Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 5,460	$ 4,644	$ 13,488
Other Comprehensive Income (Loss)
Net foreign currency translation gain (loss), net of tax	(38)	(47)	177
Available-for-sale Securities
Net unrealized gain, net of tax impact of $0, $6 and $19, respectively	43	218	7
Reclassifications to net income (loss), net of tax impact of $0, ($9) and $0, respectively	4	(8)	(7)
Net change	47	210	0
Cash Flow Hedges
Net unrealized gain (loss), net of tax impact of $2, ($11) and $0, respectively	112	(304)	5
Reclassification to net income, net of tax impact of $0, $0 and $(8), respectively	87	28	8
Net change	199	(276)	13
Other comprehensive income (loss)	208	(113)	190
Comprehensive income	5,668	4,531	13,678
Comprehensive income (loss) attributable to noncontrolling interest	5	16	(13)
Comprehensive income attributable to Gilead	$ 5,663	$ 4,515	$ 13,691