Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Revenues:
Commissions	$ 309,542	$ 389,768	$ 666,206	$ 824,988
Principal transactions	88,169	81,997	203,770	180,760
Fees from related parties	3,625	4,245	6,942	8,030
Data, software and post-trade	23,391	21,602	47,518	43,588
Interest and dividend income	8,961	11,455	11,396	14,493
Other revenues	2,068	3,383	6,388	8,167
Total revenues	435,756	512,450	942,220	1,080,026
Expenses:
Compensation and employee benefits	211,873	270,586	469,141	578,929
Equity-based compensation and allocations of net income to limited partnership units and FPUs	46,133	58,290	104,009	91,785
Total compensation and employee benefits	258,006	328,876	573,150	670,714
Occupancy and equipment	39,921	47,159	78,584	95,549
Fees to related parties	6,009	4,518	11,734	9,900
Professional and consulting fees	13,810	20,029	29,441	36,235
Communications	27,166	30,776	55,057	60,586
Selling and promotion	12,443	8,618	23,381	16,106
Commissions and floor brokerage	14,239	14,308	31,582	32,237
Interest expense	14,342	18,680	28,645	36,533
Other expenses	23,010	23,772	40,785	39,809
Total expenses	408,946	496,736	872,359	997,669
Other income (losses), net:
Gains (losses) on divestitures and sale of investments	0	(92)	0	(92)
Gains (losses) on equity method investments	2,729	1,323	5,532	2,789
Other income (loss)	1,909	1,924	1,413	7,330
Total other income (losses), net	4,638	3,155	6,945	10,027
Income (loss) from operations before income taxes	31,448	18,869	76,806	92,384
Provision (benefit) for income taxes	15,105	(1,191)	29,762	13,748
Consolidated net income (loss)	16,343	20,060	47,044	78,636
Less: Net income (loss) attributable to noncontrolling interest in subsidiaries	1,581	3,820	6,310	19,680
Net income (loss) available to common stockholders	14,762	16,240	40,734	58,956
Basic earnings (loss) per share
Net income (loss) available to common stockholders	$ 14,762	$ 16,240	$ 40,734	$ 58,956
Basic earnings (loss) per share (in dollars per share)	$ 0.04	$ 0.04	$ 0.11	$ 0.16
Basic weighted-average shares of common stock outstanding (in shares)	375,613	384,902	371,988	379,639
Fully diluted earnings (loss) per share
Net income (loss) for fully diluted shares	$ 19,710	$ 23,260	$ 53,348	$ 84,963
Fully diluted earnings (loss) per share (in shares)	$ 0.04	$ 0.04	$ 0.11	$ 0.15
Fully diluted weighted-average shares of common stock outstanding (in shares)	507,005	563,923	504,609	560,210