Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 5,364	$ 5,460	$ 4,644
Other Comprehensive Income (Loss)
Net foreign currency translation gain (loss), net of tax	6	(38)	(47)
Available-for-sale Securities
Net unrealized gain, net of tax	54	43	218
Reclassifications to net income, net of tax	(1)	4	(8)
Net change	53	47	210
Cash Flow Hedges
Net unrealized gain (loss), net of tax	72	112	(304)
Reclassification to net income, net of tax	(126)	87	28
Net change	(54)	199	(276)
Other comprehensive income (loss)	5	208	(113)
Comprehensive income	5,369	5,668	4,531
Comprehensive (loss) income attributable to noncontrolling interest	(22)	5	16
Comprehensive income attributable to Gilead	$ 5,391	$ 5,663	$ 4,515