Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Cash flows from operating activities:
Net income (loss)	$ 919	$ 6,236
Adjustments to reconcile net income (loss) to net cash provided by / (used in) operating activities:
Depreciation and amortization	2,553	2,155
Share-based compensation	4,752	5,944
Deferred rent obligations	(4,159)	(664)
Net loss on disposal of fixed assets	97	0
Purchases of securities owned, at fair value	(1,298,853)	(1,643,802)
Proceeds from sales of securities owned, at fair value	1,472,056	1,579,427
Proceeds from sales of securities sold, not yet purchased, at fair value	708,168	967,861
Payments to cover securities sold, not yet purchased, at fair value	(651,829)	(994,775)
Net (gains) losses on securities, derivatives and other investments	(9,129)	(17,866)
Consolidated Funds
Purchases of securities owned, at fair value	(78,792)	(108,768)
Proceeds from sales of securities owned, at fair value	82,320	112,522
Purchases of other investments	(973)	(4,279)
Proceeds from sales of other investments	18,352	7,580
Net realized and unrealized (gains) losses on investments and other transactions	(6,675)	(6,323)
(Increase) decrease in operating assets:
Cash acquired upon transaction	10,747	0
Cash collateral pledged	137	47
Securities owned, at fair value, held at broker dealer	(14,882)	26,836
Securities borrowed	(51,623)	0
Receivable from brokers	19,284	(4,778)
Fees receivable, net of allowance	(1,644)	3,317
Due from related parties	1,478	(724)
Other assets	(5,341)	304
Consolidated Funds
Cash and cash equivalents	(261)	(1,322)
Other assets	(6,407)	1,206
Increase (decrease) in operating liabilities:
Securities sold, not yet purchased, at fair value, held at broker dealer	(8,845)	14,748
Securities loaned	48,895	0
Payable to brokers	(100,082)	(48,314)
Compensation payable	(46,014)	(51,810)
Fees payable	(1,829)	3,134
Due to related parties	(44)	(927)
Accounts payable, accrued expenses and other liabilities	2,482	(3,703)
Consolidated Funds
Due to related parties	0	25
Accounts payable, accrued expenses and other liabilities	(112)	(11)
Net cash provided by / (used in) operating activities	84,746	(156,724)
Cash flows from investing activities:
Securities purchased under agreement to resell	0	35,253
Purchases of other investments	(5,161)	(6,441)
Proceeds from sales of other investments	15,534	9,253
Purchase of fixed assets	(237)	(445)
Net cash provided by / (used in) investing activities	10,136	37,620
Cash flows from financing activities:
Securities sold under agreement to repurchase	(136,704)	65,408
Borrowings on short-term borrowings and other debt	2,044	0
Repayments on short-term borrowings and other debt	(797)	(375)
Purchase of treasury stock	(235)	(905)
Capital withdrawals to non-controlling interests in operating entities	(432)	(2,042)
Consolidated Funds
Capital contributions by non-controlling interests in Consolidated Funds	300	0
Capital withdrawals to non-controlling interests in Consolidated Funds	(5,645)	(3,653)
Net cash provided by / (used in) financing activities	(141,469)	58,433
Change in cash and cash equivalents	(46,587)	(60,671)
Cash and cash equivalents at beginning of year	83,538	126,889
Cash and cash equivalents at end of year	36,951	66,218
Supplemental non-cash information
Non compete agreements and covenants with limiting conditions acquired (see Note 2)	460	0
Common stock issuance upon close of acquisition (see Note 2)	6,297	0
Purchase of treasury stock, at cost, through net settlement (See Note 15)	177	0
Net assets of consolidated entities	0	19,073
Net assets of deconsolidated entities	$ 0	$ 17,104