Fair Value Measurements (Fair Value Measurement Of Assets And Liabilities) (Details) - Measured On Recurring Basis [Member] - USD ($) $ in Millions		Jan. 26, 2020	Jul. 28, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets at fair value		$ 86	$ 85
Total liabilities at fair value		113	105
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets at fair value		8	6
Total liabilities at fair value		109	98
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets at fair value		2	3
Total liabilities at fair value		4	7
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets at fair value		76	76
Foreign Exchange Forward Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets at fair value	[1]	1	1
Derivatives liabilities at fair value	[1]	1	4
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]	1	1
Derivatives liabilities at fair value	[1]	1	4
Commodity Derivative Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets at fair value	[2]	8	3
Derivatives liabilities at fair value	[2]	5	6
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]	5	2
Derivatives liabilities at fair value	[2]	2	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]	0	1
Derivatives liabilities at fair value	[2]	3	3
Commodity Derivative Contracts [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets at fair value	[2]	3	0
Deferred Compensation Derivative Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets at fair value	[3]	1	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]	1	1
Deferred Compensation Investment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	[4]	3	4
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]	3	4
Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	[5]	73	76
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]	73	76
Deferred Compensation Obligation [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation obligation	[4]	107	95
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]	$ 107	$ 95

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

[2] Level 1 and 2 are based on quoted futures exchanges and on observable prices of futures and options transactions in the marketplace. Level 3 is based on unobservable inputs in which there is little or no market data, which requires management’s own assumptions within an internally developed model.

[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 14 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.