Comprehensive Income - AOCI Components (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jan. 25, 2020	Jan. 26, 2019	Jan. 25, 2020	Jan. 26, 2019
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Other comprehensive income (loss)	$ 115	$ 108	$ 92	$ (93)
Net Unrealized Gains (Losses) on Available-for-Sale Investments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance			0	(310)
Other comprehensive income (loss) before reclassifications			168	86
(Gains) losses reclassified out of AOCI			(21)	11
Tax benefit (expense)			(17)	0
Other comprehensive income (loss)				97
Effect of adoption of accounting standards		(168)		(168)
Ending balance	130	(381)	130	(381)
Net Unrealized Gains (Losses) Cash Flow Hedging Instruments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance			(14)
Other comprehensive income (loss) before reclassifications			0
(Gains) losses reclassified out of AOCI			2
Tax benefit (expense)			1
Ending balance	(11)		(11)
Net Unrealized Gains (Losses) Cash Flow Hedging Instruments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance				(11)
Other comprehensive income (loss) before reclassifications				(9)
(Gains) losses reclassified out of AOCI				(1)
Tax benefit (expense)				2
Other comprehensive income (loss)				(8)
Effect of adoption of accounting standards		0		0
Ending balance		(19)		(19)
Cumulative Translation Adjustment and Actuarial Gains (Losses)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance			(778)	(528)
Other comprehensive income (loss) before reclassifications			(42)	(184)
(Gains) losses reclassified out of AOCI			2	3
Tax benefit (expense)			(1)	(1)
Other comprehensive income (loss)				(182)
Effect of adoption of accounting standards		0		0
Ending balance	(819)	(710)	(819)	(710)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(815)	(1,218)	(792)	(849)
Other comprehensive income (loss) before reclassifications			126	(107)
(Gains) losses reclassified out of AOCI			(17)	13
Tax benefit (expense)			(17)	1
Other comprehensive income (loss)	115	108	92	(93)
Effect of adoption of accounting standards	(168)	(168)	(168)	(168)
Ending balance	$ (700)	$ (1,110)	$ (700)	$ (1,110)