EQUITY AWARD PLANS - Additional Information (Details)				3 Months Ended	9 Months Ended
	Aug. 01, 2018 shares	Aug. 01, 2017 shares	Sep. 30, 2016 USD ($) purchase_period shares	Apr. 30, 2019 USD ($) $ / shares shares	Apr. 30, 2019 USD ($) plan $ / shares shares	Apr. 30, 2018 USD ($)	Jul. 31, 2016 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of equity incentive plans | plan					3
Exercises in period (in shares)					2,194,303
Weighted average exercise price (in dollars per share) | $ / shares					$ 4.64
Options outstanding (in shares)				9,103,232	9,103,232
Outstanding options, weighted average exercise price (in dollars per share) | $ / shares				$ 5.22	$ 5.22
Contractual term					4 years 10 months 24 days
Options outstanding, intrinsic value | $				$ 345,700,000	$ 345,700,000
Compensation not yet recognized | $				$ 791,300,000	$ 791,300,000
Period for recognition (in years)					2 years 6 months
Proceeds from stock plans | $					$ 67,277,000	$ 68,186,000
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)					8,445,399
Granted (in dollars per share) | $ / shares					$ 47.63
Released (in dollars per share) | $ / shares					$ 28.07
Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percent of eligible compensation (up to)			15.00%
Monetary cap | $			$ 25,000
Share cap (in shares)			1,000
Offering period duration (in months)			12 months
Number of six-month purchase periods | purchase_period			2
Purchase price of common stock, percent			85.00%
ESPP stock issued during period (in shares)				2,008,082
Proceeds from stock plans | $				$ 57,200,000
Common Class A | Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for future issuance (in shares)			3,800,000
Annual increase (in shares)			3,800,000
Annual increase, percent of outstanding shares			1.00%
Number of additional shares authorized	1,728,580	1,546,365
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for future issuance (in shares)				1,402,959	1,402,959
2016 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for future issuance (in shares)				46,199,635	46,199,635
2016 Plan | Common Class A
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for future issuance (in shares)							22,400,000
Annual increase (in shares)				18,000,000	18,000,000
Annual increase, percent of outstanding shares				5.00%	5.00%
Number of additional shares authorized	8,642,904	7,731,826
Number of shares available for grant (in shares)				13,827,893	13,827,893
Market Stock Units | RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)					100,000
Granted (in dollars per share) | $ / shares					$ 25.16
Released (in dollars per share) | $ / shares					$ 80
Award vesting period					4 years 6 months
Equity instruments outstanding (in shares)				100,000	100,000