Fair Value (Assets and Liabilities Measured At Fair Value On Recurring Basis) (Details) - USD ($)	Oct. 28, 2017	Jul. 29, 2017
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	$ 69,862,000,000	$ 68,824,000,000
Derivative liabilities	18,000,000	4,000,000
Level 1
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	10,884,000,000	11,274,000,000
Derivative liabilities	0	0
Level 2
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	58,978,000,000	57,550,000,000
Derivative liabilities	18,000,000	4,000,000
Level 3
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	0	0
Derivative liabilities	0	0
Cash equivalents: | Money market funds
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	9,103,000,000	9,567,000,000
Cash equivalents: | Money market funds | Level 1
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	9,103,000,000	9,567,000,000
Cash equivalents: | Money market funds | Level 2
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	0	0
Cash equivalents: | Money market funds | Level 3
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	0	0
Cash equivalents: | U.S. government securities
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	0	139,000,000
Cash equivalents: | U.S. government securities | Level 1
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	0	0
Cash equivalents: | U.S. government securities | Level 2
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	0	139,000,000
Cash equivalents: | U.S. government securities | Level 3
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	0	0
Cash equivalents: | Commercial paper
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	115,000,000	160,000,000
Cash equivalents: | Commercial paper | Level 1
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	0	0
Cash equivalents: | Commercial paper | Level 2
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	115,000,000	160,000,000
Cash equivalents: | Commercial paper | Level 3
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	0	0
Cash equivalents: | Certificates of deposit
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	0	25,000,000
Cash equivalents: | Certificates of deposit | Level 1
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	0	0
Cash equivalents: | Certificates of deposit | Level 2
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	0	25,000,000
Cash equivalents: | Certificates of deposit | Level 3
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	0	0
Available-for-sale investments: | U.S. government securities
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	20,471,000,000	19,823,000,000
Available-for-sale investments: | U.S. government securities | Level 1
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	0	0
Available-for-sale investments: | U.S. government securities | Level 2
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	20,471,000,000	19,823,000,000
Available-for-sale investments: | U.S. government securities | Level 3
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	0	0
Available-for-sale investments: | U.S. government agency securities
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	1,917,000,000	2,052,000,000
Available-for-sale investments: | U.S. government agency securities | Level 1
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	0	0
Available-for-sale investments: | U.S. government agency securities | Level 2
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	1,917,000,000	2,052,000,000
Available-for-sale investments: | U.S. government agency securities | Level 3
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	0	0
Available-for-sale investments: | Non-U.S. government and agency securities
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	357,000,000	388,000,000
Available-for-sale investments: | Non-U.S. government and agency securities | Level 1
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	0	0
Available-for-sale investments: | Non-U.S. government and agency securities | Level 2
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	357,000,000	388,000,000
Available-for-sale investments: | Non-U.S. government and agency securities | Level 3
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	0	0
Available-for-sale investments: | Corporate debt securities
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	32,030,000,000	31,735,000,000
Available-for-sale investments: | Corporate debt securities | Level 1
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	0	0
Available-for-sale investments: | Corporate debt securities | Level 2
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	32,030,000,000	31,735,000,000
Available-for-sale investments: | Corporate debt securities | Level 3
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	0	0
Available-for-sale investments: | U.S. agency mortgage-backed securities
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	2,074,000,000	2,023,000,000
Available-for-sale investments: | U.S. agency mortgage-backed securities | Level 1
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	0	0
Available-for-sale investments: | U.S. agency mortgage-backed securities | Level 2
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	2,074,000,000	2,023,000,000
Available-for-sale investments: | U.S. agency mortgage-backed securities | Level 3
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	0	0
Available-for-sale investments: | Commercial paper
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	1,775,000,000	996,000,000
Available-for-sale investments: | Commercial paper | Level 1
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	0	0
Available-for-sale investments: | Commercial paper | Level 2
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	1,775,000,000	996,000,000
Available-for-sale investments: | Commercial paper | Level 3
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	0	0
Available-for-sale investments: | Certificates of deposit
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	140,000,000	60,000,000
Available-for-sale investments: | Certificates of deposit | Level 1
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	0	0
Available-for-sale investments: | Certificates of deposit | Level 2
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	140,000,000	60,000,000
Available-for-sale investments: | Certificates of deposit | Level 3
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	0	0
Available-for-sale investments: | Publicly traded equity securities
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	1,781,000,000	1,707,000,000
Available-for-sale investments: | Publicly traded equity securities | Level 1
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	1,781,000,000	1,707,000,000
Available-for-sale investments: | Publicly traded equity securities | Level 2
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	0	0
Available-for-sale investments: | Publicly traded equity securities | Level 3
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	0	0
Derivative assets
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	99,000,000	149,000,000
Derivative assets | Level 1
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	0	0
Derivative assets | Level 2
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	99,000,000	149,000,000
Derivative assets | Level 3
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	0	0
Derivative liabilities
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Derivative liabilities	18,000,000	4,000,000
Derivative liabilities | Level 1
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Derivative liabilities	0	0
Derivative liabilities | Level 2
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Derivative liabilities	18,000,000	4,000,000
Derivative liabilities | Level 3
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Derivative liabilities	$ 0	$ 0