Goodwill and Intangibles Schedule of Intangible Assets (Details) (Annual) - USD ($) $ in Thousands		12 Months Ended
	Jun. 01, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization of Intangible Assets		$ 5,000	$ 6,100	$ 5,000
Intangible assets, accumulated amortization (in dollars)		(38,093)	(33,081)
Intangible Assets, Net		24,943	29,955
Finite-Lived Intangible Assets, Gross		$ 63,036	63,036
Investment Contracts [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life		5 years
Trade Names [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets, accumulated amortization (in dollars)		$ (10,599)	(10,555)
Intangible Assets, Net		23	67
Finite-Lived Intangible Assets, Gross		10,622	10,622
Customer Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets, accumulated amortization (in dollars)		(18,960)	(15,733)
Intangible Assets, Net		22,174	25,401
Finite-Lived Intangible Assets, Gross		$ 41,134	41,134
Customer Contracts [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
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
Finite-Lived Intangible Assets, Gross		800	800
Noncompete Agreements [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets, accumulated amortization (in dollars)		(2,055)	(1,479)
Intangible Assets, Net		182	758
Finite-Lived Intangible Assets, Gross		2,237	2,237
Developed Technology Rights [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets, accumulated amortization (in dollars)		(5,679)	(4,514)
Intangible Assets, Net		2,564	3,729
Finite-Lived Intangible Assets, Gross		8,243	8,243
Convergex Group
Acquired Finite-Lived Intangible Assets [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill	$ 10,300
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	7 years 8 months 12 days
Amortization of Intangible Assets		$ 1,300	$ 1,400
Finite-Lived Intangible Assets, Gross	$ 10,270
Convergex Group | Customer Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	9 years
Minimum | Trade Names [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life		7 months 6 days
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
Minimum | Convergex Group
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	7 months 6 days
Minimum | Convergex Group | Trade Names [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	7 months 6 days
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
Maximum | Convergex Group
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	9 years
Maximum | Convergex Group | Trade Names [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	2 years 7 months 6 days