Share Repurchases (Narrative) (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Oct. 29, 2017	Oct. 30, 2016
Statement [Line Items]
Shares repurchased, value	$ 86	$ 112
March 2017 Program [Member]
Statement [Line Items]
Authorized amount for shares repurchase	1,500
Shares repurchased, value	75
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 1,296
Treasury Stock [Member]
Statement [Line Items]
Treasury stock purchased, shares	2	2
Shares repurchased, value	$ 86	$ 112