FAIR VALUE MEASUREMENTS - Summary of Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Assets:
Available-for-sale debt securities	$ 2,290	$ 2,497
MYR GmbH
Liabilities:
Liability for MYR GmbH (“MYR”) contingent consideration	249
Other publicly traded equity securities
Assets:
Total	4,793	5,743
Fair Value, Measurements, Recurring \| Estimate of Fair Value Measurement
Assets:
Total	7,325	8,320
Liabilities:
Total	458	583
Fair Value, Measurements, Recurring \| Estimate of Fair Value Measurement \| MYR GmbH
Liabilities:
Liability for MYR GmbH (“MYR”) contingent consideration	249	317
Fair Value, Measurements, Recurring \| Estimate of Fair Value Measurement \| U.S. treasury securities
Assets:
Available-for-sale debt securities	448	407
Fair Value, Measurements, Recurring \| Estimate of Fair Value Measurement \| U.S. government agencies securities
Assets:
Available-for-sale debt securities	19	4
Fair Value, Measurements, Recurring \| Estimate of Fair Value Measurement \| Non-U.S. government securities
Assets:
Available-for-sale debt securities	44	50
Fair Value, Measurements, Recurring \| Estimate of Fair Value Measurement \| Certificates of deposit
Assets:
Available-for-sale debt securities	65	249
Fair Value, Measurements, Recurring \| Estimate of Fair Value Measurement \| Corporate debt securities
Assets:
Available-for-sale debt securities	1,367	1,363
Fair Value, Measurements, Recurring \| Estimate of Fair Value Measurement \| Residential mortgage and asset-backed securities
Assets:
Available-for-sale debt securities	347	424
Fair Value, Measurements, Recurring \| Estimate of Fair Value Measurement \| Money market funds
Assets:
Marketable equity securities	3,316	3,661
Fair Value, Measurements, Recurring \| Estimate of Fair Value Measurement \| Other publicly traded equity securities
Assets:
Marketable equity securities	205	331
Fair Value, Measurements, Recurring \| Estimate of Fair Value Measurement \| Other publicly traded equity securities \| Galapagos
Assets:
Marketable equity securities	703	931
Fair Value, Measurements, Recurring \| Estimate of Fair Value Measurement \| Other publicly traded equity securities \| Arcus
Assets:
Marketable equity securities	361	559
Fair Value, Measurements, Recurring \| Estimate of Fair Value Measurement \| Deferred compensation plan
Assets:
Marketable equity securities	208	261
Liabilities:
Deferred compensation plan	208	261
Fair Value, Measurements, Recurring \| Estimate of Fair Value Measurement \| Foreign currency derivative contracts
Assets:
Foreign currency derivative contracts	242	80
Liabilities:
Foreign currency derivative contracts	2	5
Fair Value, Measurements, Recurring \| Level 1
Assets:
Total	5,242	6,150
Liabilities:
Total	208	261
Fair Value, Measurements, Recurring \| Level 1 \| MYR GmbH
Liabilities:
Liability for MYR GmbH (“MYR”) contingent consideration	0	0
Fair Value, Measurements, Recurring \| Level 1 \| U.S. treasury securities
Assets:
Available-for-sale debt securities	448	407
Fair Value, Measurements, Recurring \| Level 1 \| U.S. government agencies securities
Assets:
Available-for-sale debt securities	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Non-U.S. government securities
Assets:
Available-for-sale debt securities	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Certificates of deposit
Assets:
Available-for-sale debt securities	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Corporate debt securities
Assets:
Available-for-sale debt securities	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Residential mortgage and asset-backed securities
Assets:
Available-for-sale debt securities	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Money market funds
Assets:
Marketable equity securities	3,316	3,661
Fair Value, Measurements, Recurring \| Level 1 \| Other publicly traded equity securities
Assets:
Marketable equity securities	205	331
Fair Value, Measurements, Recurring \| Level 1 \| Other publicly traded equity securities \| Galapagos
Assets:
Marketable equity securities	703	931
Fair Value, Measurements, Recurring \| Level 1 \| Other publicly traded equity securities \| Arcus
Assets:
Marketable equity securities	361	559
Fair Value, Measurements, Recurring \| Level 1 \| Deferred compensation plan
Assets:
Marketable equity securities	208	261
Liabilities:
Deferred compensation plan	208	261
Fair Value, Measurements, Recurring \| Level 1 \| Foreign currency derivative contracts
Assets:
Foreign currency derivative contracts	0	0
Liabilities:
Foreign currency derivative contracts	0	0
Fair Value, Measurements, Recurring \| Level 2
Assets:
Total	2,084	2,170
Liabilities:
Total	2	5
Fair Value, Measurements, Recurring \| Level 2 \| MYR GmbH
Liabilities:
Liability for MYR GmbH (“MYR”) contingent consideration	0	0
Fair Value, Measurements, Recurring \| Level 2 \| U.S. treasury securities
Assets:
Available-for-sale debt securities	0	0
Fair Value, Measurements, Recurring \| Level 2 \| U.S. government agencies securities
Assets:
Available-for-sale debt securities	19	4
Fair Value, Measurements, Recurring \| Level 2 \| Non-U.S. government securities
Assets:
Available-for-sale debt securities	44	50
Fair Value, Measurements, Recurring \| Level 2 \| Certificates of deposit
Assets:
Available-for-sale debt securities	65	249
Fair Value, Measurements, Recurring \| Level 2 \| Corporate debt securities
Assets:
Available-for-sale debt securities	1,367	1,363
Fair Value, Measurements, Recurring \| Level 2 \| Residential mortgage and asset-backed securities
Assets:
Available-for-sale debt securities	347	424
Fair Value, Measurements, Recurring \| Level 2 \| Money market funds
Assets:
Marketable equity securities	0	0
Fair Value, Measurements, Recurring \| Level 2 \| Other publicly traded equity securities
Assets:
Marketable equity securities	0	0
Fair Value, Measurements, Recurring \| Level 2 \| Other publicly traded equity securities \| Galapagos
Assets:
Marketable equity securities	0	0
Fair Value, Measurements, Recurring \| Level 2 \| Other publicly traded equity securities \| Arcus
Assets:
Marketable equity securities	0	0
Fair Value, Measurements, Recurring \| Level 2 \| Deferred compensation plan
Assets:
Marketable equity securities	0	0
Liabilities:
Deferred compensation plan	0	0
Fair Value, Measurements, Recurring \| Level 2 \| Foreign currency derivative contracts
Assets:
Foreign currency derivative contracts	242	80
Liabilities:
Foreign currency derivative contracts	2	5
Fair Value, Measurements, Recurring \| Level 3
Assets:
Total	0	0
Liabilities:
Total	249	317
Fair Value, Measurements, Recurring \| Level 3 \| MYR GmbH
Liabilities:
Liability for MYR GmbH (“MYR”) contingent consideration	249	317
Fair Value, Measurements, Recurring \| Level 3 \| U.S. treasury securities
Assets:
Available-for-sale debt securities	0	0
Fair Value, Measurements, Recurring \| Level 3 \| U.S. government agencies securities
Assets:
Available-for-sale debt securities	0	0
Fair Value, Measurements, Recurring \| Level 3 \| Non-U.S. government securities
Assets:
Available-for-sale debt securities	0	0
Fair Value, Measurements, Recurring \| Level 3 \| Certificates of deposit
Assets:
Available-for-sale debt securities	0	0
Fair Value, Measurements, Recurring \| Level 3 \| Corporate debt securities
Assets:
Available-for-sale debt securities	0	0
Fair Value, Measurements, Recurring \| Level 3 \| Residential mortgage and asset-backed securities
Assets:
Available-for-sale debt securities	0	0
Fair Value, Measurements, Recurring \| Level 3 \| Money market funds
Assets:
Marketable equity securities	0	0
Fair Value, Measurements, Recurring \| Level 3 \| Other publicly traded equity securities
Assets:
Marketable equity securities	0	0
Fair Value, Measurements, Recurring \| Level 3 \| Other publicly traded equity securities \| Galapagos
Assets:
Marketable equity securities	0	0
Fair Value, Measurements, Recurring \| Level 3 \| Other publicly traded equity securities \| Arcus
Assets:
Marketable equity securities	0	0
Fair Value, Measurements, Recurring \| Level 3 \| Deferred compensation plan
Assets:
Marketable equity securities	0	0
Liabilities:
Deferred compensation plan	0	0
Fair Value, Measurements, Recurring \| Level 3 \| Foreign currency derivative contracts
Assets:
Foreign currency derivative contracts	0	0
Liabilities:
Foreign currency derivative contracts	$ 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 https://asc.fasb.org/extlink&oid=126976982&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 liability recognized arising from contingent consideration in a business combination.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-URI https://asc.fasb.org/extlink&oid=126975305&loc=d3e6927-128479

