Comprehensive Income (Reclassification out of other comprehensive income) (Details) - USD ($) $ in Millions	12 Months Ended
	Jul. 29, 2017	Jul. 30, 2016	Jul. 25, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Total amounts reclassified out of AOCI	$ (182)	$ (15)	$ 1
Cumulative translation adjustment and actuarial gains and losses
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Cumulative translation adjustment and actuarial gains and losses	(16)	6	(2)
Reclassification out of Accumulated Other Comprehensive Income | Net unrealized gains and losses on available-for-sale investments
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Other income (loss), net	(87)	(1)	157
Reclassification out of Accumulated Other Comprehensive Income | Net unrealized gains and losses on cash flow hedging instruments | Derivatives designated as cash flow hedging instruments:
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Operating expenses	(59)	(15)	(121)
Cost of sales—service	(20)	(5)	(33)
Net unrealized gains and losses on cash flow hedging instruments	$ (79)	$ (20)	$ (154)