Description of Business and Summary of Significant Accounting Policies (Segment Reporting) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended												12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2014 ProductService_Groups	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Total revenue, international percentage													31.00%	31.80%	29.30%
Number of product/service groups													4
Operating revenue	$ 60,633	$ 50,808	$ 51,476	$ 51,404	$ 50,847	$ 50,293	$ 51,004	$ 52,566	$ 54,023	$ 53,804	$ 47,716	$ 43,827	$ 214,321	$ 204,710	$ 199,370
Exchanges
Segment Reporting Information [Line Items]
Operating revenue													169,437	163,925	159,678
Broker Systems
Segment Reporting Information [Line Items]
Operating revenue													17,948	18,378	18,612
RCS
Segment Reporting Information [Line Items]
Operating revenue													21,813	15,678	16,140
Carrier Systems
Segment Reporting Information [Line Items]
Operating revenue													$ 5,123	$ 6,729	$ 4,940