CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY Statement - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit
Stockholders' equity, beginning balance (in shares) at Jul. 31, 2017		154,636,520
Stockholders' equity, beginning balance at Jul. 31, 2017	$ 217,063	$ 4	$ 948,134	$ (106)	$ (730,969)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock through employee equity incentive plans, net of repurchases (in shares)		3,989,701
Issuance of common stock through employee equity incentive plans, net of repurchases	7,968		7,968
Issuance of common stock from ESPP purchase (in shares)		1,261,104
Issuance of common stock from ESPP purchase	17,402		17,402
Stock-based compensation	35,515		35,515
Vesting of early exercised stock options	249		249
Other comprehensive loss	(130)			(130)
Net loss	(61,487)				(61,487)
Stockholders' equity, ending balance (in shares) at Oct. 31, 2017		159,887,325
Stockholders' equity, ending balance at Oct. 31, 2017	216,580	$ 4	1,009,268	(236)	(792,456)
Stockholders' equity, beginning balance (in shares) at Jul. 31, 2017		154,636,520
Stockholders' equity, beginning balance at Jul. 31, 2017	217,063	$ 4	948,134	(106)	(730,969)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(209,792)
Stockholders' equity, ending balance (in shares) at Apr. 30, 2018		170,282,321
Stockholders' equity, ending balance at Apr. 30, 2018	354,581	$ 4	1,296,575	(1,237)	(940,761)
Stockholders' equity, beginning balance (in shares) at Oct. 31, 2017		159,887,325
Stockholders' equity, beginning balance at Oct. 31, 2017	216,580	$ 4	1,009,268	(236)	(792,456)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock through employee equity incentive plans, net of repurchases (in shares)		4,178,590
Issuance of common stock through employee equity incentive plans, net of repurchases	11,419		11,419
Stock-based compensation	42,011		42,011
Equity component of the convertible senior notes, net	148,598		148,598
Sale of warrants related to the convertible senior notes	87,975		87,975
Cost of the bond hedges related to the convertible senior notes	(143,175)		(143,175)
Vesting of early exercised stock options	186		186
Other comprehensive loss	(484)			(484)
Net loss	(62,631)				(62,631)
Stockholders' equity, ending balance (in shares) at Jan. 31, 2018		164,065,915
Stockholders' equity, ending balance at Jan. 31, 2018	300,479	$ 4	1,156,282	(720)	(855,087)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock through employee equity incentive plans, net of repurchases (in shares)		3,748,870
Issuance of common stock through employee equity incentive plans, net of repurchases	9,825		9,825
Issuance of common stock from ESPP purchase (in shares)		1,156,746
Issuance of common stock from ESPP purchase	21,607		21,607
Issuance of common stock in connection with a business combination (in shares)		1,310,790
Issuance of common stock in connection with a business combination	63,780		63,780
Stock-based compensation	44,946		44,946
Vesting of early exercised stock options	135		135
Other comprehensive loss	(517)			(517)
Net loss	(85,674)				(85,674)
Stockholders' equity, ending balance (in shares) at Apr. 30, 2018		170,282,321
Stockholders' equity, ending balance at Apr. 30, 2018	$ 354,581	$ 4	1,296,575	(1,237)	(940,761)
Stockholders' equity, beginning balance (in shares) at Jul. 31, 2018	172,858,082	172,858,082
Stockholders' equity, beginning balance at Jul. 31, 2018	$ 326,779	$ 4	1,355,907	(1,002)	(1,028,130)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock through employee equity incentive plans, net of repurchases (in shares)		2,629,079
Issuance of common stock through employee equity incentive plans, net of repurchases	3,680		3,680
Issuance of common stock from ESPP purchase (in shares)		1,127,728
Issuance of common stock from ESPP purchase	26,318		26,318
Issuance of common stock in connection with a business combination (in shares)		2,451,322
Issuance of common stock in connection with a business combination	102,978		102,978
Stock-based compensation	65,925		65,925
Vesting of early exercised stock options	70		70
Other comprehensive loss	(166)			(166)
Net loss	(94,265)				(94,265)
Stockholders' equity, ending balance (in shares) at Oct. 31, 2018		179,066,211
Stockholders' equity, ending balance at Oct. 31, 2018	$ 431,319	$ 4	1,554,878	(1,168)	(1,122,395)
Stockholders' equity, beginning balance (in shares) at Jul. 31, 2018	172,858,082	172,858,082
Stockholders' equity, beginning balance at Jul. 31, 2018	$ 326,779	$ 4	1,355,907	(1,002)	(1,028,130)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	$ (426,841)
Stockholders' equity, ending balance (in shares) at Apr. 30, 2019	185,900,407	185,900,407
Stockholders' equity, ending balance at Apr. 30, 2019	$ 305,446	$ 5	1,760,083	329	(1,454,971)
Stockholders' equity, beginning balance (in shares) at Oct. 31, 2018		179,066,211
Stockholders' equity, beginning balance at Oct. 31, 2018	431,319	$ 4	1,554,878	(1,168)	(1,122,395)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock through employee equity incentive plans, net of repurchases (in shares)		2,967,649
Issuance of common stock through employee equity incentive plans, net of repurchases	3,341		3,341
Stock-based compensation	72,565		72,565
Vesting of early exercised stock options	50		50
Other comprehensive loss	1,019			1,019
Net loss	(122,763)				(122,763)
Stockholders' equity, ending balance (in shares) at Jan. 31, 2019		182,033,860
Stockholders' equity, ending balance at Jan. 31, 2019	385,531	$ 4	1,630,834	(149)	(1,245,158)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock through employee equity incentive plans, net of repurchases (in shares)		2,980,448
Issuance of common stock through employee equity incentive plans, net of repurchases	3,154		3,154
Issuance of common stock from ESPP purchase (in shares)		880,354
Issuance of common stock from ESPP purchase	30,900	$ 1	30,899
Issuance of common stock in connection with a business combination (in shares)		5,745
Issuance of common stock in connection with a business combination	327		327
Stock-based compensation	94,832		94,832
Vesting of early exercised stock options	37		37
Other comprehensive loss	478			478
Net loss	$ (209,813)				(209,813)
Stockholders' equity, ending balance (in shares) at Apr. 30, 2019	185,900,407	185,900,407
Stockholders' equity, ending balance at Apr. 30, 2019	$ 305,446	$ 5	$ 1,760,083	$ 329	$ (1,454,971)