Business Segment Information - Summary of Net Revenues Derived From Investment Management, Research and Related Services (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Revenues:
Total revenues	$ 1,183,516	$ 1,104,569	$ 2,398,247	$ 2,202,693
Less: Broker-dealer related Interest expense	12,512	15,662	25,517	33,179
Net revenues	1,171,004	1,088,907	2,372,730	2,169,514
Reportable Segment
Revenues:
Total revenues		1,104,569	2,398,247	2,202,693
Less: Broker-dealer related Interest expense	12,512	15,662	25,517	33,179
Net revenues	1,171,004	1,088,907	2,372,730	2,169,514
Institutions | Reportable Segment
Revenues:
Total revenues	187,650	163,018	402,243	335,023
Retail | Reportable Segment
Revenues:
Total revenues	617,055	603,176	1,230,921	1,203,148
Private Wealth Management | Reportable Segment
Revenues:
Total revenues	326,913	297,428	640,674	596,225
Other | Reportable Segment
Revenues:
Total revenues	$ 51,898	$ 40,947	$ 124,409	$ 68,297