Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ (1,168)	$ 2,099	$ 2,675	$ 5,457
Other comprehensive income (loss):
Net foreign currency translation gain (loss), net of tax	(27)	1	(19)	(17)
Available-for-sale debt securities:
Net unrealized gain, net of tax	4	31	53	25
Reclassifications to net income, net of tax	0	0	0	4
Net change	4	31	53	29
Cash flow hedges:
Net unrealized gain (loss), net of tax	70	(6)	99	51
Reclassifications to net income, net of tax	(32)	8	(96)	101
Net change	38	2	3	152
Other comprehensive income	15	34	37	164
Comprehensive income (loss)	(1,153)	2,133	2,712	5,621
Comprehensive income (loss) attributable to noncontrolling interest	(3)	2	(15)	5
Comprehensive income (loss) attributable to Gilead	$ (1,150)	$ 2,131	$ 2,727	$ 5,616