BALANCE SHEET COMPONENTS - Intangible Assets (Details) - USD ($) $ in Thousands			3 Months Ended								12 Months Ended
	Sep. 06, 2016	Aug. 22, 2016	Jul. 31, 2018	Apr. 30, 2018	Jan. 31, 2018	Oct. 31, 2017	Jul. 31, 2017	Apr. 30, 2017	Jan. 31, 2017	Oct. 31, 2016	Jul. 31, 2018	Jul. 31, 2017	Jul. 31, 2018	Jul. 31, 2017
Finite-lived intangible assets:
Finite-lived intangible assets, gross													$ 54,150	$ 12,130
Total intangible assets, gross													54,150	28,230
Less:
Accumulated amortization													(8,784)	(2,229)
Intangible assets, net			$ 45,366			$ 26,001	$ 26,001			$ 0	$ 26,001	$ 0	45,366	26,001
Finite-lived Intangible Assets [Roll Forward]
Intangible assets, net—beginning balance						26,001				0	26,001	0
Amortization of intangible assets			(2,424)	$ (1,669)	$ (1,356)	$ (1,106)	(608)	$ (608)	$ (608)	$ (405)	(6,555)	(2,229)
Intangible assets, net—ending balance			$ 45,366				$ 26,001				45,366	26,001
Calm Acquisition
Less:
Estimated Life (in years)		4 years 10 months
Finite-lived Intangible Assets [Roll Forward]
Intangible assets acquired											$ 25,920	$ 28,230
In-process R&D
Indefinite-lived intangible asset:
In-process R&D													0	16,100
Developed technology
Finite-lived intangible assets:
Finite-lived intangible assets, gross													47,500	7,300
Less:
Accumulated amortization													(6,956)	(1,314)
Estimated Life (in years)	5 years
Developed technology | PernixData Acquisition
Finite-lived Intangible Assets [Roll Forward]
Intangible assets acquired	$ 3,570
Customer relationships
Finite-lived intangible assets:
Finite-lived intangible assets, gross													6,650	4,830
Less:
Accumulated amortization													$ (1,828)	$ (915)
Customer relationships | PernixData Acquisition
Finite-lived Intangible Assets [Roll Forward]
Intangible assets acquired	$ 4,600