NET INCOME (LOSS) 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		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Earnings Per Share [Abstract]
Net income (loss) attributable to Gilead	$ 2,592	$ 360	$ 5,843	$ (1,428)
Shares used in per share calculation - basic (in shares)	1,256	1,255	1,256	1,257
Dilutive effect of stock options and equivalents (in shares)	6	6	6	0
Shares used in per share calculation - diluted (in shares)	1,262	1,261	1,262	1,257
Net income (loss) per share attributable to Gilead common stockholders - basic (in dollars per share)	$ 2.06	$ 0.29	$ 4.65	$ (1.14)
Net income (loss) per share attributable to Gilead common stockholders - diluted (in dollars per share)	$ 2.05	$ 0.29	$ 4.63	$ (1.14)