Annual report pursuant to Section 13 and 15(d)

Stock-based compensation - Stock option grants (Details)

v3.7.0.1
Stock-based compensation - Stock option grants (Details) - $ / shares
12 Months Ended
Sep. 19, 2016
Sep. 06, 2016
Apr. 08, 2016
Apr. 01, 2016
Dec. 31, 2016
Dec. 31, 2015
Employee Stock Option            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Number of shares 30,000 30,000 1,000,000 250,000 560,000 0
Exercise price (in dollars per share) $ 2.39 $ 2.61 $ 2.73 $ 2.83 $ 2.72  
Options Granted Upon Achievement of Certain Milestones            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Number of shares     625,000 125,000