Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 1,539	$ 2,699
Other comprehensive income (loss):
Net foreign currency translation gain (loss), net of tax	7	(76)
Available-for-sale securities:
Net unrealized gain (loss), net of tax impact of $0 and $2, respectively	(36)	184
Reclassifications to net income, net of tax impact of $0 and $0, respectively	0	3
Net change	(36)	187
Cash flow hedges:
Net unrealized loss, net of tax impact of $0 and $(7), respectively	(61)	(87)
Reclassifications to net income, net of tax impact of $0 and $(1), respectively	48	(42)
Net change	(13)	(129)
Other comprehensive loss	(42)	(18)
Comprehensive income	1,497	2,681
Comprehensive income (loss) attributable to noncontrolling interest	1	(3)
Comprehensive income attributable to Gilead	$ 1,496	$ 2,684

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Other Comprehensive Income
-URI http://asc.fasb.org/extlink&oid=51831270

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Comprehensive Income
-URI http://asc.fasb.org/extlink&oid=51831223

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=66004124&loc=d3e557-108580

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Net Income
-URI http://asc.fasb.org/extlink&oid=51831255