Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues:
Commissions	$ 1,994,227	$ 1,931,860	$ 1,307,912
Principal transactions	325,481	313,142	253,951
Real estate management services	196,801	187,118	163,227
Fees from related parties	24,200	25,348	28,379
Data, software and post-trade	54,309	102,371	11,565
Interest income	12,271	10,643	7,313
Other revenues	5,334	9,957	17,232
Total revenues	2,612,623	2,580,439	1,789,579
Expenses:
Compensation and employee benefits	1,653,613	1,696,622	1,124,516
Allocations of net income and grant of exchangeability to limited partnership units and FPUs	192,934	259,639	136,633
Total compensation and employee benefits	1,846,547	1,956,261	1,261,149
Occupancy and equipment	199,848	218,026	154,854
Fees to related parties	23,864	18,755	12,623
Professional and consulting fees	60,920	66,382	52,598
Communications	124,080	120,427	83,184
Selling and promotion	97,852	97,437	72,032
Commissions and floor brokerage	37,913	35,094	19,349
Interest expense	57,637	69,359	37,945
Other expenses	83,868	138,199	151,065
Total expenses	2,532,529	2,719,940	1,844,799
Other income (losses) , net:
Gain (loss) on divestiture and sale of investments	7,044	394,347
Gains (losses) on equity method investments	3,543	2,597	(7,969)
Other income (loss)	97,579	123,168	49,427
Total other income (losses), net	108,166	520,112	41,458
Income (loss) from operations before income taxes	188,260	380,611	(13,762)
Provision (benefit) for income taxes	60,252	120,496	651
Consolidated net income (loss)	128,008	260,115	(14,413)
Less: Net income (loss) attributable to noncontrolling interest in subsidiaries	25,531	138,797	(11,363)
Net income (loss) available to common stockholders	102,477	121,318	(3,050)
Basic earnings (loss) per share
Net income (loss) available to common stockholders	$ 102,477	$ 121,318	$ (3,050)
Basic earnings (loss) per share	$ 0.37	$ 0.50	$ (0.01)
Basic weighted-average shares of common stock outstanding	277,073	243,460	220,697
Fully diluted earnings (loss) per share
Net income (loss) for fully diluted shares	$ 157,695	$ 161,596	$ (3,050)
Fully diluted earnings (loss) per share	$ 0.36	$ 0.48	$ (0.01)
Fully diluted weighted-average shares of common stock outstanding	433,226	335,387	220,697
Dividends declared per share of common stock	$ 0.62	$ 0.54	$ 0.48
Dividends declared and paid per share of common stock	$ 0.62	$ 0.54	$ 0.48