Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues:
Trading income, net	$ 757,455	$ 685,150	$ 623,733
Interest and dividends income	28,136	27,923	31,090
Technology services	10,622	9,980	9,682
Total revenue	796,213	723,053	664,505
Operating Expenses:
Brokerage, exchange and clearance fees, net	232,469	230,965	195,146
Communication and data processing	68,647	68,847	64,689
Employee compensation and payroll taxes	88,026	84,531	78,353
Interest and dividends expense	52,423	47,083	45,196
Operations and administrative	25,991	21,923	27,215
Depreciation and amortization	33,629	30,441	23,922
Amortization of purchased intangibles and acquired capitalized software	211	211	1,011
Acquisition related retention bonus		2,639	6,705
Debt issue cost related to debt refinancing			10,022
Initial public offering fees and expenses		8,961
Transaction advisory fees and expenses		3,000
Reserve for legal matter	5,440
Charges related to share-based compensation at IPO	44,194
Financing interest expense on senior secured credit facility	29,254	30,894	24,646
Total operating expenses	580,284	529,495	476,905
Income before income taxes and noncontrolling interest	215,929	193,558	187,600
Provision for income taxes	18,439	3,501	5,397
Net income	197,490	190,057	182,203
Noncontrolling interest	(176,603)
Net income available for common stockholders	$ 20,887
Earnings per share
Basic (in dollars per share)	$ 0.60
Diluted (in dollars per share)	$ 0.59
Weighted average common shares outstanding
Basic (in shares)	34,964,312
Diluted (in shares)	35,339,585
Comprehensive income
Net income	$ 197,490	190,057	182,203
Other comprehensive income (loss)
Foreign exchange translation adjustment, net of taxes	(4,255)	(5,032)	1,382
Comprehensive income	193,235	$ 185,025	$ 183,585
Less: Comprehensive income attributable to non-controlling interests	(172,249)
Comprehensive income attributable to common stockholders	$ 20,986