Goodwill and Acquired Intangible Assets - Schedule of Acquired Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Jul. 31, 2019	Jul. 31, 2018	Jul. 31, 2017
Finite-lived Intangible Assets [Roll Forward]
Intangible Assets, Gross, beginning balance	$ 0
Additions	9,616
Intangible Assets, Gross, ending balance	9,616	$ 0
Accumulated Amortization, beginning balance	0
Amortization Expense	(908)	0	$ 0
Accumulated Amortization, ending balance	(908)	0
Total	$ 8,708	0
Weighted Average Useful life	3 years 6 months
Developed technology
Finite-lived Intangible Assets [Roll Forward]
Intangible Assets, Gross, beginning balance	$ 0
Additions	9,456
Intangible Assets, Gross, ending balance	9,456	0
Accumulated Amortization, beginning balance	0
Amortization Expense	(897)
Accumulated Amortization, ending balance	(897)	0
Total	$ 8,559	0
Weighted Average Useful life	3 years 6 months
Customer relationships
Finite-lived Intangible Assets [Roll Forward]
Intangible Assets, Gross, beginning balance	$ 0
Additions	160
Intangible Assets, Gross, ending balance	160	0
Accumulated Amortization, beginning balance	0
Amortization Expense	(11)
Accumulated Amortization, ending balance	(11)	0
Total	$ 149	$ 0
Weighted Average Useful life	4 years 8 months 12 days