Condensed Consolidated Statements of Operations (Unaudited) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Revenues:
Commissions	$ 324,832	$ 308,438	$ 623,536	$ 579,785
Principal transactions	85,349	83,686	173,346	183,431
Real estate management services	39,823	37,930	79,161	41,891
Fees from related parties	12,242	13,494	25,390	26,041
Market data	3,643	3,990	7,768	8,954
Software solutions	2,530	2,487	5,096	4,936
Interest income	1,651	1,543	3,199	3,738
Other revenues	1,174	622	2,005	831
Gain on divestiture	723,147		723,147
Losses on equity investments	(1,224)	(2,652)	(4,512)	(5,108)
Total revenues	1,193,167	449,538	1,638,136	844,499
Expenses:
Compensation and employee benefits	765,679	308,029	1,055,071	554,898
Allocations of net income to limited partnership units and founding/working partner units	46,084	1,909	53,522	7,889
Total compensation and employee benefits	811,763	309,938	1,108,593	562,787
Occupancy and equipment	37,340	39,092	76,567	75,321
Fees to related parties	2,286	3,169	5,129	6,688
Professional and consulting fees	11,367	19,515	26,308	38,834
Communications	22,755	21,402	47,096	43,360
Selling and promotion	23,239	23,513	43,554	42,959
Commissions and floor brokerage	6,397	5,833	12,168	11,513
Interest expense	9,989	7,578	19,689	15,136
Other expenses	59,780	15,048	77,084	24,539
Total expenses	984,916	445,088	1,416,188	821,137
Income from operations before income taxes	208,251	4,450	221,948	23,362
Provision for income taxes	78,711	70	81,806	7,272
Consolidated net income	129,540	4,380	140,142	16,090
Less: Net income attributable to noncontrolling interest in subsidiaries	95,074	2,422	98,678	5,943
Net income available to common stockholders	34,466	1,958	41,464	10,147
Basic earnings per share
Net income available to common stockholders	34,466	1,958	41,464	10,147
Basic earnings per share	$ 0.20	$ 0.01	$ 0.25	$ 0.07
Basic weighted-average shares of common stock outstanding	171,758	140,368	167,515	138,257
Fully diluted earnings per share
Net income for fully diluted shares	$ 69,944	$ 3,878	$ 89,485	$ 19,668
Fully diluted earnings per share	$ 0.18	$ 0.01	$ 0.24	$ 0.07
Fully diluted weighted-average shares of common stock outstanding	378,092	274,756	367,582	269,482
Dividends declared per share of common stock	$ 0.12	$ 0.17	$ 0.24	$ 0.34
Dividends declared and paid per share of common stock	$ 0.12	$ 0.17	$ 0.24	$ 0.34