Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 4,644	$ 13,488	$ 18,106
Other Comprehensive Income (Loss)
Net foreign currency translation gain (loss), net of tax	(47)	177	9
Available-for-sale Securities
Net unrealized gain (loss), net of tax impact of $6, $19 and $(17), respectively	218	7	(29)
Reclassifications to net income, net of tax impact of $(9), $0 and $1, respectively	(8)	(7)	1
Net change	210	0	(28)
Cash Flow Hedges
Net unrealized gain (loss), net of tax impact of $(11), $0 and $21, respectively	(304)	5	389
Reclassification to net income, net of tax impact of $0, $(8) and $(19), respectively	28	8	(583)
Net change	(276)	13	(194)
Other comprehensive income (loss)	(113)	190	(213)
Comprehensive income	4,531	13,678	17,893
Comprehensive income (loss) attributable to noncontrolling interest	16	(13)	(2)
Comprehensive income attributable to Gilead	$ 4,515	$ 13,691	$ 17,895