Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues:
Trading income, net	$ 665,465	$ 757,455	$ 685,150
Interest and dividends income	26,419	28,136	27,923
Technology services	10,352	10,622	9,980
Other, net	36
Total revenue	702,272	796,213	723,053
Operating Expenses:
Brokerage, exchange and clearance fees, net	221,214	232,469	230,965
Communication and data processing	71,001	68,647	68,847
Employee compensation and payroll taxes	85,295	88,026	84,531
Interest and dividends expense	56,557	52,423	47,083
Operations and administrative	23,039	25,991	21,923
Depreciation and amortization	29,703	33,629	30,441
Amortization of purchased intangibles and acquired capitalized software	211	211	211
Acquisition related retention bonus	0	0	2,639
Amortization expense related to the deferred financing fees	5,579
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	1,755	44,194
Financing interest expense on long-term borrowings	28,327	29,254	30,894
Total operating expenses	522,681	580,284	529,495
Income before income taxes and noncontrolling interest	179,591	215,929	193,558
Provision for income taxes	21,251	18,439	3,501
Net income	158,340	197,490	190,057
Noncontrolling interest	(125,360)	(176,603)
Net income available for common stockholders	$ 32,980	$ 20,887
Earnings per share
Basic (in dollars per share)	$ 0.83	$ 0.60
Diluted (in dollars per share)	$ 0.83	$ 0.59
Weighted average common shares outstanding
Basic (in shares)	38,539,091	34,964,312
Diluted (in shares)	38,539,091	35,339,585
Comprehensive income
Net income	$ 158,340	$ 197,490	190,057
Other comprehensive income (loss)
Foreign exchange translation adjustment, net of taxes	(1,165)	(4,255)	(5,032)
Comprehensive income	157,175	193,235	$ 185,025
Less: Comprehensive income attributable to non-controlling interests	(124,546)	(172,249)
Comprehensive income attributable to common stockholders	$ 32,629	$ 20,986