Supplemental Financial Statement Data (Other Expenses / (Income)) (Details) - USD ($) $ in Millions	3 Months Ended
	Oct. 29, 2017	Oct. 30, 2016
Disclosure Text Block Supplement [Abstract]
Amortization of Intangible Assets	$ 4	$ 5
Net Periodic Defined Benefits Expense (Income), Excluding Service Cost Component	(42)	5
Gain (Loss) on Investments	8	0
Other Nonoperating Expense	1	1
Other expenses / (income)	$ (29)	$ 11