Equity Incentive Plans and Employee Stock Purchase Plan - Schedule of Restricted Stock Unit Activity (Details) - Restricted Stock Units (RSUs)
3 Months Ended
Apr. 30, 2019
$ / shares
shares
Shares  
Unvested - beginning of period (in shares) | shares 1,988,774
RSUs granted (in shares) | shares 1,027,610
RSUs vested (in shares) | shares (126,346)
RSUs forfeited and canceled (in shares) | shares (24,629)
Unvested - end of period (in shares) | shares 2,865,409
Weighted-Average Grant Date Fair Value per RSU  
Unvested - beginning of period (in dollars per share) | $ / shares $ 54.22
RSUs granted (in dollars per share) | $ / shares 105.50
RSUs vested (in dollars per share) | $ / shares 45.42
RSUs forfeited and canceled (in dollars per share) | $ / shares 56.03
Unvested - end of period (in dollars per share) | $ / shares $ 72.98