Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Revenues:
Trading income, net	$ 166,547	$ 169,792	$ 352,836	$ 383,722
Interest and dividends income	5,422	9,415	9,690	14,597
Technology services	2,212	2,772	4,293	5,188
Total revenue	174,181	181,979	366,819	403,507
Operating Expenses:
Brokerage, exchange and clearance fees, net	55,573	56,501	115,298	117,639
Communication and data processing	17,953	17,549	35,675	35,492
Employee compensation and payroll taxes	20,809	15,165	43,366	42,065
Interest and dividends expense	14,097	16,841	27,634	26,407
Operations and administrative	5,891	6,669	10,810	15,160
Depreciation and amortization	7,800	8,186	15,527	17,849
Amortization of purchased intangibles and acquired capitalized software	53	53	106	106
Charges related to share-based compensation at IPO	516	44,194	1,111	44,194
Financing interest expense on senior secured credit facility	7,075	7,259	14,176	14,861
Total operating expenses	129,767	172,417	263,703	313,773
Income before income taxes and noncontrolling interest	44,414	9,562	103,116	89,734
Provision for income taxes	5,128	1,997	12,474	4,725
Net income	39,286	7,565	90,642	85,009
Noncontrolling interest	(30,908)	(7,091)	(71,916)	(84,535)
Net income available for common stockholders	$ 8,378	$ 474	$ 18,726	$ 474
Earnings per share
Basic (in dollars per share)	$ 0.21	$ 0.01	$ 0.48	$ 0.01
Diluted (in dollars per share)	$ 0.21	$ 0.01	$ 0.48	$ 0.01
Weighted average common shares outstanding
Basic (in shares)	38,230,684	34,305,052	38,220,390	34,305,052
Diluted (in shares)	38,230,684	34,529,349	38,220,390	34,529,349
Dividends declared per share of common stock	$ 0.24		$ 0.48
Comprehensive income
Net income	$ 39,286	$ 7,565	$ 90,642	$ 85,009
Other comprehensive income (loss)
Foreign exchange translation adjustment, net of taxes	(1,230)	1,632	1,264	(3,001)
Comprehensive income	38,056	9,197	91,906	82,008
Less: Comprehensive income attributable to non-controlling interests	(30,024)	(8,311)	(72,825)	(81,122)
Comprehensive income attributable to common stockholders	$ 8,032	$ 886	$ 19,081	$ 886