Net Income Per Share - Computation of Basic and Diluted Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Numerator:
Net income	$ 84	$ 667
Denominator:
Weighted average shares of common stock - basic (in shares)	1,173	1,171
Dilutive effect of equity incentive awards (in shares)	12	17
Weighted average shares of common stock - diluted (in shares)	1,185	1,188
Net income per share:
Basic (in usd per share)	$ 0.07	$ 0.57
Diluted (in usd per share)	$ 0.07	$ 0.56
Common stock equivalents excluded from income per diluted share because their effect would have been anti-dilutive (in shares)	2	3