Description of Business and Summary of Significant Accounting Policies (Segment Reporting) (Details) $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Sep. 30, 2014 USD ($)	Jun. 30, 2014 USD ($)	Mar. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Sep. 30, 2013 USD ($)	Jun. 30, 2013 USD ($)	Mar. 31, 2013 USD ($)	Dec. 31, 2015 USD ($) ProductService_Groups	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Segment Reporting Information [Line Items]
Total revenue, international percentage													22.70%	31.00%	31.80%
Number of product/service groups | ProductService_Groups													4
Operating revenue	$ 70,204	$ 66,813	$ 64,712	$ 63,753	$ 60,633	$ 50,808	$ 51,476	$ 51,404	$ 50,847	$ 50,293	$ 51,004	$ 52,566	$ 265,482	$ 214,321	$ 204,710
Exchanges
Segment Reporting Information [Line Items]
Operating revenue													190,746	169,437	163,925
Broker Systems
Segment Reporting Information [Line Items]
Operating revenue													14,481	17,948	18,378
RCS
Segment Reporting Information [Line Items]
Operating revenue													55,917	21,813	15,678
Carrier Systems
Segment Reporting Information [Line Items]
Operating revenue													$ 4,338	$ 5,123	$ 6,729