Stock-based Compensation (Summary of Stock-based Compensation Expense) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jan. 26, 2020	Jan. 27, 2019	Jan. 26, 2020	Jan. 27, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total pre-tax stock-based compensation expense	$ 18	$ 15	$ 31	$ 28
Tax-related benefits	3	3	6	5
Discontinued Operations, Held-for-sale or Disposed of by Sale [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total pre-tax stock-based compensation expense	1	2	2	3
Tax-related benefits	$ 0	$ 0	$ 0	$ 1

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5047-113901

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.F)
-URI http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(i)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

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