Segment Operating Results - (Footnotes) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting Information [Line Items]
Other Revenue, net	$ 4,245	$ 5,855	$ 21,965	$ 7,206
Special Charges	1,029	1,967	3,087	3,864
Acquisition and Transition Costs	380	0	488	21
Total Other Expenses	8,117	7,888	22,392	21,826
Investment Banking [Member]
Segment Reporting Information [Line Items]
Other Revenue, net	2,709	4,108	16,432	3,219
Interest expense on Notes Payable, Subordinated Borrowing and Line of Credit	3,786	2,300	8,354	6,861
Amortization of LP Units and Certain Other Awards	4,551	3,764	12,346	11,470
Special Charges	1,029	1,967	3,087	3,864
Acquisition and Transition Costs	180	0	180	0
Intangible Asset and Other Amortization	2,157	2,157	6,471	6,471
Total Other Expenses	7,917	7,888	22,084	21,805
Investment Management [Member]
Segment Reporting Information [Line Items]
Other Revenue, net	1,536	1,747	5,533	3,987
Acquisition and Transition Costs	200	0	308	21
Total Other Expenses	$ 200	$ 0	$ 308	$ 21