Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ (3,346)	$ 1,875	$ (1,808)	$ 3,843
Other comprehensive income (loss):
Net foreign currency translation gain (loss), net of tax	4	(13)	(35)	8
Available-for-sale debt securities:
Net unrealized gain, net of tax	74	19	51	49
Reclassifications to net income (loss), net of tax	(2)	0	(13)	0
Net change	72	19	38	49
Cash flow hedges:
Net unrealized gain (loss), net of tax	(36)	1	21	29
Reclassifications to net income (loss), net of tax	(16)	(35)	(39)	(64)
Net change	(52)	(34)	(18)	(35)
Other comprehensive income (loss)	24	(28)	(15)	22
Comprehensive income (loss)	(3,322)	1,847	(1,823)	3,865
Less: Comprehensive loss attributable to noncontrolling interest	(7)	(5)	(20)	(12)
Comprehensive income (loss) attributable to Gilead	$ (3,315)	$ 1,852	$ (1,803)	$ 3,877