Revenue Information (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Revenue Information      
Total revenues $ 259,838 $ 206,649 $ 133,958
Transaction revenue      
Revenue Information      
Total revenues 241,395 189,353 118,713
Forecasts, consulting and other revenue      
Revenue Information      
Total revenues $ 18,443 $ 17,296 $ 15,245