Net Income Per Share Attributable to Gilead Common Stockholders - Schedule of the Calculation of Basic and Diluted EPS (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share [Abstract]
Net income attributable to Gilead	$ 1,538	$ 2,702
Shares used in per share calculation - basic (in shares)	1,307	1,308
Effect of dilutive securities:
Stock options and equivalents (in shares)	13	12
Shares used in per share calculation - diluted (in shares)	1,320	1,320
Net income per share attributable to Gilead common stockholders - basic (usd per share)	$ 1.18	$ 2.07
Net income per share attributable to Gilead common stockholders - diluted (usd per share)	$ 1.17	$ 2.05