Fair Value (Assets and Liabilities Measured at Fair Value on Recurring Basis) (Details) - USD ($) $ in Millions	Jan. 27, 2018	Jul. 29, 2017
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	$ 71,727	$ 68,824
Derivative liabilities	76	4
Level 1
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	17,157	11,274
Derivative liabilities	0	0
Level 2
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	54,570	57,550
Derivative liabilities	76	4
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	15,537	9,567
Cash equivalents: | Money market funds | Level 1
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	15,537	9,567
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
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
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	41	160
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	41	160
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
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
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	17,366	19,823
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	17,366	19,823
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	1,712	2,052
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	1,712	2,052
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	339	388
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	339	388
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	31,355	31,735
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	31,355	31,735
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	2,057	2,023
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	2,057	2,023
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	1,414	996
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	1,414	996
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	196	60
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	196	60
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	1,620	1,707
Available-for-sale investments: | Publicly traded equity securities | Level 1
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Total	1,620	1,707
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	90	149
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	90	149
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	76	4
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	76	4
Derivative liabilities | Level 3
Fair Value, Assets And Liabilities Measured On Recurring Basis [Line Items]
Derivative liabilities	$ 0	$ 0