Equity Incentive Plans and Employee Stock Purchase Plan - Schedule of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Apr. 30, 2018	Jan. 31, 2018
Shares
Balance - beginning of period (in shares)	12,637,435
Stock options granted (in shares)	0
Stock options exercised (in shares)	(40,723)
Repurchase of early exercised shares (in shares)	0
Stock options forfeited and expired (in shares)	(123,781)
Balance - end of period (in shares)	12,472,931	12,637,435
Vested and exercisable (in shares)	6,236,117	5,540,858
Weighted- Average Exercise Price Per Share
Balance - beginning of period (in dollars per share)	$ 7.63
Stock options granted (in dollars per share)	0.00
Stock options exercised (in dollars per share)	6.36
Stock options forfeited and expired (in dollars per share)	9.22
Balance - end of period (in dollars per share)	7.61	$ 7.63
Vested and exercisable (in dollars per share)	$ 6.46	$ 6.33
Weighted- Average Remaining Contractual Term (In Years)
Balance	7 years 5 months 9 days	7 years 8 months 19 days
Vested and exercisable	6 years 6 months 4 days	6 years 7 months 17 days
Aggregate Intrinsic Value
Balance	$ 353,927	$ 246,227
Vested and exercisable	$ 184,152	$ 115,122