Segment Operating Results - (Footnotes) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Other Revenue, net	$ 7,476	$ 4,245	$ (3,325)	$ 21,965
Special Charges, Including Business Realignment Costs	7,380	1,029	39,614	3,087
Acquisition and Transition Costs	454	380	560	488
Total Other Expenses	8,003	8,117	42,424	22,392
Investment Banking [Member]
Segment Reporting Information [Line Items]
Other Revenue, net	4,449	2,709	(5,704)	16,432
Interest expense on Notes Payable and Line of Credit	4,218	3,786	13,594	8,354
Amortization of LP Units and Certain Other Awards	0	4,551	1,067	12,346
Special Charges, Including Business Realignment Costs	7,380	1,029	39,582	3,087
Acquisition and Transition Costs	154	180	260	180
Intangible Asset and Other Amortization	169	2,157	1,183	6,471
Total Other Expenses	7,703	7,917	42,092	22,084
Investment Management [Member]
Segment Reporting Information [Line Items]
Other Revenue, net	3,027	1,536	2,379	5,533
Special Charges, Including Business Realignment Costs	0	0	32	0
Acquisition and Transition Costs	300	200	300	308
Total Other Expenses	$ 300	$ 200	$ 332	$ 308