Goodwill and Intangibles Schedule of Intangible Assets (Details) (Annual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	$ 55,187	$ 53,964
Intangible assets, accumulated amortization (in dollars)	(29,418)	(28,301)
Intangible Assets, Net	25,769	25,663
Amortization of Intangible Assets	5,000	2,700	$ 3,600
Impairment of Intangible Assets, Finite-lived	0	0
Investment Contracts [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	$ 0	3,900
Finite-Lived Intangible Asset, Useful Life	5 years
Intangible assets, accumulated amortization (in dollars)	$ 0	(3,900)
Intangible Assets, Net	0	0
Trade Names [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	9,962	9,712
Intangible assets, accumulated amortization (in dollars)	(9,689)	(8,897)
Intangible Assets, Net	273	815
Customer Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	33,874	29,484
Intangible assets, accumulated amortization (in dollars)	(12,948)	(10,338)
Intangible Assets, Net	20,926	19,146
Customer Contracts [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	$ 800	800
Finite-Lived Intangible Asset, Useful Life	1 year 2 months 12 days
Intangible assets, accumulated amortization (in dollars)	$ (800)	(800)
Intangible Assets, Net	0	0
Noncompete Agreements [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	2,268	1,831
Intangible assets, accumulated amortization (in dollars)	(818)	(172)
Intangible Assets, Net	1,450	1,659
Developed Technology Rights [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	8,283	8,237
Intangible assets, accumulated amortization (in dollars)	(5,163)	(4,194)
Intangible Assets, Net	$ 3,120	4,043
Cowen Equity Finance [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Impairment of Intangible Assets, Finite-lived		$ 900
Minimum | Trade Names [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	1 year
Minimum | Customer Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	3 years
Minimum | Noncompete Agreements [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	3 years
Minimum | Developed Technology Rights [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	3 years
Maximum | Trade Names [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	7 years 6 months
Maximum | Customer Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	14 years
Maximum | Noncompete Agreements [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	5 years
Maximum | Developed Technology Rights [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	10 years
Broker-Dealer | CRT business
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived Intangible Assets Acquired	$ 5,100
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	8 years 1 month 6 days
Broker-Dealer | Minimum | CRT business
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	1 year
Broker-Dealer | Maximum | CRT business
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	9 years