Stockholders' Equity - Share-Based Compensation Expense (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2018	Jan. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share-based compensation expense	$ 94	$ 81	$ 191	$ 170
Software and Software Development Costs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Capitalized computer software, gross			2	4
Cost of revenue
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share-based compensation expense	13	2	16	4
Selling and marketing
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share-based compensation expense	25	22	50	47
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share-based compensation expense	30	29	69	65
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share-based compensation expense	$ 26	$ 28	$ 56	$ 54