Quarterly report pursuant to Section 13 or 15(d)

Stock-Based Compensation - Weighted-Average Assumptions Used to Estimate Fair Value of Options Granted (Details)

v3.7.0.1
Stock-Based Compensation - Weighted-Average Assumptions Used to Estimate Fair Value of Options Granted (Details) - $ / shares
3 Months Ended 6 Months Ended
Jun. 30, 2017
Jun. 30, 2016
Jun. 30, 2017
Jun. 30, 2016
Stock options        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Volatility 76.91%   74.31%  
Risk free interest rate 1.87%   1.99%  
Dividend yield 0.00%   0.00%  
Term (years) 5 years 10 months 24 days   5 years 11 months 23 days  
Weighted-average fair value of options granted during the period (usd per share) $ 2.75   $ 1.88  
Non-Employee        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Volatility 76.39% 74.61% 76.90% 75.26%
Risk free interest rate 2.19% 1.27% 2.21% 1.42%
Dividend yield 0.00% 0.00% 0.00% 0.00%
Term (years) 6 years 10 months 21 days 7 years 10 months 21 days 7 years 7 days 8 years 7 days