Property and Equipment - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Jul. 31, 2018	Jul. 31, 2017	Jul. 31, 2016
Property, Plant and Equipment [Line Items]
Capital in progress	$ 48	$ 71
Capitalized software costs	86	128	$ 103
Capitalized labor costs	45	99	$ 80
Land and Buildings
Property, Plant and Equipment [Line Items]
Capital in progress	$ 29	$ 30