XML 70 R56.htm IDEA: XBRL DOCUMENT v3.8.0.1
Stock Incentive Plans - Stock Option Plan Activity (Details) - USD ($)
$ / shares in Units, $ in Thousands
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Stock options      
Outstanding at beginning of year (in shares) 2,270,169    
Granted (in shares) 890,740    
Exercised (in shares) (22,879)    
Cancelled or forfeited (in shares) (292,404)    
Outstanding at end of year (in shares) 2,845,626 2,270,169  
Vested and Exercisable to vest at end of year (in shares) 1,265,411    
Weighted-Average Exercise Price      
Outstanding at beginning of year (in dollars per share) $ 6.11    
Granted (in dollars per share) 1.26    
Exercised (in dollars per share) 1.01    
Cancelled or forfeited (in dollars per share) 7.13    
Outstanding at end of year (in dollars per share) 4.53 $ 6.11  
Vested and Exercisable at end of year (in dollars per share) $ 5.91    
Weighted Average Remaining Contractual Term (years)      
Outstanding at end of year 7 years 9 months 8 years 1 month 21 days  
Vested and Exercisable at end of year 6 years 6 months 11 days    
Aggregate Intrinsic Value      
Outstanding at the beginning of the year $ 613    
Outstanding at the end of the year $ 216 $ 613  
Weighted average of the assumptions used to compute employee stock based compensation      
Expected term (in years)   6 years 3 months  
Expected dividend yield (as a percent) 0.00% 0.00% 0.00%
Stock options      
Unrecognized stock-based compensation expense      
Intrinsic value of options exercised $ 40 $ 500 $ 300
Adjusted fair value of options vested $ 2,200 $ 2,300 $ 1,400
Weighted average grant date fair value of options granted (in dollars per share) $ 0.85 $ 2.89 $ 7.68
Unrecognized compensation expense related to unvested stock option awards $ 3,200    
Weighted-average amortization period over which cost is expected to be recognized 2 years    
Minimum      
Weighted average of the assumptions used to compute employee stock based compensation      
Weighted-average expected volatility (as a percent) 76.10% 72.00% 73.60%
Expected term (in years) 6 years 3 months   6 years 2 months 1 day
Risk-free interest rate (as a percent) 2.00% 1.24% 0.92%
Maximum      
Weighted average of the assumptions used to compute employee stock based compensation      
Weighted-average expected volatility (as a percent) 81.90% 73.90% 86.80%
Expected term (in years) 9 years 9 months 7 days   10 years
Risk-free interest rate (as a percent) 2.38% 2.00% 2.45%