Stock-based Compensation (Summary of Stock-based Compensation Expense) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jan. 31, 2021	Jan. 26, 2020	Jan. 31, 2021	Jan. 26, 2020
Stock-based Compensation
Total pre-tax stock-based compensation expense	$ 18	$ 18	$ 34	$ 31
Tax-related benefits	$ 3	3	$ 6	6
Discontinued Operations, Held-for-sale or Disposed of by Sale [Member]
Stock-based Compensation
Total pre-tax stock-based compensation expense		1		2
Tax-related benefits		$ 0		$ 0

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
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
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