XML 55 R45.htm IDEA: XBRL DOCUMENT v3.8.0.1
Share-based compensation - 2014 Plan Share Options (Details) - USD ($)
$ / shares in Units, $ in Millions
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Weighted-average assumptions used to estimate fair value of share options granted during year    
Expected volatility (as a percent) 75.00% 75.00%
Expected terms (in years) 10 years 10 years
Risk free interest rate, minimum (as a percent)   2.53%
Risk free interest rate, maximum (as a percent)   2.70%
Expected dividend (as a percent) 0.00% 0.00%
2014 Plan    
Options    
Outstanding at beginning of year (in shares) 72,818  
Outstanding at end of year (in shares) 63,818  
2014 Plan | Share options    
Options    
Outstanding at beginning of year (in shares) 2,456,433  
Granted (in shares) 614,637  
Forfeited (in shares) (50,102)  
Expired (in shares) (8,921)  
Exercised (in shares) (135,572)  
Outstanding at end of year (in shares) 2,876,475  
Fully vested and exercisable at end of year (in shares) 937,773  
Outstanding and expected to vest at end of year (in shares) 1,938,702  
Weighted average exercise price    
Outstanding at beginning of year (in dollars per share) $ 10.06  
Granted (in dollars per share) 20.11  
Forfeited (in dollars per share) 10.13  
Expired (in dollars per share) 14.00  
Exercised (in dollars per share) 11.27  
Outstanding at end of year (in dollars per share) 12.14  
Fully vested and exercisable at end of year (in dollars per share) 11.58  
Outstanding and expected to vest at end of year (in dollars per share) $ 12.41  
Total weighted average grant date fair value of options issued during the period (in $ million) $ 7.3  
Proceeds from option sales $ 1.6  
Weighted-average assumptions used to estimate fair value of share options granted during year    
Risk free interest rate, minimum (as a percent) 2.77%  
Risk free interest rate, maximum (as a percent) 2.99%  
2014 Plan | Non-executive directors    
Weighted average exercise price    
Vesting percentage per year 25.00%  
Vesting period 4 years  
2014 Plan | Directors and Officers | Share options    
Options    
Granted (in shares) 221,961  
Weighted average exercise price    
Total weighted average grant date fair value of options issued during the period (in $ million) $ 2.5  
2014 Plan | One year from grant date    
Weighted average exercise price    
Vesting period 1 year  
2014 Plan | Years two, three and four    
Weighted average exercise price    
Vesting period 1 year