Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 1,968	$ 1,539
Other comprehensive income (loss):
Net foreign currency translation gain, net of tax	21	7
Available-for-sale debt securities:
Net unrealized gain (loss), net of tax	30	(36)
Reclassifications to net income, net of tax	0	0
Net change	30	(36)
Cash flow hedges:
Net unrealized gain (loss), net of tax	28	(61)
Reclassifications to net income, net of tax	(29)	48
Net change	(1)	(13)
Other comprehensive income (loss)	50	(42)
Comprehensive income	2,018	1,497
Comprehensive income (loss) attributable to noncontrolling interest	(7)	1
Comprehensive income attributable to Gilead	$ 2,025	$ 1,496