XML 79 R67.htm IDEA: XBRL DOCUMENT v3.8.0.1
Stock award plan - Stock Option Activity (Details) - Stock option - USD ($)
$ / shares in Units, $ in Thousands
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Number of options      
Outstanding at the beginning of the period (in shares) 5,854,316 4,826,477 3,432,972
Granted (in shares) 1,913,873 1,500,645 2,201,800
Exercised (in shares) (202,085) (89,216) (656,248)
Forfeited (in shares) (1,117,462) (383,590) (152,047)
Outstanding at the end of the period (in shares) 6,448,642 5,854,316 4,826,477
Vested or expected to vest at the end of the period (in shares) 2,522,747    
Exercisable at the end of the period (in shares) 3,778,544    
Weighted- average exercise price      
Outstanding at the beginning of the period (in dollars per share) $ 34.71 $ 37.20 $ 25.00
Granted (in dollars per share) 12.34 27.90 50.81
Exercised (in dollars per share) 10.80 10.85 13.27
Forfeited (in dollars per share) 33.65 47.42 49.58
Outstanding at the end of the period (in dollars per share) 29.00 $ 34.71 $ 37.20
Vested or expected to vest at the end of the period (in dollars per share) 23.29    
Exercisable at the end of the period (in dollars per share) $ 33.19    
Weighted- average remaining contractual term      
Outstanding at the end of the period 7 years 3 months 11 days    
Vested or expected to vest at the end of the period 8 years 4 months 21 days    
Exercisable at the end of the period 6 years 5 months 23 days    
Aggregate intrinsic value      
Outstanding at the end of the period (in dollars) $ 13,435    
Vested or expected to vest at the end of the period (in dollars) 6,822    
Exercisable at the end of the period (in dollars) $ 6,167