CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 1,517	$ (3,346)	$ 3,239	$ (1,808)
Other comprehensive income (loss):
Net foreign currency translation gain (loss), net of tax	(5)	4	5	(35)
Available-for-sale debt securities:
Net unrealized gain (loss), net of tax	(1)	74	(3)	51
Reclassifications to net income (loss), net of tax	0	(2)	0	(13)
Net change	(1)	72	(3)	38
Cash flow hedges:
Net unrealized gain (loss), net of tax	(13)	(36)	55	21
Reclassifications to net income (loss), net of tax	20	(16)	42	(39)
Net change	7	(52)	97	(18)
Other comprehensive income (loss)	1	24	99	(15)
Comprehensive income (loss)	1,518	(3,322)	3,338	(1,823)
Comprehensive loss attributable to noncontrolling interest	5	7	12	20
Comprehensive income (loss) attributable to Gilead	$ 1,523	$ (3,315)	$ 3,350	$ (1,803)