Description of Business and Summary of Significant Accounting Policies (Segment Reporting) (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) ProductService_Groups	Jun. 30, 2016 USD ($)
Accounting Policies [Abstract]
Total revenue, international percentage			36.90%	28.20%
Number of product/service groups | ProductService_Groups			4
Segment Reporting Information [Line Items]
Document Period End Date			Jun. 30, 2017
Operating revenue	$ 87,387	$ 72,574	$ 166,490	$ 143,640
Exchanges [Member]
Segment Reporting Information [Line Items]
Operating revenue	60,373	49,322	112,987	99,408
Broker Systems [Member]
Segment Reporting Information [Line Items]
Operating revenue	3,595	3,885	7,383	7,097
RCS [Member]
Segment Reporting Information [Line Items]
Operating revenue	22,663	18,662	44,515	35,413
Carrier Systems [Member]
Segment Reporting Information [Line Items]
Operating revenue	$ 756	$ 705	$ 1,605	$ 1,722