Segment Reporting - Revenue by Product Group (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenues
Total revenues	$ 128,477		$ 259,961
Revenue in Analytics for functionality but not a separate performance obligation from products and services provided by Workflow Technology and Execution Services	600		1,100
Execution Services
Revenues
Total revenues	89,959		184,315
Workflow Technology
Revenues
Total revenues	27,112		53,687
Analytics
Revenues
Total revenues	11,026		21,065
Corporate
Revenues
Total revenues	$ 380		$ 894
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Revenues
Total revenues		$ 121,581		$ 242,416
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Execution Services
Revenues
Total revenues		86,797		173,084
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Workflow Technology
Revenues
Total revenues		23,352		46,452
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Analytics
Revenues
Total revenues		11,057		22,200
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Corporate
Revenues
Total revenues		$ 375		$ 680