Comprehensive Income (Loss) - AOCI components (Details) - USD ($) $ in Millions	12 Months Ended
	Jul. 25, 2020	Jul. 27, 2019	Jul. 28, 2018
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of period	$ 33,571	$ 43,204	$ 66,137
Other comprehensive income (loss) before reclassifications	376	293	(681)
(Gains) losses reclassified out of AOCI	(35)	12	(348)
Tax benefit (expense)	(68)	(80)	89
Other comprehensive income (loss)		225	(940)
Balance, end of period	37,920	33,571	43,204
Net Unrealized Gains (Losses) on Available-for-Sale Investments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of period	0	(310)	373
Other comprehensive income (loss) before reclassifications	420	560	(543)
(Gains) losses reclassified out of AOCI	(42)	13	(287)
Tax benefit (expense)	(63)	(95)	93
Other comprehensive income (loss)		478	(737)
Balance, end of period	315	0	(310)
Net Unrealized Gains (Losses) Cash Flow Hedging Instruments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of period		(11)	32
Other comprehensive income (loss) before reclassifications		0	21
(Gains) losses reclassified out of AOCI		(3)	(68)
Tax benefit (expense)		0	4
Other comprehensive income (loss)		(3)	(43)
Balance, end of period			(11)
Net Unrealized Gains (Losses) Cash Flow Hedging Instruments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of period	(14)
Other comprehensive income (loss) before reclassifications	7
(Gains) losses reclassified out of AOCI	1
Tax benefit (expense)	0
Balance, end of period	(6)	(14)
Cumulative Translation Adjustment and Actuarial Gains and Losses
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of period	(778)	(528)	(359)
Other comprehensive income (loss) before reclassifications	(51)	(267)	(159)
(Gains) losses reclassified out of AOCI	6	2	7
Tax benefit (expense)	(5)	15	(8)
Other comprehensive income (loss)		(250)	(160)
Balance, end of period	(828)	(778)	(528)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of period	(792)	(849)	46
Balance, end of period	$ (519)	(792)	(849)
Cumulative Effect, Period of Adoption, Adjustment
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of period		3,729	9
Balance, end of period			3,729
Cumulative Effect, Period of Adoption, Adjustment | Net Unrealized Gains (Losses) on Available-for-Sale Investments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of period		(168)	54
Balance, end of period			(168)
Cumulative Effect, Period of Adoption, Adjustment | Net Unrealized Gains (Losses) Cash Flow Hedging Instruments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of period		0	0
Balance, end of period			0
Cumulative Effect, Period of Adoption, Adjustment | Cumulative Translation Adjustment and Actuarial Gains and Losses
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of period		0	(9)
Balance, end of period			0
Cumulative Effect, Period of Adoption, Adjustment | Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of period		$ (168)	45
Balance, end of period			$ (168)