Comprehensive Income (Loss) - Reclassification out of other comprehensive income (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Jul. 25, 2020	Apr. 25, 2020	Jan. 25, 2020	Oct. 26, 2019	Jul. 27, 2019	Apr. 27, 2019	Jan. 26, 2019	Oct. 27, 2018	Jul. 25, 2020	Jul. 27, 2019	Jul. 28, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Other income (loss), net									$ 15	$ (97)	$ 165
Revenue	$ 12,154	$ 11,983	$ 12,005	$ 13,159	$ 13,428	$ 12,958	$ 12,446	$ 13,072	49,301	51,904	49,330
Cost of sales									(17,618)	(19,238)	(18,724)
Operating expenses									(18,063)	(18,447)	(18,297)
Total amounts reclassified out of AOCI									13,970	14,571	13,039
Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Total amounts reclassified out of AOCI									35	(12)	348
Reclassification out of Accumulated Other Comprehensive Income | Net Unrealized Gains (Losses) on Available-for-Sale Investments
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Other income (loss), net									42	(13)	287
Reclassification out of Accumulated Other Comprehensive Income | Net Unrealized Gains (Losses) Cash Flow Hedging Instruments
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Revenue									(1)
Cost of sales									0
Operating expenses									0
Total amounts reclassified out of AOCI									(1)
Reclassification out of Accumulated Other Comprehensive Income | Net Unrealized Gains (Losses) Cash Flow Hedging Instruments
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Revenue										2	0
Cost of sales										0	16
Operating expenses										1	52
Total amounts reclassified out of AOCI										3	68
Reclassification out of Accumulated Other Comprehensive Income | Cumulative Translation Adjustment and Actuarial Gains and Losses
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Other income (loss), net									(6)	(2)	0
Operating expenses									$ 0	$ 0	$ (7)