Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenues:
Commissions	$ 671,318	$ 582,106	$ 1,998,237	$ 1,704,998
Principal transactions	73,360	75,766	250,266	241,869
Gains from mortgage banking activities/originations, net	51,972	45,455	132,764	164,263
Real estate management and other services	101,881	60,798	305,880	163,017
Servicing fees	34,948	29,057	96,207	80,729
Fees from related parties	7,128	7,173	19,989	20,129
Data, software and post-trade	16,547	13,776	47,016	40,185
Interest income	15,946	11,726	37,060	40,909
Other revenues	4,154	1,171	6,557	3,023
Total revenues	977,254	827,028	2,893,976	2,459,122
Expenses:
Compensation and employee benefits	517,865	495,145	1,576,706	1,438,129
Allocations of net income and grant of exchangeability to limited partnership units and FPUs	67,919	48,446	239,696	161,876
Total compensation and employee benefits	585,784	543,591	1,816,402	1,600,005
Occupancy and equipment	58,193	51,962	165,405	153,102
Fees to related parties	9,743	4,380	27,394	16,389
Professional and consulting fees	33,491	24,486	86,490	69,047
Communications	31,693	33,290	100,686	97,816
Selling and promotion	30,850	26,828	93,599	81,503
Commissions and floor brokerage	15,382	10,410	45,100	31,316
Interest expense	33,472	24,425	88,051	69,678
Other expenses	69,706	55,600	204,604	148,262
Total expenses	868,314	774,972	2,627,731	2,267,118
Other income (losses) , net:
Gain (loss) on divestiture and sale of investments		4		561
Gains (losses) on equity method investments	1,344	2,147	9,999	3,986
Other income (loss)	108,776	88,195	141,908	97,928
Total other income (losses), net	110,120	90,346	151,907	102,475
Income (loss) from operations before income taxes	219,060	142,402	418,152	294,479
Provision (benefit) for income taxes	56,756	31,854	108,427	55,084
Consolidated net income (loss)	162,304	110,548	309,725	239,395
Less: Net income (loss) attributable to noncontrolling interest in subsidiaries	42,018	29,019	95,462	68,121
Net income (loss) available to common stockholders	120,286	81,529	214,263	171,274
Basic earnings (loss) per share
Net income (loss) available to common stockholders	$ 118,864	$ 81,529	$ 212,677	$ 171,274
Basic earnings (loss) per share	$ 0.36	$ 0.28	$ 0.67	$ 0.60
Basic weighted-average shares of common stock outstanding	327,932	288,308	319,027	286,200
Fully diluted earnings (loss) per share
Net income (loss) for fully diluted shares	$ 171,720	$ 127,495	$ 310,922	$ 266,001
Fully diluted earnings (loss) per share	$ 0.35	$ 0.28	$ 0.64	$ 0.59
Fully diluted weighted-average shares of common stock outstanding	487,636	457,341	482,711	451,348