Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash flows from operating activities:
Net income (loss)	$ 58,975	$ 182,780	$ 17,840
Adjustments to reconcile net income (loss) to net cash provided by / (used in) operating activities:
Depreciation and amortization	9,498	10,188	10,227
Amortization of debt discount	6,302	4,685	0
Tax benefits from share based payment arrangements	3,806	1,324	0
Share-based compensation	21,740	18,297	17,915
Deferred tax benefit	(17,966)	(130,724)	0
Deferred rent obligations	(2,333)	(2,348)	(3,770)
Net loss on disposal of fixed assets	54	1,575	410
Net gain on disposal of capital leases	0	(1,261)	0
Goodwill Impairment	0	2,334	0
Contingent liability adjustment	(200)	(2,055)	0
Purchases of securities owned, at fair value	(5,856,112)	(4,722,554)	(6,765,271)
Proceeds from sales of securities owned, at fair value	6,039,719	4,272,785	7,057,506
Proceeds from sales of securities sold, not yet purchased, at fair value	2,730,939	1,992,965	2,740,372
Payments to cover securities sold, not yet purchased, at fair value	(2,674,153)	(1,898,102)	(2,774,696)
Net (gains) losses on securities, derivatives and other investments	(34,495)	(97,013)	(44,741)
Consolidated Funds
Purchases of securities owned, at fair value	(25,000)	0	(298,220)
Proceeds from sales of securities owned, at fair value	0	0	287,412
Proceeds from sales of securities sold, not yet purchased, at fair value	0	0	42,701
Payments to Cover Securities Sold Not Yet Purchased at Fair Value	0	0	(42,387)
Purchases of other investments	(92,305)	(19,736)	(4,497)
Proceeds from sales of other investments	31,417	34,225	56,873
Net realized and unrealized (gains) losses on investments and other transactions	(13,552)	(16,386)	(14,153)
(Increase) decrease in operating assets:
Cash Acquired from Acquisition	0	0	10,747
Cash at deconsolidated entity	0	(784)	0
Cash collateral pledged	(1,779)	2,601	135
Securities owned, at fair value, held at broker dealer	14,877	(3,939)	20,080
Receivable on derivative contracts, at fair value	10,259	(4,092)	10,673
Securities borrowed	676,100	251,673	(521,447)
Receivable from brokers	(27,750)	(15,533)	5,218
Fees receivable, net of allowance	11,099	(1,406)	(9,975)
Due from related parties	(13,344)	(109)	(5,888)
Other assets	5,743	(15,925)	2,818
Consolidated Funds
Cash and cash equivalents	(13,433)	1,547	1,511
Other assets	770	4,187	(5,528)
Increase (decrease) in operating liabilities:
Securities sold, not yet purchased, at fair value, held at broker dealer	(11,747)	(21,633)	(10,994)
Payable for derivative contracts, at fair value	(20,147)	(2,055)	(2,374)
Securities loaned	(682,493)	(236,084)	509,605
Payable to brokers	(204,186)	258,587	(113,023)
Compensation payable	5,540	78,264	(13,036)
Fees payable	(693)	(129)	1,047
Due to related parties	(145)	92	(280)
Accounts payable, accrued expenses and other liabilities	(3,112)	7,375	(13,404)
Consolidated Funds
Contributions received in advance	850	0	0
Payable to brokers	0	0	1,030
Due to related parties	3	0	0
Accounts payable, accrued expenses and other liabilities	(98)	(327)	146
Net cash provided by / (used in) operating activities	(67,352)	(66,711)	150,582
Cash flows from investing activities:
Purchases of other investments	(14,149)	(81,597)	(20,031)
Purchase of business, net of cash acquired	(38,416)	0	0
Cash convertible note economic hedge transaction	0	(35,710)	0
Proceeds from sales of other investments	58,166	82,072	29,890
Loans issued	(46,000)	0	0
Purchase of fixed assets	(7,030)	(2,224)	(1,141)
Net cash provided by / (used in) investing activities	(47,429)	(37,459)	8,718
Cash flows from financing activities:
Securities sold under agreement to repurchase	0	(3,657)	(162,288)
Proceeds from issuance of convertible debt	0	149,500	0
Proceeds from issuance of preferred stock, net of issuance costs	117,194	0	0
Capped call option transaction	(15,878)	0	0
Deferred debt issuance cost	0	(3,720)	0
Proceeds from sale of warrant	0	15,218	0
Borrowings on notes and other debt	7,140	65,392	2,044
Repayments on notes and other debt	(3,299)	(3,627)	(3,613)
Tax benefits from share-based payment arrangements	3,806	1,324	0
Proceeds from stock options exercised	394	116	0
Purchase of treasury stock	(48,678)	(26,038)	(12,732)
Cash paid to acquire net assets (contingent liability payable)	(1,725)	(800)	(779)
Capital contributions by redeemable non-controlling interests in operating entities	5,644	705	501
Capital withdrawals to redeemable non-controlling interests in operating entities	(13,860)	(8,279)	(3,058)
Consolidated Funds
Capital contributions by redeemable non-controlling interests in Consolidated Funds	104,533	9,736	14,680
Capital withdrawals to redeemable non-controlling interests in Consolidated Funds	(11,514)	(16,911)	(22,873)
Net cash provided by / (used in) financing activities	143,757	178,959	(188,118)
Change in cash and cash equivalents	28,976	74,789	(28,818)
Cash and cash equivalents at beginning of period	129,509	54,720	83,538
Cash and cash equivalents at end of period	158,485	129,509	54,720
Supplemental information
Interest Paid	17,525	32,032	24,644
Income Taxes Paid	4,161	547	72
Purchase of treasury stock, at cost, through net settlement	8,907	5,649	3,649
Preferred stock dividends declared	4,075	0	0
Cash conversion option	0	35,710	0
Net assets (liabilities) acquired upon acquisition (net of cash)	22,468	0	0
Common stock issuance upon close of acquisition	3,008	0	6,240
Assets acquired under capital lease	0	4,075	0
Re-issuance of treasury stock for services provided	0	0	65
Net assets transferred to Merger Master	0	0	22,152
Net Assets of Deconsolidated Entity	$ 0	$ 1,544	$ 0