Fair Value Measurements (Fair Value Measurement Of Assets And Liabilities) (Details) - Measured On Recurring Basis [Member] - USD ($) $ in Millions		Jan. 27, 2019	Jul. 29, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets at fair value		$ 83	$ 93
Total liabilities at fair value		112	114
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets at fair value		6	11
Total liabilities at fair value		108	111
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets at fair value		7	5
Total liabilities at fair value		4	3
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets at fair value		70	77
Foreign Exchange Forward Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets at fair value	[1]	3	4
Derivatives liabilities at fair value	[1]	3	2
Foreign Exchange Forward Contracts [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets at fair value	[1]	3	4
Derivatives liabilities at fair value	[1]	3	2
Commodity Derivative Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets at fair value	[2]	4	5
Derivatives liabilities at fair value	[2]	4	4
Commodity Derivative Contracts [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets at fair value	[2]	2	5
Derivatives liabilities at fair value	[2]	3	3
Commodity Derivative Contracts [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets at fair value	[2]	2	0
Derivatives liabilities at fair value	[2]	1	1
Deferred Compensation Derivative Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets at fair value	[3]	2	1
Deferred Compensation Derivative Contracts [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets at fair value	[3]	2	1
Deferred Compensation Investment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	[4]	4	6
Deferred Compensation Investment [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	[4]	4	6
Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	[5]	70	77
Equity Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	[5]	70	77
Deferred Compensation Obligation [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation obligation	[4]	105	108
Deferred Compensation Obligation [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation obligation	[4]	$ 105	$ 108

[1] Based on observable market transactions of spot currency rates and forward rates.

[2] Based on quoted futures exchanges and on observable prices of transactions in the marketplace.

[3] Based on LIBOR and equity index swap rates.

[4] Based on the fair value of the participants’ investments.

[5] Primarily represents investments in equity securities that are not readily marketable and are accounted for under the fair value option. The investments were funded by Acre. See Note 12 for additional information. Fair value is based on analyzing recent transactions and transactions of comparable companies, and the discounted cash flow method. In addition, allocation methods, including the option pricing method, are used in distributing fair value among various equity holders according to rights and preferences.