Equity Incentive Plans - Schedule of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands			3 Months Ended		9 Months Ended
	Oct. 31, 2017	Jan. 31, 2017	Oct. 31, 2017	Oct. 31, 2016	Oct. 31, 2017	Oct. 31, 2016
Shares Available for Grant
Balance - beginning of period (in shares)					678,260
Authorized (in shares)					3,000,000
Options granted (in shares)					(3,596,525)
Early exercised shares repurchased (in shares)					21,721
Options forfeited and expired (in shares)					669,623
Balance - end of period (in shares)	718,529	678,260	718,529		718,529
Shares
Balance - beginning of period (in shares)					11,090,597
Options granted (in shares)					3,596,525
Options exercised (in shares)					(1,242,172)
Options forfeited and expired (in shares)					(669,623)
Balance - end of period (in shares)	12,775,327	11,090,597	12,775,327		12,775,327
Options vested and exercisable (in shares)	5,011,187	4,344,092	5,011,187		5,011,187
Weighted- Average Exercise Price Per Share
Balance - beginning of period (in dollars per share)					$ 6.47
Options granted (in dollars per share)					10.57
Options exercised (in dollars per share)					7.54
Options forfeited and expired (in dollars per share)					7.49
Balance - end of period (in dollars per share)	$ 7.56	$ 6.47	$ 7.56		7.56
Options vested and exercisable (in dollars per share)	$ 6.29	$ 6.21	$ 6.29		$ 6.29
Weighted- Average Remaining Contractual Term (In Years)
Balance	8 years	8 years 2 months 12 days
Options vested and exercisable	6 years 9 months 18 days	7 years 3 months 18 days
Aggregate Intrinsic Value
Balance	$ 292,772	$ 21,717	$ 292,772		$ 292,772
Options vested and exercisable	$ 121,224	$ 9,875	$ 121,224		$ 121,224
Restricted Stock Units (RSUs)
Shares Available for Grant
RSUs granted (in shares)			(29,550)	0	(54,550)	0