Acquisitions - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands			1 Months Ended	3 Months Ended			9 Months Ended		12 Months Ended
	Jul. 08, 2024	Nov. 01, 2021	Dec. 31, 2021	Sep. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Business Acquisition [Line Items]
Contingent consideration liability				$ 139,600			$ 139,600		$ 217,200
Increase (decrease) in contingent consideration liability related to change in value of consideration payable							$ 2,400	$ 19,236
Common stock, par value				$ 0.01			$ 0.01		$ 0.01
Acquisition-related costs				$ 5,075		$ 116	$ 9,150	134	$ 100
Amundi US
Business Acquisition [Line Items]
Percentage of economic stake	26.10%
Percentage of number of issued and outstanding shares of common Stock	4.90%
Common stock, par value	$ 0.01
USAA AMCO
Business Acquisition [Line Items]
Increase (decrease) in contingent consideration liability related to change in value of consideration payable						2,700		8,700
NEC Acquisition
Business Acquisition [Line Items]
Contingent consideration liability									13,700
Additional payments in cash to acquire business based on revenue growth		$ 35,000
Cash based on revenue growth period		6 years
Contingent payment period one		36 months
Contingent payment period two		48 months
Contingent payment period three		60 months
Contingent payment compensation expense				15,200		1,400	13,700	4,400
WestEnd Acquisition
Business Acquisition [Line Items]
Period of time over which contingent payments will be made			4 years
Contingent consideration liability				139,600			139,600		$ 217,200
Increase (decrease) in contingent consideration liability related to change in value of consideration payable				$ (1,600)		$ 7,600	$ 2,400	$ 10,500
Payments to acquire business					$ 80,000
Period of time over which contingent "catch-up" provisions payments will be made			5 years 6 months
Maximum aggregate earn-out payments			$ 320,000
Maximum annual earn-out payments			$ 80,000
Amundi US Acquisition
Business Acquisition [Line Items]
Date of acquisition agreement	Jul. 08, 2024