Business Segment Information - Summary of Net Revenues Derived From Investment Management, Research and Related Services (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Revenues:
Total revenues	$ 1,238,905	$ 1,152,350	$ 3,637,152	$ 3,355,043
Less: Broker-dealer related Interest expense	13,340	15,203	38,857	48,382
Net revenues	1,225,565	1,137,147	3,598,295	3,306,661
Reportable Segment
Revenues:
Total revenues		1,152,350	3,637,152	3,355,043
Less: Broker-dealer related Interest expense	13,340	15,203	38,857	48,382
Net revenues	1,225,565	1,137,147	3,598,295	3,306,661
Institutions \| Reportable Segment
Revenues:
Total revenues	266,336	161,090	668,579	496,113
Retail \| Reportable Segment
Revenues:
Total revenues	605,547	631,769	1,836,468	1,834,917
Private Wealth Management \| Reportable Segment
Revenues:
Total revenues	338,022	313,191	978,696	909,416
Other \| Reportable Segment
Revenues:
Total revenues	$ 29,000	$ 46,300	$ 153,409	$ 114,597

Amount of interest expense classified as operating and nonoperating. Includes, but is not limited to, cost of borrowing accounted for as interest expense.

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+ Details

- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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+ References + Details