Shareholders' Equity (Stock Repurchase Program) (Details) $ / shares in Units, shares in Millions, $ in Millions	9 Months Ended
	Apr. 30, 2016 USD ($) $ / shares shares
Stockholders' Equity Note [Abstract]
Cumulative Shares Repurchased, Beginning balance (in shares) | shares	4,443
Repurchase of Common Stock During Period (in shares) | shares	120	[1]
Cumulative Shares Repurchased, Ending balance (in shares) | shares	4,563
Cumulative Weighted-Average Price per Share, Beginning balance, dollars per share | $ / shares	$ 20.86
Repurchase of common stock under the stock repurchase program, Weighted-Average Price per Share, dollars per share | $ / shares	25.93
Cumulative Weighted-Average Price per Share, Ending balance, dollars per share | $ / shares	$ 20.99
Cumulative Amount Repurchased, Beginning balance (in dollars) | $	$ 92,679
Stock Repurchased During the Period (in dollars) | $	3,118	[1]
Cumulative Amount Repurchased, Ending balance (in dollars) | $	$ 95,797

[1] There were no stock repurchases pending settlement as of April 30, 2016. There were $36 million of stock repurchases that were pending settlement as of July 25, 2015.