Comprehensive Income (Reclassified Out of Other Comprehensive Income) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Oct. 26, 2013	Oct. 27, 2012
Available-for-sale Securities [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amount Reclassified Out of OCI, Before Tax	$ (83)	$ (27)
Available-for-sale Securities [Member] | Other income (loss), net [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amount Reclassified Out of OCI, Before Tax	(83)	(27)
Derivative [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amount Reclassified Out of OCI, Before Tax	(9)	5
Derivative [Member] | Operating Expenses [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amount Reclassified Out of OCI, Before Tax	(7)	4
Derivative [Member] | Cost Of Sales-Service [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amount Reclassified Out of OCI, Before Tax	(2)	1
Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amount Reclassified Out of OCI, Before Tax	$ (92)	$ (22)