Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 353	$ (1,168)	$ (1,455)	$ 2,675
Other comprehensive income (loss):
Net foreign currency translation gain (loss), net of tax	23	(27)	(12)	(19)
Available-for-sale debt securities:
Unrealized gain (loss), net of tax	(9)	4	42	53
Reclassifications to net income (loss), net of tax	(4)	0	(17)	0
Net change	(13)	4	25	53
Cash flow hedges:
Unrealized gain (loss), net of tax	(46)	70	(25)	99
Reclassifications to net income (loss), net of tax	(11)	(32)	(50)	(96)
Net change	(57)	38	(75)	3
Other comprehensive income (loss)	(47)	15	(62)	37
Comprehensive income (loss)	306	(1,153)	(1,517)	2,712
Less: Comprehensive (loss) attributable to noncontrolling interest	(7)	(3)	(27)	(15)
Comprehensive income (loss) attributable to Gilead	$ 313	$ (1,150)	$ (1,490)	$ 2,727