Description of Business and Summary of Significant Accounting Policies (Segment Reporting) (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) ProductService_Groups	Sep. 30, 2015 USD ($)
Accounting Policies [Abstract]
Total revenue, international percentage			27.80%	22.70%
Number of product/service groups | ProductService_Groups			4
Segment Reporting Information [Line Items]
Document Period End Date			Sep. 30, 2016
Operating revenue	$ 74,608	$ 66,813	$ 218,248	$ 195,278
Exchanges [Member]
Segment Reporting Information [Line Items]
Operating revenue	52,016	46,209	151,424	139,712
Broker Systems [Member]
Segment Reporting Information [Line Items]
Operating revenue	3,557	3,812	10,654	11,067
RCS [Member]
Segment Reporting Information [Line Items]
Operating revenue	18,076	15,754	53,489	41,218
Carrier Systems [Member]
Segment Reporting Information [Line Items]
Operating revenue	$ 959	$ 1,038	$ 2,681	$ 3,281