Stock-Based Compensation - Summary of Stock Option Activity Under Equity Incentive Plans and Related Information (Details) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jul. 31, 2018	Jan. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Shares Subject to Options Outstanding, Beginning balance	10,843,120
Shares Subject to Options Outstanding, Options granted	697,686
Shares Subject to Options Outstanding, Options exercised	(1,446,438)
Shares Subject to Options Outstanding, Options forfeited/cancelled	(408,689)
Shares Subject to Options Outstanding, Ending balance	9,685,679	10,843,120
Shares Subject to Options Outstanding, Vested and expected to vest	9,601,241
Shares Subject to Options Outstanding, Exercisable	7,817,955
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted Average Exercise Price, Beginning Balance	$ 8.32
Weighted Average Exercise Price, Options granted	20.84
Weighted Average Exercise Price, Options exercised	8.87
Weighted Average Exercise Price, Options forfeited/cancelled	13.93
Weighted Average Exercise Price, Ending Balance	8.90	$ 8.32
Weighted Average Exercise Price, Vested and expected to vest	8.82
Weighted Average Exercise Price, Exercisable	$ 6.73
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted Average Remaining Contractual Life (Years)	5 years 5 months 8 days	5 years 8 months 26 days
Weighted Average Remaining Contractual Life (Years), Vested and expected to vest	5 years 4 months 28 days
Weighted Average Remaining Contractual Life (Years), Exercisable	4 years 7 months 28 days
Aggregate Intrinsic Value, Balance	$ 146,041	$ 150,922
Aggregate Intrinsic Value, Vested and expected to vest	145,527
Aggregate Intrinsic Value, Exercisable	$ 134,679