Net Income (Loss) Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
NUMERATOR:
Net income (loss)	$ (94)	$ 387
DENOMINATOR:
Weighted-average shares outstanding, basic	515	551
Dilutive effect of restricted stock units	0	1
Adjusted weighted-average shares outstanding, diluted	515	552
NET INCOME (LOSS) PER SHARE:
Basic	$ (0.18)	$ 0.70
Diluted	$ (0.18)	$ 0.70