Quarterly report pursuant to Section 13 or 15(d)

Stock-based Compensation - Options (Details)

v3.8.0.1
Stock-based Compensation - Options (Details)
 3 Months Ended
Mar. 31, 2018
USD ($)
item
$ / shares
shares
Mar. 31, 2017
USD ($)
Stock Based Compensation    
Share-based compensation | $ $ 1,540,000 $ 955,000
Additional disclosures    
Shares of common stock available for grant | shares 10,544,883  
Employee stock option    
Stock Based Compensation    
Number of homogenous groups for purposes of determining fair values of options | item 3  
Contractual term of the option 10 years  
Weighted-average assumptions relating to options granted    
Risk-free interest rate (as a percent) 2.70% 2.30%
Expected term (in years) 6 years 8 months 12 days 6 years 9 months 18 days
Dividend yield (as a percent) 0.00% 0.00%
Expected volatility (as a percent) 64.60% 62.90%
Additional disclosures    
Options granted (in shares) | shares 3,396,975  
Grant-date weighted-average fair value (in dollars per share) | $ / shares $ 2.79  
Total unrecognized compensation costs | $ $ 14,200,000  
Options exercised during the period (in shares) | shares 652,891  
Employee stock option | Consultant    
Stock Based Compensation    
Contractual term of the option 10 years  
Employee stock option | Recipient of performance shares    
Stock Based Compensation    
Share-based compensation | $ $ 402,000  
Additional disclosures    
Options granted (in shares) | shares 2,672,500  
Grant date fair value of performance stock options awards | $ $ 5,700,000  
Total unrecognized compensation costs | $ $ 4,200,000  
Employee stock option | Recipient of performance shares | Vesting upon achievement of corporate performance-based milestones    
Additional disclosures    
Options granted (in shares) | shares 1,160,000