Equity Compensation (Details 4) (Stock options, USD $)
3 Months Ended
Mar. 31, 2014
Mar. 31, 2013
Total stock-based compensation expense    
Total stock-based compensation expense $ 1,247,000 $ 838,000
Total unrecognized compensation cost related to non-vested stock option awards 17,400,000  
Weighted-average period over which unrecognized compensation cost will be recognized 3 years 3 months 18 days  
Cost of revenue
   
Total stock-based compensation expense    
Total stock-based compensation expense 20,000 16,000
Research and development
   
Total stock-based compensation expense    
Total stock-based compensation expense 478,000 236,000
Sales and marketing
   
Total stock-based compensation expense    
Total stock-based compensation expense 222,000 184,000
General and administrative
   
Total stock-based compensation expense    
Total stock-based compensation expense $ 527,000 $ 402,000