Employee Incentive Plans - Schedule of Common Stock Reserved for Future Issuance (Details)	Jul. 31, 2018 shares
Class of Stock [Line Items]
Common stock reserved for future issuance and options and unvested RSUs outstanding (in shares)	41,289,127
Stock Options And Restricted Stock Units
Class of Stock [Line Items]
Stock options and unvested RSUs outstanding (in shares)	25,789,276
Common stock, reserved for future issuance (in shares)	12,464,154
ESPP
Class of Stock [Line Items]
Common stock, reserved for future issuance (in shares)	3,035,697