Annual report pursuant to Section 13 and 15(d)

Stock-Based Payments - Stock Options (Details)

v3.6.0.2
Stock-Based Payments - Stock Options (Details) - USD ($)
 12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Stock-based payments      
Unrecognized compensation costs $ 8,800,000    
Aggregate Intrinsic Value      
Intrinsic value of options exercised 2,400,000    
Cash received from option exercises $ 400,000 $ 400,000 $ 14,000
Stock options      
Stock-based payments      
Vesting period 4 years    
Shares      
Outstanding at beginning of year (in shares) 2,226,698    
Granted (in shares) 739,541    
Exercised (in shares) (250,408)    
Cancelled (in shares) (172,396)    
Outstanding at end of period (in shares) 2,543,435 2,226,698  
Exercisable (in shares) 826,570    
Vested and expected to vest (in shares) 2,543,435    
Weighted Average Exercise Price      
Outstanding at beginning of year (in dollars per share) $ 3.83    
Granted (in dollars per share) 11.95    
Exercised (in dollars per share) 1.59    
Cancelled (in dollars per share) 3.48    
Outstanding at end of period (in dollars per share) 6.44 $ 3.83  
Exercisable (in dollars per share) 3.06    
Vested and expected to vest (in dollars per share) $ 6.44    
Remaining Contractual Life      
Outstanding 8 years 3 months 18 days 8 years 9 months 18 days  
Exercisable 7 years 4 months 24 days    
Vested and expected to vest 8 years 3 months 18 days    
Aggregate Intrinsic Value      
Outstanding $ 14,898,000 $ 11,185,000  
Exercisable 7,520,000    
Vested and expected to vest 14,898,000    
Performance-based stock options      
Stock-based payments      
Additional stock-based compensation expense recorded related to achievement of certain performance-based milestones 200,000 $ 26,000  
Unrecognized compensation costs $ 1,000,000    
Performance-based stock options | Maximum      
Stock-based payments      
Vesting period 6 years    
Performance-based stock options | Advisor      
Shares      
Granted (in shares) 75,000