Annual report pursuant to Section 13 and 15(d)

Stock-based compensation - Stock option grants (Details)

v3.3.1.900
Stock-based compensation - Stock option grants (Details) - Employee Stock Option [Member] - $ / shares
1 Months Ended 12 Months Ended
Nov. 30, 2014
Aug. 31, 2014
Jun. 30, 2014
Feb. 28, 2014
Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Number of shares 115,000 275,000 690,000 200,000 0
Exercise price (in dollars per share) $ 4.90 $ 5.00 $ 4.85 $ 6.00 $ 0.00