Net Income (Loss) per Share (Calculation of Basic and Diluted Net Income per Share) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jan. 27, 2018	Jan. 28, 2017	Jan. 27, 2018	Jan. 28, 2017
Earnings Per Share [Abstract]
Net income (loss)	$ (8,778)	$ 2,348	$ (6,384)	$ 4,670
Weighted-average shares—basic (in shares)	4,924	5,015	4,942	5,021
Effect of dilutive potential common shares (in shares)	0	25	0	33
Weighted-average shares—diluted (in shares)	4,924	5,040	4,942	5,054
Net income (loss) per share—basic (in dollars per share)	$ (1.78)	$ 0.47	$ (1.29)	$ 0.93
Net income (loss) per share—diluted (in dollars per share)	$ (1.78)	$ 0.47	$ (1.29)	$ 0.92