Segment Operating Results - (Footnotes) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Segment Reporting Information [Line Items]
Other Revenue, net	$ (943)	$ 1,227	$ (1,980)	$ (115)
Special Charges	21,507	0	21,507	0
Acquisition and Transition Costs	377	(329)	377	(329)
Total Other Expenses	41,378	23,835	22,399	58,945
Investment Banking [Member]
Segment Reporting Information [Line Items]
Other Revenue, net	(1,122)	983	(2,290)	70
Interest expense on Notes Payable, Subordinated Borrowing and Line of Credit	2,425	2,876	5,006	4,354
Amortization of LP Units / Interests and Certain Other Awards	17,102	20,738	(4,269)	52,497
Special Charges	14,400	0	14,400	0
Acquisition and Transition Costs	0	(733)	0	(733)
Fair Value of Contingent Consideration	0	581	0	687
Intangible Asset and Other Amortization	2,392	2,818	4,784	5,981
Total Other Expenses	33,894	23,404	14,915	58,432
Investment Management [Member]
Segment Reporting Information [Line Items]
Other Revenue, net	179	244	310	(185)
Interest expense on Notes Payable, Subordinated Borrowing and Line of Credit				670
Special Charges	7,107	0	7,107	0
Acquisition and Transition Costs	377	404	377	404
Intangible Asset and Other Amortization	0	27	0	109
Total Other Expenses	$ 7,484	$ 431	$ 7,484	$ 513