Financial Instruments and Other Inventory Positions Owned and Financial Instruments and Other Inventory Positions Sold, but Not Yet Purchased - Unrealized Gains/(Losses) on Derivative Instruments (Details) - Not Designated as Hedging Instrument - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Derivative Instruments, Gain (Loss)
Unrealized Gain (Loss) on Derivatives Instruments	$ 3,531	$ 478	$ (3,288)
Interest rate derivative contract | Investment banking
Derivative Instruments, Gain (Loss)
Unrealized Gain (Loss) on Derivatives Instruments	(1,317)	(1,786)	(1,407)
Interest rate derivative contract | Institutional brokerage
Derivative Instruments, Gain (Loss)
Unrealized Gain (Loss) on Derivatives Instruments	$ 4,848	$ 2,264	$ (1,881)