Fair Value - Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Millions	Oct. 26, 2019	Jul. 27, 2019
Assets:
Available-for-sale debt investments	$ 19,445	$ 21,660
Marketable equity securities	3	3
U.S. government securities
Assets:
Available-for-sale debt investments	1,324	808
U.S. government agency securities
Assets:
Available-for-sale debt investments	98	169
Corporate debt securities
Assets:
Available-for-sale debt investments	16,199	19,262
Commercial paper
Assets:
Available-for-sale debt investments	283
Certificates of deposit
Assets:
Available-for-sale debt investments	31
Fair Value, Measurements, Recurring
Assets:
Marketable equity securities	3	3
Derivative assets	103	89
Total	26,349	31,835
Liabilities, Fair Value Disclosure [Abstract]
Derivative liabilities	8	15
Total	8	15
Fair Value, Measurements, Recurring \| U.S. government securities
Assets:
Available-for-sale debt investments	1,324	808
Fair Value, Measurements, Recurring \| U.S. government agency securities
Assets:
Available-for-sale debt investments	98	169
Fair Value, Measurements, Recurring \| Corporate debt securities
Assets:
Available-for-sale debt investments	16,199	19,262
Fair Value, Measurements, Recurring \| U.S. agency mortgage-backed securities
Assets:
Available-for-sale debt investments	1,510	1,421
Fair Value, Measurements, Recurring \| Commercial paper
Assets:
Available-for-sale debt investments	283	0
Fair Value, Measurements, Recurring \| Certificates of deposit
Assets:
Available-for-sale debt investments	31	0
Fair Value, Measurements, Recurring \| Money market funds
Assets:
Cash equivalents:	6,648	10,083
Fair Value, Measurements, Recurring \| Corporate debt securities
Assets:
Cash equivalents:	90	0
Fair Value, Measurements, Recurring \| Commercial paper
Assets:
Cash equivalents:	60	0
Fair Value, Measurements, Recurring \| Level 1
Assets:
Marketable equity securities	3	3
Derivative assets	0	0
Total	6,651	10,086
Liabilities, Fair Value Disclosure [Abstract]
Derivative liabilities	0	0
Total	0	0
Fair Value, Measurements, Recurring \| Level 1 \| U.S. government securities
Assets:
Available-for-sale debt investments	0	0
Fair Value, Measurements, Recurring \| Level 1 \| U.S. government agency securities
Assets:
Available-for-sale debt investments	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Corporate debt securities
Assets:
Available-for-sale debt investments	0	0
Fair Value, Measurements, Recurring \| Level 1 \| U.S. agency mortgage-backed securities
Assets:
Available-for-sale debt investments	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Commercial paper
Assets:
Available-for-sale debt investments	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Certificates of deposit
Assets:
Available-for-sale debt investments	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Money market funds
Assets:
Cash equivalents:	6,648	10,083
Fair Value, Measurements, Recurring \| Level 1 \| Corporate debt securities
Assets:
Cash equivalents:	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Commercial paper
Assets:
Cash equivalents:	0	0
Fair Value, Measurements, Recurring \| Level 2
Assets:
Marketable equity securities	0	0
Derivative assets	103	89
Total	19,698	21,749
Liabilities, Fair Value Disclosure [Abstract]
Derivative liabilities	8	15
Total	8	15
Fair Value, Measurements, Recurring \| Level 2 \| U.S. government securities
Assets:
Available-for-sale debt investments	1,324	808
Fair Value, Measurements, Recurring \| Level 2 \| U.S. government agency securities
Assets:
Available-for-sale debt investments	98	169
Fair Value, Measurements, Recurring \| Level 2 \| Corporate debt securities
Assets:
Available-for-sale debt investments	16,199	19,262
Fair Value, Measurements, Recurring \| Level 2 \| U.S. agency mortgage-backed securities
Assets:
Available-for-sale debt investments	1,510	1,421
Fair Value, Measurements, Recurring \| Level 2 \| Commercial paper
Assets:
Available-for-sale debt investments	283	0
Fair Value, Measurements, Recurring \| Level 2 \| Certificates of deposit
Assets:
Available-for-sale debt investments	31	0
Fair Value, Measurements, Recurring \| Level 2 \| Money market funds
Assets:
Cash equivalents:	0	0
Fair Value, Measurements, Recurring \| Level 2 \| Corporate debt securities
Assets:
Cash equivalents:	90	0
Fair Value, Measurements, Recurring \| Level 2 \| Commercial paper
Assets:
Cash equivalents:	$ 60	$ 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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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Fair value of financial and nonfinancial obligations.

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