Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 1,875	$ 1,819	$ 3,843	$ 3,358
Other comprehensive income (loss):
Net foreign currency translation gain (loss), net of tax	(13)	(25)	8	(18)
Available-for-sale debt securities:
Net unrealized gain (loss), net of tax	19	30	49	(6)
Reclassifications to net income, net of tax	0	4	0	4
Net change	19	34	49	(2)
Cash flow hedges:
Net unrealized gain, net of tax	1	118	29	57
Reclassifications to net income, net of tax	(35)	45	(64)	93
Net change	(34)	163	(35)	150
Other comprehensive income (loss)	(28)	172	22	130
Comprehensive income	1,847	1,991	3,865	3,488
Comprehensive income (loss) attributable to noncontrolling interest	(5)	2	(12)	3
Comprehensive income attributable to Gilead	$ 1,852	$ 1,989	$ 3,877	$ 3,485