Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Cash flows from operating activities:
Net income (loss)	$ 24,048	$ 38,154
Adjustments to reconcile net income (loss) to net cash provided by / (used in) operating activities:
Depreciation and amortization	6,584	7,036
Amortization of debt discount	4,674	3,241
Tax benefits from share based payment arrangements	3,714	0
Share-based compensation	16,211	14,286
Deferred tax benefit	(2,050)	0
Deferred rent obligations	(2,113)	(1,629)
Net loss on disposal of fixed assets	54	311
Purchases of securities owned, at fair value	(4,650,626)	(3,362,237)
Proceeds from sales of securities owned, at fair value	4,556,647	3,013,982
Proceeds from sales of securities sold, not yet purchased, at fair value	2,003,879	1,371,216
Payments to cover securities sold, not yet purchased, at fair value	(1,940,343)	(1,268,348)
Net (gains) losses on securities, derivatives and other investments	(32,719)	(38,181)
Consolidated Funds
Purchases of securities owned, at fair value	(12,000)	0
Purchases of other investments	(78,491)	(19,568)
Proceeds from sales of other investments	18,722	21,367
Net realized and unrealized (gains) losses on investments and other transactions	(6,749)	(11,320)
(Increase) decrease in operating assets:
Cash collateral pledged	(823)	2,045
Securities owned, at fair value, held at broker dealer	20,696	4,300
Receivable on derivative contracts, at fair value	8,290	9,820
Securities borrowed	676,100	(1,393,783)
Receivable from brokers	(26,744)	(28,169)
Fees receivable, net of allowance	(6,952)	1,501
Due from related parties	106	(2,806)
Other assets	(919)	(5,702)
Consolidated Funds
Cash and cash equivalents	(16,124)	1,680
Other assets	780	4,933
Increase (decrease) in operating liabilities:
Securities sold, not yet purchased, at fair value, held at broker dealer	(7,134)	(19,839)
Payable for derivative contracts, at fair value	(15,252)	(12,016)
Securities loaned	(682,493)	1,406,105
Payable to brokers	(7,010)	171,377
Compensation payable	(41,628)	8,636
Fees payable	12,965	3,840
Due to related parties	(154)	31
Accounts payable, accrued expenses and other liabilities	(7,746)	6,521
Consolidated Funds
Contributions received in advance	5,000	0
Due to related parties	1,000	0
Accounts payable, accrued expenses and other liabilities	67	(455)
Net cash provided by / (used in) operating activities	(178,533)	(73,671)
Cash flows from investing activities:
Purchases of other investments	(10,259)	(80,153)
Purchase of business, net of cash acquired	(14,936)	0
Cash convertible note economic hedge transaction	0	(35,710)
Proceeds from sales of other investments	37,368	75,622
Tenant allowance	0	1,240
Purchase of fixed assets	(5,191)	(6,890)
Net cash provided by / (used in) investing activities	6,982	(45,891)
Cash flows from financing activities:
Securities sold under agreement to repurchase	0	(3,657)
Proceeds from issuance of convertible debt	0	149,500
Proceeds from issuance of preferred stock, net of issuance costs	117,194	0
Capped call option transaction	(15,879)	0
Deferred debt issuance cost	0	(3,720)
Proceeds from sale of warrant	0	15,218
Borrowings on notes and other debt	2,140	6,217
Repayments on notes and other debt	(2,655)	(2,913)
Tax benefits from share-based payment arrangements	3,714	0
Proceeds from stock options exercised	395	116
Purchase of treasury stock	(41,697)	(17,327)
Cash paid to acquire net assets (contingent liability payable)	(1,725)	(518)
Capital contributions by redeemable non-controlling interests in operating entities	5,644	705
Capital withdrawals to redeemable non-controlling interests in operating entities	(8,203)	(9,575)
Consolidated Funds
Capital contributions by redeemable non-controlling interests in Consolidated Funds	83,097	9,568
Capital withdrawals to redeemable non-controlling interests in Consolidated Funds	(7,129)	(12,606)
Net cash provided by / (used in) financing activities	134,896	131,008
Change in cash and cash equivalents	(36,655)	11,446
Cash and cash equivalents at beginning of period	129,509	54,720
Cash and cash equivalents at end of period	92,854	66,166
Supplemental information
Purchase of treasury stock, at cost, through net settlement	8,556	5,610
Preferred stock dividends declared	2,358	0
Cash conversion option	0	35,710
Net assets (liabilities) acquired upon acquisition (net of cash)	11,688	0
Common stock issuance upon close of acquisition	$ 3,008	$ 0