Revenue Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenue Information
Total revenues	$ 277,507	$ 259,838	$ 206,649
Transaction revenue
Revenue Information
Total revenues	259,516	241,395	189,353
Forecasts, consulting and other revenue
Revenue Information
Total revenues	$ 17,991	$ 18,443	$ 17,296