Condensed Consolidated Statements of Financial Condition (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Assets
Cash and cash equivalents	$ 66,166	$ 54,720
Cash collateral pledged	8,862	10,907
Securities owned, at fair value	660,602	311,039
Receivable on derivative contracts, at fair value	35,966	10,075
Securities borrowed	2,321,556	927,773
Other investments	130,584	99,483
Receivable from brokers	95,149	66,980
Fees receivable, net of allowance	43,566	45,067
Due from related parties	29,716	26,910
Fixed assets, net of accumulated depreciation and amortization of $24,437 and $21,853, respectively	27,390	26,999
Goodwill	37,240	37,240
Intangible assets, net of accumulated amortization of $26,189 and $26,610, respectively	9,985	12,094
Other assets	26,622	17,561
Consolidated Funds
Cash and cash equivalents	368	2,048
Other investments	197,001	187,480
Other assets	691	5,624
Total Assets	3,691,464	1,842,000
Liabilities
Securities sold, not yet purchased, at fair value	209,089	130,954
Securities sold under agreement to repurchase	0	3,657
Payable for derivative contracts, at fair value	31,369	7,674
Securities loaned	2,324,682	918,577
Payable to brokers	246,797	75,420
Compensation payable	66,140	51,807
Short-term borrowings and other debt	4,608	2,564
Convertible debt	117,031	0
Fees payable	10,164	6,324
Due to related parties	413	382
Accounts Payable, Accrued Expenses and Other Liabilities	50,774	45,290
Consolidated Funds
Capital withdrawals payable	0	5,222
Accounts payable, accrued expenses and other liabilities	94	549
Total Liabilities	3,061,161	1,248,420
Commitments and Contingencies (Note 13)
Redeemable non-controlling interests	91,429	85,814
Stockholders' equity
Preferred stock, par value $0.01 per share; 10,000,000 shares authorized, no shares issued and outstanding	0	0
Additional paid-in capital	766,961	737,341
(Accumulated deficit) retained earnings	(158,498)	(183,243)
Accumulated other comprehensive income (loss)	272	592
Less: Class A common stock held in treasury, at cost, 21,508,368 and 15,873,549 shares as of September 30, 2014 and December 31, 2013, respectively.	(71,021)	(48,084)
Total Stockholders' Equity	538,874	507,766
Total Liabilities and Stockholders' Equity	3,691,464	1,842,000
Common Stock Class A
Stockholders' equity
Common stock	1,160	1,160
Less: Class A common stock held in treasury, at cost, 21,508,368 and 15,873,549 shares as of September 30, 2014 and December 31, 2013, respectively.	(71,021)	(48,084)
Common Stock Class B
Stockholders' equity
Common stock	$ 0	$ 0