v3.20.1
Stock-based compensation - Stock Option Activity (Details) - USD ($)
$ / shares in Units, shares in Thousands, $ in Thousands
12 Months Ended
Jan. 31, 2020
Jan. 31, 2019
Number of options    
Opening balance (shares) 2,444  
Granted (shares) 108  
Number of shares exercised (shares) (465)  
Forfeited (shares) (47)  
Ending balance (shares) 2,040 2,444
Vested and expected to vest as of year end (shares) 2,040  
Exercisable as of year end (shares) 1,426  
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) 59.63  
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 (dollars per share) 24.58  
Forfeited (usd per share) 31.09  
Ending balance (usd per share) 30.35 $ 27.37
Vested and expected to vest as of year end, weighted average exercise price (usd per share) 30.35  
Exercisable as of year end (usd per share) $ 23.53  
Weighted- average contractual term (in years) 5 years 10 months 24 days 6 years 8 months 26 days
Vested and expected to vest as of year end, weighted- average contractual term (in years) 5 years 10 months 24 days  
Exercisable as of year end, weighted-average contractual term (in years) 5 years 3 months 18 days  
Aggregate intrinsic value $ 74,009 $ 85,971
Vested and expected to vest as of year end, aggregate intrinsic value 74,009  
Exercisable as of year end, aggregate intrinsic value $ 60,744