Stockholders' Equity (Details) (USD $)	12 Months Ended				12 Months Ended	1 Months Ended			12 Months Ended
	Dec. 31, 2012 class	Dec. 31, 2011	Dec. 31, 2010	Jun. 28, 2011 LaBranche and Co Inc. [Member]	Dec. 31, 2011 Common Stock	Dec. 31, 2009 Certain non-affiliate members	Aug. 31, 2012 Common Stock Class A	Dec. 31, 2009 Common Stock Class A	Dec. 31, 2012 Common Stock Class A	Dec. 31, 2011 Common Stock Class A	Dec. 31, 2012 Common Stock Class A RCG	Dec. 31, 2011 Common Stock Class A RCG	Dec. 31, 2010 Common Stock Class A RCG	Dec. 31, 2012 Common Stock Class A RCG	Dec. 31, 2012 Common Stock Class A HVB	Dec. 31, 2012 Common Stock Class B	Dec. 31, 2011 Common Stock Class B	Dec. 31, 2012 Preferred Stock
Equity, Class of Stock [Line Items]
Common stock, shares authorized	500,000,000								250,000,000	250,000,000						250,000,000	250,000,000	10,000,000
Common stock, par value (in dollars per share)									$ 0.01	$ 0.01						$ 0.01	$ 0.01	$ 0.01
Shares issued at the consummation of transaction	37,536,826													37,536,826	2,713,882
Number of classes	2
Shares converted at the time of the transaction									15,042,290
Shares issued (in shares)						284,655		17,292,698
Shares issued (value)								$ 82,000,000
Common stock, shares outstanding									112,447,892	114,047,637	16,135,162	25,189,337	33,576,099			0	0
Shares transferred to member's ownership	9,054,175	8,386,762
Conversion ratio, shares of Company's stock issued per share of Acquiree's stock				0.9980
Stock Issued During Period, Shares, Acquisitions					40,850,133
Preferred stock, shares authorized	10,000,000	10,000,000
Common stock repurchase program, maximum authorized amount							15,000,000		35,000,000.0
Treasury Stock [Roll Forward]
Treasury stock, shares, beginning of period									5,346,003
Treasury stock, cost, beginning of period									16,902,000
Treasury stock, average cost per share, beginning of period, in dollars per share									$ 3.16
Shares purchased for minimum tax withholding, shares									1,604,446
Shares purchased for minimum tax withholding, cost	3,988,000	3,631,000	0						3,988,000
Shares purchased for minimum tax withholding, average cost per share, in dollars per share									$ 2.49
Purchase of treasury stock, shares									4,341,771
Purchase of treasury stock, cost									10,838,000
Treasury stock acquired, average cost per share, in dollars per share									$ 2.50
Treasury stock, shares, end of period									11,292,220
Treasury stock, cost, end of period									$ 31,728,000
Treasury stock, average cost per share, end of period, in dollars per share									$ 2.81