Investments (Realized Net Gains (Losses) Related to Available-for-Sale Investments) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jan. 27, 2018	Jan. 28, 2017	Jan. 27, 2018	Jan. 28, 2017
Schedule of Investments [Line Items]
Total	$ 58	$ (30)	$ 91	$ (15)
Net gains (losses) on investments in publicly traded equity securities
Schedule of Investments [Line Items]
Total	154	4	183	9
Net gains (losses) on investments in fixed income securities
Schedule of Investments [Line Items]
Total	$ (96)	$ (34)	$ (92)	$ (24)

This item represents the difference between the gross realized gains and losses realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities. Additionally, this item would include any losses recognized for other than temporary impairments (OTTI) of the subject investments in debt and equity securities.

Reference 1: 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=82897076&loc=d3e27357-111563

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