Fair Value (Assets and Liabilities Measured at Fair Value on Recurring Basis) (Details) - USD ($) $ in Millions	Jan. 26, 2019	Jul. 28, 2018
Fair Value Measurements [Line Items]
Available-for-sale debt investments	$ 30,486	$ 37,009
Marketable equity securities	62	605
Derivative assets	23	2
Derivative liabilities	40	74
U.S. government securities
Fair Value Measurements [Line Items]
Available-for-sale debt investments	3,472	7,275
U.S. government agency securities
Fair Value Measurements [Line Items]
Available-for-sale debt investments	354	727
Non-U.S. government and agency securities
Fair Value Measurements [Line Items]
Available-for-sale debt investments	115	208
Corporate debt securities
Fair Value Measurements [Line Items]
Available-for-sale debt investments	24,753	27,364
Commercial paper
Fair Value Measurements [Line Items]
Available-for-sale debt investments	243
Certificates of deposit
Fair Value Measurements [Line Items]
Available-for-sale debt investments	115
Fair Value, Measurements, Recurring
Fair Value Measurements [Line Items]
Marketable equity securities	62	605
Derivative assets	23	2
Total	38,583	44,506
Derivative liabilities	40	74
Total	40	74
Fair Value, Measurements, Recurring \| U.S. government securities
Fair Value Measurements [Line Items]
Available-for-sale debt investments	3,472	7,275
Fair Value, Measurements, Recurring \| U.S. government agency securities
Fair Value Measurements [Line Items]
Available-for-sale debt investments	354	727
Fair Value, Measurements, Recurring \| Non-U.S. government and agency securities
Fair Value Measurements [Line Items]
Available-for-sale debt investments	115	208
Fair Value, Measurements, Recurring \| Corporate debt securities
Fair Value Measurements [Line Items]
Available-for-sale debt investments	24,753	27,364
Fair Value, Measurements, Recurring \| U.S. agency mortgage-backed securities
Fair Value Measurements [Line Items]
Available-for-sale debt investments	1,434	1,435
Fair Value, Measurements, Recurring \| Commercial paper
Fair Value Measurements [Line Items]
Available-for-sale debt investments	243	0
Fair Value, Measurements, Recurring \| Certificates of deposit
Fair Value Measurements [Line Items]
Available-for-sale debt investments	115	0
Fair Value, Measurements, Recurring \| Money market funds
Fair Value Measurements [Line Items]
Cash equivalents:	7,888	6,890
Fair Value, Measurements, Recurring \| Commercial paper
Fair Value Measurements [Line Items]
Cash equivalents:	99	0
Fair Value, Measurements, Recurring \| Certificates of deposit
Fair Value Measurements [Line Items]
Cash equivalents:	25	0
Fair Value, Measurements, Recurring \| Level 1
Fair Value Measurements [Line Items]
Marketable equity securities	62	605
Derivative assets	0	0
Total	7,950	7,495
Derivative liabilities	0	0
Total	0	0
Fair Value, Measurements, Recurring \| Level 1 \| U.S. government securities
Fair Value Measurements [Line Items]
Available-for-sale debt investments	0	0
Fair Value, Measurements, Recurring \| Level 1 \| U.S. government agency securities
Fair Value Measurements [Line Items]
Available-for-sale debt investments	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Non-U.S. government and agency securities
Fair Value Measurements [Line Items]
Available-for-sale debt investments	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Corporate debt securities
Fair Value Measurements [Line Items]
Available-for-sale debt investments	0	0
Fair Value, Measurements, Recurring \| Level 1 \| U.S. agency mortgage-backed securities
Fair Value Measurements [Line Items]
Available-for-sale debt investments	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Commercial paper
Fair Value Measurements [Line Items]
Available-for-sale debt investments	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Certificates of deposit
Fair Value Measurements [Line Items]
Available-for-sale debt investments	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Money market funds
Fair Value Measurements [Line Items]
Cash equivalents:	7,888	6,890
Fair Value, Measurements, Recurring \| Level 1 \| Commercial paper
Fair Value Measurements [Line Items]
Cash equivalents:	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Certificates of deposit
Fair Value Measurements [Line Items]
Cash equivalents:	0	0
Fair Value, Measurements, Recurring \| Level 2
Fair Value Measurements [Line Items]
Marketable equity securities	0	0
Derivative assets	23	2
Total	30,633	37,011
Derivative liabilities	40	74
Total	40	74
Fair Value, Measurements, Recurring \| Level 2 \| U.S. government securities
Fair Value Measurements [Line Items]
Available-for-sale debt investments	3,472	7,275
Fair Value, Measurements, Recurring \| Level 2 \| U.S. government agency securities
Fair Value Measurements [Line Items]
Available-for-sale debt investments	354	727
Fair Value, Measurements, Recurring \| Level 2 \| Non-U.S. government and agency securities
Fair Value Measurements [Line Items]
Available-for-sale debt investments	115	208
Fair Value, Measurements, Recurring \| Level 2 \| Corporate debt securities
Fair Value Measurements [Line Items]
Available-for-sale debt investments	24,753	27,364
Fair Value, Measurements, Recurring \| Level 2 \| U.S. agency mortgage-backed securities
Fair Value Measurements [Line Items]
Available-for-sale debt investments	1,434	1,435
Fair Value, Measurements, Recurring \| Level 2 \| Commercial paper
Fair Value Measurements [Line Items]
Available-for-sale debt investments	243	0
Fair Value, Measurements, Recurring \| Level 2 \| Certificates of deposit
Fair Value Measurements [Line Items]
Available-for-sale debt investments	115	0
Fair Value, Measurements, Recurring \| Level 2 \| Money market funds
Fair Value Measurements [Line Items]
Cash equivalents:	0	0
Fair Value, Measurements, Recurring \| Level 2 \| Commercial paper
Fair Value Measurements [Line Items]
Cash equivalents:	99	0
Fair Value, Measurements, Recurring \| Level 2 \| Certificates of deposit
Fair Value Measurements [Line Items]
Cash equivalents:	$ 25	$ 0

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Fair value of financial and nonfinancial obligations.

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