XML 66 R50.htm IDEA: XBRL DOCUMENT v3.3.1.900
Stock-Based Compensation - FV of employee stock options (Details) - USD ($)
 12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Compensation expense      
Total employee, director and non-employee stock-based compensation expense $ 4,869,000 $ 1,861,000 $ 198,000
Employee stock options      
Weighted average assumptions for estimated fair value of employee stock options      
Common stock fair value per share (in dollars per share)     $ 5.50
Common stock fair value per share minimum 11.82 8.56  
Common stock fair value per share maximum 22.35 16.52  
Expected volatility, low end of range (as a percent) 69.17%    
Expected volatility, high end of range (as a percent) 86.46%    
Expected volatility (as a percent)   77.40% 86.70%
Risk-free interest rate, low end of range (as a percent) 1.44% 1.67% 0.90%
Risk-free interest rate, high end of range (as a percent) 1.84% 1.96% 2.10%
Expected term (years)   6 years 6 years
Compensation expense      
Unamortized compensation expense related to unvested options $ 10,800,000 $ 7,600,000  
Period to recognize unamortized compensation expense 2 years 8 months 27 days    
Employee stock options | Minimum      
Weighted average assumptions for estimated fair value of employee stock options      
Expected term (years) 5 years 2 months 23 days    
Employee stock options | Maximum      
Weighted average assumptions for estimated fair value of employee stock options      
Expected term (years) 6 years 29 days    
Employee Stock Purchase Plan      
Weighted average assumptions for estimated fair value of employee stock options      
Expected volatility, low end of range (as a percent) 67.80%    
Expected volatility, high end of range (as a percent) 82.90%    
Risk-free interest rate, low end of range (as a percent) 0.07%    
Risk-free interest rate, high end of range (as a percent) 0.93%    
Compensation expense      
Unamortized compensation expense related to unvested options $ 395,000 $ 204,000  
Employee Stock Purchase Plan | Minimum      
Weighted average assumptions for estimated fair value of employee stock options      
Expected volatility, low end of range (as a percent)   70.60%  
Risk-free interest rate, low end of range (as a percent)   0.06%  
Expected term (years) 6 months 6 months  
Employee Stock Purchase Plan | Maximum      
Weighted average assumptions for estimated fair value of employee stock options      
Expected volatility, high end of range (as a percent)   71.80%  
Risk-free interest rate, high end of range (as a percent)   0.46%  
Expected term (years) 2 years 2 years  
General and administrative      
Compensation expense      
Total employee, director and non-employee stock-based compensation expense $ 2,218,000 $ 848,000 $ 40,000
Research and development      
Compensation expense      
Total employee, director and non-employee stock-based compensation expense $ 2,650,000 $ 1,013,000 $ 158,000