Segment Operating Results - (Footnotes) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Segment Reporting Information [Line Items]
Other Revenue, net	$ 8,243	$ 180
Special Charges	1,029	1,897
Acquisition and Transition Costs	108	21
Total Other Expenses	7,366	8,058
Investment Banking [Member]
Segment Reporting Information [Line Items]
Other Revenue, net	6,487	(1,428)
Interest expense on Notes Payable, Subordinated Borrowing and Line of Credit	2,264	2,261
Amortization of LP Units and Certain Other Awards	4,072	3,983
Special Charges	1,029	1,897
Intangible Asset and Other Amortization	2,157	2,157
Total Other Expenses	7,258	8,037
Investment Management [Member]
Segment Reporting Information [Line Items]
Other Revenue, net	1,756	1,608
Acquisition and Transition Costs	108	21
Total Other Expenses	$ 108	$ 21