Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities:
Net income (loss)	$ (12,395)	$ 58,975	$ 182,780
Adjustments to reconcile net income (loss) to net cash provided by / (used in) operating activities:
Depreciation and amortization	12,713	9,498	10,188
Net gain on sale of divested business	(15,638)	0	0
Amortization of Debt Issue Costs	1,208	1,163	692
Amortization of debt discount	6,885	6,302	4,685
Tax benefits from share based payment arrangements	(822)	3,806	1,324
Share-based compensation	26,039	21,740	18,297
Deferred tax benefit	(21,274)	(17,966)	(130,724)
Deferred rent obligations	(880)	(2,333)	(2,348)
Net loss on disposal of fixed assets	0	54	1,575
Net gain on disposal of capital lease	0	0	(1,261)
Goodwill Impairment	0	0	2,334
Contingent liability adjustment	2,139	(200)	(2,055)
Purchases of securities owned, at fair value	(4,483,975)	(5,856,112)	(4,722,554)
Proceeds from sales of securities owned, at fair value	4,447,094	6,039,719	4,272,785
Proceeds from sales of securities sold, not yet purchased, at fair value	3,016,934	2,730,939	1,992,965
Payments to cover securities sold, not yet purchased, at fair value	(3,054,869)	(2,674,153)	(1,898,102)
Net (gains) losses on securities, derivatives and other investments	(28,878)	(34,495)	(97,013)
Consolidated Funds
Purchases of securities owned, at fair value	(113,653)	(25,000)	0
Proceeds from sales of securities owned, at fair value	73,011	0	0
Proceeds from sales of securities sold, not yet purchased, at fair value	2,226	0	0
Payments to cover securities sold, not yet purchased, at fair value	(1,799)	0	0
Purchases of other investments	(221,897)	(92,305)	(19,736)
Proceeds from sales of other investments	17,116	31,417	34,225
Net realized and unrealized (gains) losses on investments and other transactions	(17,402)	(13,552)	(16,386)
(Increase) decrease in operating assets:
Cash at deconsolidated entity	0	0	(784)
Cash collateral pledged	(3,257)	(1,779)	2,601
Securities owned, at fair value, held at broker dealer	(17,005)	14,877	(3,939)
Receivable on derivative contracts, at fair value	16,717	10,259	(4,092)
Securities borrowed	0	676,100	251,673
Receivable from brokers	29,921	(27,750)	(15,533)
Fees receivable, net of allowance	(12,632)	11,099	(1,406)
Due from related parties	(176)	(13,344)	(109)
Other assets	(10,048)	4,580	(13,687)
Consolidated Funds
Cash and cash equivalents	(3,827)	(13,433)	1,547
Receivable on derivative contracts, at fair value	(893)	0	0
Receivable from brokers	(5,978)	0	0
Other assets	152	770	4,187
Increase (decrease) in operating liabilities:
Securities sold, not yet purchased, at fair value, held at broker dealer	7,160	(11,747)	(21,633)
Payable for derivative contracts, at fair value	(421)	(20,147)	(2,055)
Securities loaned	0	(682,493)	(236,084)
Payable to brokers	78,520	(204,186)	258,587
Compensation payable	(60,279)	5,540	78,264
Fees payable	(2,366)	(693)	(129)
Due to related parties	244	(145)	92
Accounts payable, accrued expenses and other liabilities	(8,891)	(3,112)	7,375
Consolidated Funds
Contributions received in advance	1,150	850	0
Payable to brokers	3,699	0	0
Payable for derivative contracts, at fair value	572	0	0
Due to related parties	453	3	0
Accounts payable, accrued expenses and other liabilities	528	(98)	(327)
Net cash provided by / (used in) operating activities	(354,774)	(67,352)	(63,781)
Cash flows from investing activities:
Purchases of other investments	(33,786)	(14,149)	(81,597)
Purchase of business, net of cash acquired (Note 2)	(6,258)	(38,416)	0
Cash convertible note economic hedge transaction	0	0	(35,710)
Proceeds from sales of other investments	54,068	58,166	82,072
Loans issued	0	(46,000)	0
Proceeds from loans held for investments	42,800	0	0
Proceeds from Divestiture of Businesses, Net of Cash Divested	17,303	0	0
Purchase of fixed assets	(15,613)	(7,030)	(2,224)
Net cash provided by / (used in) investing activities	58,514	(47,429)	(37,459)
Cash flows from financing activities:
Securities Sold under Agreements to Repurchase	0	0	(3,657)
Proceeds from issuance of convertible debt	0	0	149,500
Proceeds from Issuance of Preferred Stock, net of issuance costs	0	117,194	0
Capped call option transaction	0	(15,878)	0
Deferred debt issuance costs	0	0	(6,650)
Proceeds from sale of warrant	0	0	15,218
Borrowings on notes and other debt	30,638	7,140	65,392
Repayments on notes and other debt	(29,800)	(3,299)	(3,627)
Income tax effect from share-based payment arrangements	(822)	3,806	1,324
Proceeds from Stock Options Exercised	0	394	116
Purchase of treasury stock	(7,654)	(48,678)	(26,038)
Cash paid to acquire net assets (contingent liability payment)	(2,358)	(1,725)	(800)
Capital contributions by redeemable non-controlling interests in operating entities	10	5,644	705
Capital withdrawals to redeemable non-controlling interests in operating entities	(6,995)	(13,860)	(8,279)
Consolidated Funds
Capital contributions by redeemable non-controlling interests in Consolidated Funds	276,914	104,533	9,736
Capital withdrawals to redeemable non-controlling interests in Consolidated Funds	(10,144)	(11,514)	(16,911)
Net cash provided by / (used in) financing activities	249,789	143,757	176,029
Change in cash and cash equivalents	(46,471)	28,976	74,789
Cash and cash equivalents at beginning of period	158,485	129,509	54,720
Cash and cash equivalents at end of period	112,014	158,485	129,509
Cash paid during the year for interest	17,540	17,525	32,032
Cash paid during the year for taxes	5,085	4,161	547
Supplemental information
Purchase of treasury stock, at cost, through net settlement (See Note 20)	8,835	8,907	5,649
Notes payable increase through asset acquisition	7,164	0	0
Preferred stock dividends declared (See Note 20)	6,792	4,075	0
Cash conversion option (see Note 5)	0	0	35,710
Net assets (liabilities) acquired upon acquisition (net of cash) (See Note 2)	0	(22,468)	0
Common stock issuance upon close of acquisition (see Note 2)	0	3,008	0
Assets acquired under capital lease	0	0	4,075
Net Assets of Deconsolidated Entity	$ 73,042	$ 0	$ 1,544