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		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Earnings Per Share [Abstract]
Net income (loss) attributable to Gilead	$ 1,522	$ (3,339)	$ 3,251	$ (1,788)
Shares used in per share calculation - basic (in shares)	1,255	1,255	1,256	1,258
Dilutive effect of stock options and equivalents (in shares)	5	0	5	0
Shares used in per share calculation - diluted (in shares)	1,260	1,255	1,261	1,258
Net income (loss) per share attributable to Gilead common stockholders - basic (in dollars per share)	$ 1.21	$ (2.66)	$ 2.59	$ (1.42)
Net income (loss) per share attributable to Gilead common stockholders - diluted (in dollars per share)	$ 1.21	$ (2.66)	$ 2.58	$ (1.42)