Share Repurchases (Details) - USD ($) shares in Millions, $ in Millions	6 Months Ended
	Jan. 29, 2017	Jan. 31, 2016
Statement [Line Items]
Shares repurchased, value	$ 234	$ 86
June 2011 Program [Member]
Statement [Line Items]
Authorized amount for shares repurchase	1,000
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 250
Treasury Stock [Member]
Statement [Line Items]
Treasury stock purchased, shares	4	2
Shares repurchased, value	$ 234	$ 86
Treasury Stock [Member] | June 2011 Program [Member]
Statement [Line Items]
Shares repurchased, value	$ 200