Equity Compensation (Details) (Stock options, USD $)
3 Months Ended 0 Months Ended
Mar. 31, 2015
Jan. 01, 2015
Jun. 11, 2013
Shares Subject to Options Outstanding      
Balance at the beginning of the period (in shares) 4,851,221 4,851,221  
Granted (in shares) 41,000    
Exercised (in shares) (96,990)    
Expired (in shares) (5,074)    
Forfeited (in shares) (14,081)    
Balance at the end of the period (in shares) 4,776,076    
Exercisable options (in shares) 2,721,289    
Vested and expected to vest at the end of the period (in shares) 4,596,162    
Weighted Average Grant Date Fair Value      
Granted (in dollars per share) $ 6.87    
Weighted Average Exercise Price      
Balance at the beginning of the period (in dollars per share) $ 10.57 10.57  
Granted (in dollars per share) $ 13.14    
Exercised (in dollars per share) $ 5.05    
Expired (in dollars per share) $ 11.41    
Forfeited (in dollars per share) $ 12.35    
Balance at the end of the period (in dollars per share) $ 10.70    
Exercisable options at the end of the period (in dollars per share) $ 7.49    
Vested and expected to vest (in dollars per share) $ 10.50    
Weighted-Average Remaining Contractual Life      
Exercisable options 5 years 8 months 12 days    
Vested and expected to vest 6 years 10 months 24 days    
2013 Plan
     
Stock options      
Annual increase in shares authorized for issuance as a percentage of shares outstanding as of the preceding December 31     5.00%
Increase in number of shares authorized for issuance   1,215,269