Derivative Instruments (Effect Of Derivative Instruments Designated As Fair Value Hedges And Underlying Hedged Items On Consolidated Statements Of Operations Summary) (Details) (Derivatives Designated As Fair Value Hedging Instruments [Member], USD $) In Millions, unless otherwise specified	3 Months Ended
	Oct. 27, 2012	Oct. 29, 2011
Hedge Underlying Gain Loss [Line Items]
Gains (losses) on derivative instruments	$ (21)	$ 35
Gains (losses) related to hedged items	21	(36)
Equity Contract [Member] | Other Income (loss), net [Member]
Hedge Underlying Gain Loss [Line Items]
Gains (losses) on derivative instruments	(3)	0
Gains (losses) related to hedged items	3	0
Interest Rate Contract [Member] | Interest Expense [Member]
Hedge Underlying Gain Loss [Line Items]
Gains (losses) on derivative instruments	(18)	35
Gains (losses) related to hedged items	$ 18	$ (36)