Investments (Gross Realized Gains And Gross Realized Losses Related To Available-For-Sale Investments) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
Apr. 28, 2012	Apr. 30, 2011	Apr. 28, 2012	Apr. 30, 2011
Investments [Abstract]
Gross realized gains	$ 118	$ 107	$ 542	$ 272
Gross realized losses	(88)	(58)	(466)	(116)
Total	$ 30	$ 49	$ 76	$ 156

This item represents the gross profit realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 21

-Subparagraph a

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 9

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27357-111563

Name:	us-gaap_AvailableForSaleSecuritiesGrossRealizedGains
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration