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. 26, 2019	Jan. 27, 2018	Jan. 26, 2019	Jan. 27, 2018
Earnings Per Share [Abstract]
Net income	$ 2,822	$ (8,778)	$ 6,371	$ (6,384)
Weighted-average shares—basic (in shares)	4,470	4,924	4,517	4,942
Effect of dilutive potential common shares (in shares)	35	0	40	0
Weighted-average shares—diluted (in shares)	4,505	4,924	4,557	4,942
Net income (loss) per share—basic (in dollars per share)	$ 0.63	$ (1.78)	$ 1.41	$ (1.29)
Net income (loss) per share—diluted (in dollars per share)	$ 0.63	$ (1.78)	$ 1.40	$ (1.29)
Antidilutive employee share-based awards, excluded (in shares)	27		28