Segment Reporting - Financial Information (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($) segment	Jun. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Segment reporting
Number of operating segments | segment			4
Total Revenues	$ 120,610	$ 140,494	$ 245,278	$ 290,221
Income (loss) before income tax expense (benefit)	(9,658)	(8,949)	(13,296)	13,391
Identifiable assets	1,106,216	1,678,495	1,106,216	1,678,495	$ 1,709,022
Restructuring charge	4,355		4,355
Chief Executive Officer
Segment reporting
Cash and stock awards	500		3,300
Former CEO | Settlement agreement for termination of Former CEO
Segment reporting
Reserve for probable settlement	2,300		4,800
Legal and related costs	2,400		2,700
Loss of Profits Due to Outage of Outsourced Primary Data Centre
Segment reporting
Proceeds from insurer to settle claims			2,400
Settlement with S E C for Investigation into Proprietary Trading Pilot
Segment reporting
Reserve for probable settlement		20,300
Legal and related costs		2,300
U.S. Operations
Segment reporting
Total Revenues	58,574	75,474	124,903	155,928
Income (loss) before income tax expense (benefit)	(2,874)	5,735	(769)	16,791
Identifiable assets	504,998	1,209,355	504,998	1,209,355
Canadian Operations
Segment reporting
Total Revenues	15,790	16,705	31,886	35,617
Income (loss) before income tax expense (benefit)	2,782	3,615	6,120	7,369
Identifiable assets	99,036	96,370	99,036	96,370
European Operations
Segment reporting
Total Revenues	32,203	33,574	63,342	70,180
Income (loss) before income tax expense (benefit)	6,284	7,763	11,963	18,893
Identifiable assets	429,986	286,607	429,986	286,607
Asia Pacific Operations
Segment reporting
Total Revenues	11,280	14,512	22,037	28,034
Income (loss) before income tax expense (benefit)	(93)	1,602	(693)	2,709
Identifiable assets	72,196	86,163	72,196	86,163
Corporate
Segment reporting
Total Revenues	2,763	229	3,110	462
Income (loss) before income tax expense (benefit)	$ (15,757)	$ (27,664)	$ (29,917)	$ (32,371)