Debt Instrument, Call Feature, Period Before Maturity

No definition available.

Name:	gild_DebtInstrumentCallFeaturePeriodBeforeMaturity
Namespace Prefix:	gild_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt Instrument, Redemption Price, Basis Spread On Variable Rate To Discount Remaining Payments

+ References

No definition available.

+ Details

Name:	gild_DebtInstrumentRedemptionPriceBasisSpreadOnVariableRateToDiscountRemainingPayments
Namespace Prefix:	gild_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

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

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

- Definition

Percentage price of original principal amount of debt at which debt can be redeemed by the issuer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-Subparagraph e
-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

+ Details

Name:	us-gaap_DebtInstrumentRedemptionPricePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

+ Details

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

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031897-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

The cash outflow to repay long-term debt that is not secured by collateral. Excludes repayments of tax exempt unsecured debt.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3291-108585

+ Details

Name:	us-gaap_RepaymentsOfUnsecuredDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Debt and Credit Facilities - Additional Information (Details) - USD ($)	1 Months Ended
	Sep. 30, 2020	Feb. 29, 2020	Oct. 23, 2020	Jun. 30, 2020	Dec. 31, 2019
Revolving Credit Facility
Debt Instrument [Line Items]
Amounts outstanding under revolving credit facilities	$ 0				$ 0
Revolving Credit Facility \| the "2016 Revolving Credit Facility"
Debt Instrument [Line Items]
Maximum borrowing capacity				$ 2,500,000,000
Revolving Credit Facility \| the "2020 Revolving Credit Facility"
Debt Instrument [Line Items]
Maximum borrowing capacity				$ 2,500,000,000
Senior Notes \| the "2020 Senior Notes"
Debt Instrument [Line Items]
Principal amount	$ 7,250,000,000
Debt instrument, redemption percentage	101.00%
Senior Notes \| 0.15% LIBOR Senior Unsecured Notes Due September 2021
Debt Instrument [Line Items]
Principal amount	$ 500,000,000
Outstanding borrowings	499,000,000				0
Senior Notes \| 0.52% LIBOR Senior Unsecured Notes Due September 2023
Debt Instrument [Line Items]
Principal amount	$ 500,000,000
Call feature, period prior to maturity	2 years
Outstanding borrowings	$ 496,000,000				0
Senior Notes \| 0.75% Senior Unsecured Notes Due September 2023
Debt Instrument [Line Items]
Principal amount	$ 2,000,000,000.0
Interest rate, stated percentage	0.75%
Outstanding borrowings	$ 1,992,000,000				0
Senior Notes \| 0.75% Senior Unsecured Notes Due September 2023 \| Treasury Rate
Debt Instrument [Line Items]
Basis spread on variable rate to discount remaining payments	0.10%
Senior Notes \| 1.20% Senior Unsecured Notes Due October 2027
Debt Instrument [Line Items]
Principal amount	$ 750,000,000
Interest rate, stated percentage	1.20%
Outstanding borrowings	$ 745,000,000				0
Senior Notes \| 1.20% Senior Unsecured Notes Due October 2027 \| Treasury Rate
Debt Instrument [Line Items]
Basis spread on variable rate to discount remaining payments	0.125%
Senior Notes \| 1.65% Senior Unsecured Notes Due October 2030
Debt Instrument [Line Items]
Principal amount	$ 1,000,000,000.0
Interest rate, stated percentage	1.65%
Outstanding borrowings	$ 992,000,000				0
Senior Notes \| 1.65% Senior Unsecured Notes Due October 2030 \| Treasury Rate
Debt Instrument [Line Items]
Basis spread on variable rate to discount remaining payments	0.15%
Senior Notes \| 2.60% Senior Unsecured Notes Due October 2040
Debt Instrument [Line Items]
Principal amount	$ 1,000,000,000.0
Interest rate, stated percentage	2.60%
Outstanding borrowings	$ 986,000,000				0
Senior Notes \| 2.60% Senior Unsecured Notes Due October 2040 \| Treasury Rate
Debt Instrument [Line Items]
Basis spread on variable rate to discount remaining payments	0.20%
Senior Notes \| 2.80% Senior Unsecured Notes Due October 2050
Debt Instrument [Line Items]
Principal amount	$ 1,500,000,000
Interest rate, stated percentage	2.80%
Outstanding borrowings	$ 1,475,000,000				$ 0
Senior Notes \| 2.80% Senior Unsecured Notes Due October 2050 \| Treasury Rate
Debt Instrument [Line Items]
Basis spread on variable rate to discount remaining payments	0.25%
Senior Notes \| the "2020 Fixed Rate Notes"
Debt Instrument [Line Items]
Debt instrument, redemption percentage	100.00%
Senior Notes \| the "2020 Fixed Rate Notes" \| Minimum
Debt Instrument [Line Items]
Call feature, period prior to maturity	2 months
Senior Notes \| the "2020 Fixed Rate Notes" \| Maximum
Debt Instrument [Line Items]
Call feature, period prior to maturity	2 years
Senior Notes \| the "2014 Senior Notes"
Debt Instrument [Line Items]
Repayments of senior unsecured notes		$ 500,000,000
Senior Notes \| the "2015 Senior Notes"
Debt Instrument [Line Items]
Repayments of senior unsecured notes	$ 2,000,000,000.0
Medium-term Notes \| Three-Year Senior Term Loan Facility
Debt Instrument [Line Items]
Contractual term	3 years
Maximum borrowing capacity	$ 1,000,000,000.0
Outstanding borrowings	$ 0
Medium-term Notes \| Three-Year Senior Term Loan Facility \| Subsequent Event
Debt Instrument [Line Items]
Principal amount			$ 1,000,000,000.0