Fair Value - Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Millions	Oct. 24, 2020	Jul. 25, 2020
Assets:
Available-for-sale debt investments:	$ 19,190	$ 17,610
U.S. government securities
Assets:
Available-for-sale debt investments:	2,717	2,685
U.S. government agency securities
Assets:
Available-for-sale debt investments:	178	110
Corporate debt securities
Assets:
Available-for-sale debt investments:	11,537	11,877
Commercial paper
Assets:
Available-for-sale debt investments:	1,712	727
Certificates of deposit
Assets:
Available-for-sale debt investments:	517	176
Fair value, measurements, recurring
Assets:
Assets:	182	191
Total	28,130	27,833
Liabilities:
Derivative liabilities	22	10
Total	22	10
Fair value, measurements, recurring \| U.S. government securities
Assets:
Available-for-sale debt investments:	2,717	2,685
Fair value, measurements, recurring \| U.S. government agency securities
Assets:
Available-for-sale debt investments:	178	110
Fair value, measurements, recurring \| Corporate debt securities
Assets:
Available-for-sale debt investments:	11,537	11,877
Fair value, measurements, recurring \| U.S. agency mortgage-backed securities
Assets:
Available-for-sale debt investments:	2,529	2,035
Fair value, measurements, recurring \| Commercial paper
Assets:
Available-for-sale debt investments:	1,712	727
Fair value, measurements, recurring \| Certificates of deposit
Assets:
Available-for-sale debt investments:	517	176
Fair value, measurements, recurring \| Money market funds
Assets:
Cash equivalents:	8,634	10,024
Fair value, measurements, recurring \| Corporate debt securities
Assets:
Cash equivalents:	4	8
Fair value, measurements, recurring \| Commercial paper
Assets:
Cash equivalents:	120	0
Fair value, measurements, recurring \| Level 1
Assets:
Assets:	0	0
Total	8,634	10,024
Liabilities:
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:	8,634	10,024
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:
Assets:	179	190
Total	19,493	17,808
Liabilities:
Derivative liabilities	22	10
Total	22	10
Fair value, measurements, recurring \| Level 2 \| U.S. government securities
Assets:
Available-for-sale debt investments:	2,717	2,685
Fair value, measurements, recurring \| Level 2 \| U.S. government agency securities
Assets:
Available-for-sale debt investments:	178	110
Fair value, measurements, recurring \| Level 2 \| Corporate debt securities
Assets:
Available-for-sale debt investments:	11,537	11,877
Fair value, measurements, recurring \| Level 2 \| U.S. agency mortgage-backed securities
Assets:
Available-for-sale debt investments:	2,529	2,035
Fair value, measurements, recurring \| Level 2 \| Commercial paper
Assets:
Available-for-sale debt investments:	1,712	727
Fair value, measurements, recurring \| Level 2 \| Certificates of deposit
Assets:
Available-for-sale debt investments:	517	176
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:	4	8
Fair value, measurements, recurring \| Level 2 \| Commercial paper
Assets:
Cash equivalents:	120	0
Fair value, measurements, recurring \| Level 3
Assets:
Assets:	3	1
Total	3	1
Liabilities:
Derivative liabilities	0	0
Total	0	0
Fair value, measurements, recurring \| Level 3 \| U.S. government securities
Assets:
Available-for-sale debt investments:	0	0
Fair value, measurements, recurring \| Level 3 \| U.S. government agency securities
Assets:
Available-for-sale debt investments:	0	0
Fair value, measurements, recurring \| Level 3 \| Corporate debt securities
Assets:
Available-for-sale debt investments:	0	0
Fair value, measurements, recurring \| Level 3 \| U.S. agency mortgage-backed securities
Assets:
Available-for-sale debt investments:	0	0
Fair value, measurements, recurring \| Level 3 \| Commercial paper
Assets:
Available-for-sale debt investments:	0	0
Fair value, measurements, recurring \| Level 3 \| Certificates of deposit
Assets:
Available-for-sale debt investments:	0	0
Fair value, measurements, recurring \| Level 3 \| Money market funds
Assets:
Cash equivalents:	0	0
Fair value, measurements, recurring \| Level 3 \| Corporate debt securities
Assets:
Cash equivalents:	0	0
Fair value, measurements, recurring \| Level 3 \| Commercial paper
Assets:
Cash equivalents:	$ 0	$ 0

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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

+ Details

Name:	us-gaap_AssetsFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

Name:	us-gaap_AssetsFairValueDisclosureAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(6))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=121558606&loc=SL82898722-210454

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121553693&loc=d3e26610-111562

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27161-111563

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesDebtSecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

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.

+ References

No definition available.

+ Details

Name:	us-gaap_CashAndCashEquivalentsFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226008-175313

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=121572278&loc=d3e13433-108611

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

+ Details

Name:	us-gaap_DerivativeAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value, after the effects of master netting arrangements, of a financial liability or 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 liabilities not subject to a master netting arrangement and not elected to be offset.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=121572278&loc=d3e13433-108611

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226008-175313

+ Details

Name:	us-gaap_DerivativeLiabilities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Fair value of financial and nonfinancial obligations.

+ References

+ Details

Name:	us-gaap_LiabilitiesFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- References

No definition available.

+ Details

Name:	us-gaap_LiabilitiesFairValueDisclosureAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_USTreasuryAndGovernmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_CommercialPaperMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_CertificatesOfDepositMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CashAndCashEquivalentsAxis=us-gaap_MoneyMarketFundsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CashAndCashEquivalentsAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CashAndCashEquivalentsAxis=us-gaap_CommercialPaperMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: