Shareholders' Equity (Stock Repurchase Program) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Jul. 29, 2017	Jul. 30, 2016
Shares Repurchased
Cumulative balance, Shares repurchased, beginning of period (in shares)	4,591	4,443
Repurchase of common stock under the stock repurchase program, Shares repurchased (in shares)	118	148
Cumulative balance, Shares repurchased, end of period (in shares)	4,709	4,591
Weighted- Average Price per Share
Cumulative balance, Weighted average price per share, beginning of period (in dollars per share)	$ 21.04	$ 20.86
Cumulative weighted average price per share repurchased, Weighted average price per share (in dollars per share)	31.38	26.45
Cumulative balance, Weighted average price per share, end of period (in dollars per share)	$ 21.30	$ 21.04
Payments For Repurchase Of Equity Value [Roll Forward]
Cumulative balance, Amount repurchased, beginning of period	$ 96,597	$ 92,679
Repurchase of common stock under the stock repurchase program, Amount repurchased	3,706	3,918
Cumulative balance, Amount repurchased, end of period	100,303	96,597
Stock repurchase program
Class of Stock [Line Items]
Stock repurchases pending settlement	$ 66	$ 45