Goodwill and Intangible Assets Schedule of Intangible Assets (Details) (USD $)	12 Months Ended							12 Months Ended				12 Months Ended						12 Months Ended				12 Months Ended						12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Investment Contracts	Dec. 31, 2012 Investment Contracts	Dec. 31, 2013 Trade Names	Dec. 31, 2012 Trade Names	Dec. 31, 2013 Trade Names Minimum	Dec. 31, 2013 Trade Names Maximum	Dec. 31, 2013 Customer Relationships	Dec. 31, 2012 Customer Relationships	Dec. 31, 2013 Customer Relationships Minimum	Dec. 31, 2013 Customer Relationships Maximum	Dec. 31, 2013 Customer Contracts	Dec. 31, 2012 Customer Contracts	Dec. 31, 2013 Noncompete agreements and covenants with limiting conditions acquired	Dec. 31, 2012 Noncompete agreements and covenants with limiting conditions acquired	Dec. 31, 2013 Noncompete agreements and covenants with limiting conditions acquired Minimum	Dec. 31, 2013 Noncompete agreements and covenants with limiting conditions acquired Maximum	Dec. 31, 2013 Intellectual property	Dec. 31, 2012 Intellectual property	Dec. 31, 2013 Intellectual property Minimum	Dec. 31, 2013 Intellectual property Maximum	Dec. 31, 2013 ATM Group and Cowen Equity Finance LP [Member]	Dec. 31, 2013 Dahlman Rose & Company, LLC	Dec. 31, 2011 LaBranche and Co Inc. [Member]	Jun. 28, 2011 LaBranche and Co Inc. [Member]	Dec. 31, 2011 Prior transactions [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life				5 years				5 years	7 years 6 months			4 years	10 years	1 year 2 months 12 days				1 year	10 years			3 years	10 years
Intangible assets																								$ 9,900,000	$ 2,800,000		$ 5,100,000
Impairment of Intangible Assets, Finite-lived																										2,900,000		5,200,000
Amortization of Intangible Assets	3,700,000	2,700,000	8,100,000																							1,000,000
Finite-Lived Intangible Assets, Gross	38,704,000	35,929,000		3,900,000	3,900,000	9,612,000	9,572,000			14,744,000	11,974,000			800,000	800,000	2,697,000	2,732,000			6,951,000	6,951,000
Intangible assets, accumulated amortization (in dollars)	(26,610,000)	(22,945,000)		(3,900,000)	(3,900,000)	(7,747,000)	(7,190,000)			(8,375,000)	(6,284,000)			(800,000)	(800,000)	(2,583,000)	(2,576,000)			(3,205,000)	(2,195,000)
Intangible Assets, Net	$ 12,094,000	$ 12,984,000		$ 0	$ 0	$ 1,865,000	$ 2,382,000			$ 6,369,000	$ 5,690,000			$ 0	$ 0	$ 114,000	$ 156,000			$ 3,746,000	$ 4,756,000
Intangible Assets Amortization, Period for Recognition																								8 years 6 months 18 days	4 years 8 months 1 day