Derivative Instruments (Derivatives Recorded At Fair Value) (Details) (USD $) In Millions, unless otherwise specified	Jan. 28, 2012	Jul. 30, 2011
Derivatives, Fair Value [Line Items]
Derivative assets	$ 239	$ 222
Derivative liabilities	48	24
Derivatives Designated As Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	233	213
Derivative liabilities	27	12
Derivatives Not Designated As Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	6	9
Derivative liabilities	21	12
Foreign Currency Derivatives [Member] | Derivatives Designated As Hedging Instrument [Member] | Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	11	67
Foreign Currency Derivatives [Member] | Derivatives Designated As Hedging Instrument [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liabilities	27	12
Foreign Currency Derivatives [Member] | Derivatives Not Designated As Hedging Instruments [Member] | Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	5	7
Foreign Currency Derivatives [Member] | Derivatives Not Designated As Hedging Instruments [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liabilities	21	12
Interest Rate Derivatives [Member] | Derivatives Designated As Hedging Instrument [Member] | Other Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	222	146
Equity Derivatives [Member] | Derivatives Not Designated As Hedging Instruments [Member] | Other Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	$ 1	$ 2