Property and Equipment - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2015
Property, Plant and Equipment [Line Items]
Capital in progress	$ 71	$ 256
Capitalized software costs	128	103	$ 116
Capitalized labor costs	99	80	$ 89
Land and Buildings
Property, Plant and Equipment [Line Items]
Capital in progress	$ 30	$ 172