Segment Operating Results - (Footnotes) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Other Revenue, net	$ (469)	$ 722	$ (2,449)	$ 607
Special Charges	0	0	21,507	0
Acquisition and Transition Costs	599	339	976	10
Total Other Expenses	12,240	17,720	34,639	76,665
Investment Banking [Member]
Segment Reporting Information [Line Items]
Other Revenue, net	(535)	200	(2,825)	270
Interest expense on Notes Payable, Subordinated Borrowing and Line of Credit	2,488	2,592	7,494	6,946
Amortization of LP Units / Interests and Certain Other Awards	9,249	13,859	4,980	66,356
Special Charges	0	0	14,400	0
Acquisition and Transition Costs	107	41	107	(692)
Fair Value of Contingent Consideration	0	984	0	1,671
Intangible Asset and Other Amortization	2,392	2,538	7,176	8,519
Total Other Expenses	11,748	17,422	26,663	75,854
Investment Management [Member]
Segment Reporting Information [Line Items]
Other Revenue, net	66	522	376	337
Interest expense on Notes Payable, Subordinated Borrowing and Line of Credit				670
Special Charges	0	0	7,107	0
Acquisition and Transition Costs	492	298	869	702
Intangible Asset and Other Amortization	0	0	0	109
Total Other Expenses	$ 492	$ 298	$ 7,976	$ 811