Description of Business and Summary of Significant Accounting Policies (Segment Reporting) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2017 USD ($) ProductService_Groups	Mar. 31, 2016 USD ($)
Accounting Policies [Abstract]
Total revenue, international percentage	34.00%	25.70%
Number of product/service groups | ProductService_Groups	4
Segment Reporting Information [Line Items]
Document Period End Date	Mar. 31, 2017
Operating revenue	$ 79,103	$ 71,066
Exchanges [Member]
Segment Reporting Information [Line Items]
Operating revenue	52,614	50,086
Broker Systems [Member]
Segment Reporting Information [Line Items]
Operating revenue	3,788	3,212
RCS [Member]
Segment Reporting Information [Line Items]
Operating revenue	21,852	16,751
Carrier Systems [Member]
Segment Reporting Information [Line Items]
Operating revenue	$ 849	$ 1,017