of Finite-Lived Intangibles |  |  |  |  |
Subsidiary, ownership percentage sold | 1 | 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 |  |  | 48,300,000 | $ 49,100,000 |
Estimated Future Amortization Expense of Finite-Lived Intangibles |  |  |  |  |
Intangible future amortization expense in 2024 |  |  | 30,000,000 |  |
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 |  |
Impairment of definite-lived intangible assets |  |  | 0 |  |
Acquired Client Relationships | Intangible Amortization and Impairments |  |  |  |  |
Intangible assets |  |  |  |  |
Amortization and impairment expenses of intangible assets |  |  | $ 48,300,000 | $ 49,100,000 | $ 35,700,000

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- Definition The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 45 -Paragraph 28 -Subparagraph (b) -SubTopic 10 -Topic 230 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482740/230-10-45-28 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 45 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482686/350-30-45-2 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(2) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482665/350-30-50-2 + Details
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- Definition Amount of gain (loss) from sale and disposal of integrated set of activities and assets capable of being conducted and managed for purpose of providing return in form of dividend, lower cost, or other economic benefit to investor, owner, member and participant. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 230 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 28 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482740/230-10-45-28 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 810 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 1B -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481203/810-10-50-1B + Details
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