Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues:
Trading income, net	$ 2,493,248	$ 912,316	$ 1,266,682
Interest and dividends income	62,119	108,778	87,508
Commissions, net and technology services	600,510	498,544	184,339
Other, net	83,454	(2,146)	340,189
Total revenue	3,239,331	1,517,492	1,878,718
Operating Expenses:
Brokerage, exchange, clearance fees and payments for order flow, net	758,843	386,888	376,424
Communication and data processing	213,750	209,393	176,120
Employee compensation and payroll taxes	393,536	383,713	215,556
Interest and dividends expense	125,649	158,039	141,814
Operations and administrative	94,558	103,642	66,769
Depreciation and amortization	66,741	65,644	61,154
Amortization of purchased intangibles and acquired capitalized software	74,254	70,595	26,123
Termination of office leases	9,608	66,452	23,357
Debt issue cost related to debt refinancing, prepayment and commitment fees	28,879	41,132	11,727
Transaction advisory fees and expenses	2,941	26,117	11,487
Charges related to share based compensation at IPO	0	0	24
Financing interest expense on long-term borrowings	87,735	121,859	71,800
Total operating expenses	1,856,494	1,633,474	1,182,355
Income (loss) before income taxes and noncontrolling interest	1,382,837	(115,982)	696,363
Provision for (benefit from) income taxes	261,924	(12,277)	76,171
Net income (loss)	1,120,913	(103,705)	620,192
Noncontrolling interest	(471,716)	45,110	(330,751)
Net income (loss) attributable to common stockholders	$ 649,197	$ (58,595)	$ 289,441
Earnings (loss) per share
Basic (in dollars per share)	$ 5.19	$ (0.53)	$ 2.82
Diluted (in dollars per share)	$ 5.16	$ (0.53)	$ 2.78
Weighted average common shares outstanding
Basic (in shares)	121,692,443	113,918,103	100,875,793
Diluted (in shares)	122,332,190	113,918,103	102,089,139
Net income (loss)	$ 1,120,913	$ (103,705)	$ 620,192
Other comprehensive income (loss)
Foreign currency translation adjustment, net of taxes	15,318	(1,475)	(5,127)
Net change in unrealized cash flow hedges gain (loss), net of taxes	(59,019)	0	0
Comprehensive income (loss)	1,077,212	(105,180)	615,065
Less: Comprehensive (income) loss attributable to noncontrolling interest	(452,855)	45,668	(328,697)
Comprehensive income (loss)	$ 624,357	$ (59,512)	$ 286,368