Stock Based Compensation - Summary of Stock Option Activity Under 2011 Stock Plan (Details) - 2011 Equity Incentive Plan - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Oct. 28, 2017	Jul. 28, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares Available for Grant, Beginning balance	2,023,424
Shares Available for Grant, Repurchased	19,479
Shares Available for Grant, Granted	(867,865)
Shares Available for Grant, Cancelled	551,641
Shares Available for Grant, Ending balance	1,726,679
Options Outstanding, Number of Options, Beginning balance	10,218,912
Options Outstanding, Number of Options, Granted	867,865
Options Outstanding, Number of Options, Exercised	(211,236)
Options Outstanding, Number of Options, Cancelled	(551,641)
Options Outstanding, Number of Options, Ending balance	10,323,900
Options Outstanding, Weighted-Average Exercise Price, Beginning balance	$ 7.12
Options Outstanding, Weighted-Average Exercise Price, Granted	23.43
Options Outstanding, Weighted-Average Exercise Price, Exercised	2.10
Options Outstanding, Weighted-Average Exercise Price, Cancelled	4.01
Options Outstanding, Weighted-Average Exercise Price, Ending balance	$ 8.76
Options Outstanding, Weighted-Average Remaining Contractual Life (in Years)	8 years 5 months 12 days	8 years 6 months 10 days
Options Outstanding, Aggregate Intrinsic Value	$ 87,531	$ 166,670