v3.19.1
Stock-based compensation (Stock option activity) (Details) - USD ($)
$ / shares in Units, shares in Thousands, $ in Thousands
3 Months Ended 12 Months Ended
Apr. 30, 2019
Jan. 31, 2019
Number of options (shares)    
Opening balance (shares) 2,444  
Granted (shares) 108  
Exercised (shares) (178)  
Forfeited (shares) (18)  
Ending balance (shares) 2,356 2,444
Range of exercise prices (usd per share)    
Beginning balance, minimum (usd per share) $ 0.10  
Beginning balance, maximum (usd per share) 82.39  
Granted, minimum (usd per share) 63.64  
Granted, maximum (usd per share) 73.61  
Exercised, minimum (usd per share) 0.10  
Exercised, maximum (usd per share) 44.53  
Forfeited, minimum (usd per share) 24.36  
Forfeited, maximum (usd per share) 44.53  
Ending balance, minimum (usd per share) 0.10 $ 0.10
Ending balance, maximum (usd per share) 82.39 82.39
Weighted- average exercise price (usd per share)    
Opening balance (usd per share) 27.37  
Granted (usd per share) 73.27  
Exercised (usd per share) 24.49  
Forfeited (usd per share) 30.92  
Ending balance (usd per share) $ 29.66 $ 27.37
Weighted- average contractual term (in years) 6 years 7 months 13 days 6 years 8 months 26 days
Aggregate intrinsic value $ 90,701 $ 85,971
Vested and expected to vest as of year end (in shares) 2,356  
Vested and expected to vest as of year end, weighted average exercise price (usd per share) $ 29.66  
Vested and expected to vest as of year end, weighted average contractual term (in years) 6 years 7 months 13 days  
Vested and expected to vest as of year end, aggregate intrinsic value (usd per share) $ 90,701  
Exercisable as of year end (in shares) 1,503  
Exercisable as of year end, weighted-average exercise price (usd per share) $ 21.82  
Exercisable as of year end, weighted-average contractual term (in years) 5 years 10 months 27 days  
Exercisable as of year end, aggregate intrinsic value $ 69,042