Segment Operating Results - (Footnotes) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Other Revenue, net	$ 12,095	$ 9,787	$ 14,755	$ (11,201)
Special Charges, Including Business Realignment Costs	0	8,558	0	32,234
Acquisition and Transition Costs	0	98	7	106
Total Other Expenses	0	9,163	7	34,421
Investment Banking [Member]
Segment Reporting Information [Line Items]
Other Revenue, net	11,233	11,039	13,817	(10,553)
Interest expense on Notes Payable	4,306	4,534	8,876	9,376
Amortization of LP Units	0	0	0	1,067
Special Charges, Including Business Realignment Costs	0	8,558	0	32,202
Acquisition and Transition Costs	0	98	7	106
Intangible Asset Amortization	0	507	0	1,014
Total Other Expenses	0	9,163	7	34,389
Investment Management [Member]
Segment Reporting Information [Line Items]
Other Revenue, net	862	(1,252)	938	(648)
Special Charges, Including Business Realignment Costs	0	0	0	32
Total Other Expenses	$ 0	$ 0	$ 0	$ 32