Segment Operating Results - (Footnotes) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Other Revenue, net	$ 10,002	$ 9,477	$ (10,801)	$ 17,720
Special Charges, Including Business Realignment Costs	8,558	1,029	32,234	2,058
Acquisition and Transition Costs	98	0	106	108
Total Other Expenses	9,163	6,909	34,421	14,275
Investment Banking [Member]
Segment Reporting Information [Line Items]
Other Revenue, net	11,254	7,236	(10,153)	13,723
Interest expense on Notes Payable and Line of Credit	4,534	2,304	9,376	4,568
Amortization of LP Units and Certain Other Awards	0	3,723	1,067	7,795
Special Charges, Including Business Realignment Costs	8,558	1,029	32,202	2,058
Acquisition and Transition Costs	98	0	106	0
Intangible Asset and Other Amortization	507	2,157	1,014	4,314
Total Other Expenses	9,163	6,909	34,389	14,167
Investment Management [Member]
Segment Reporting Information [Line Items]
Other Revenue, net	(1,252)	2,241	(648)	3,997
Special Charges, Including Business Realignment Costs	0	0	32	0
Acquisition and Transition Costs	0	0	0	108
Total Other Expenses	$ 0	$ 0	$ 32	$ 108