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 35
-Paragraph 1
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126966325&loc=d3e6819-128478

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 25
-Paragraph 6
-URI https://asc.fasb.org/extlink&oid=6911189&loc=d3e6408-128476

+ Details

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

- Definition

Amount excluding accrued interest, 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/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=124258926&loc=SL82898722-210454

+ Details

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

- Definition

Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI), classified as current.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(2))
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (f)
-URI https://asc.fasb.org/extlink&oid=124098289&loc=d3e6676-107765

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 45
-Paragraph 1A
-URI https://asc.fasb.org/extlink&oid=123594786&loc=SL75136599-209740

+ Details

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

- Definition

Fair value portion of asset contracts related to the exchange of different currencies, including, but not limited to, foreign currency options, forward contracts, and swaps.

+ References

No definition available.

+ Details

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

- Definition

Fair value portion of liability contracts related to the exchange of different currencies, including, but not limited to, foreign currency options, forward (delivery or nondelivery) contracts, and swaps entered into.

+ References

No definition available.

+ Details

Name:	us-gaap_ForeignCurrencyContractsLiabilityFairValueDisclosure
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

- Definition

Fair value portion of other liabilities.

+ References

No definition available.

+ Details

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

- Details

Name:	us-gaap_BusinessAcquisitionAxis=gild_MYRGmbHMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=us-gaap_EquitySecuritiesMember
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_FairValueByMeasurementBasisAxis=us-gaap_EstimateOfFairValueFairValueDisclosureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=us-gaap_USTreasurySecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_FairValueByAssetClassAxis=us-gaap_ForeignGovernmentDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

Name:	us-gaap_FairValueByAssetClassAxis=gild_ResidentialMortgageAndAssetBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=gild_GalapagosMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=gild_ArcusBiosciencesIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=gild_DeferredCompensationPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=gild_ForeignCurrencyDerivativeContractsMember
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: