Loss Per Share - Computation of Basic and Diluted Earnings Per Share (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]
Loss available to common stockholders, basic	$ (434)	$ (1,627)	$ (1,791)	$ (3,331)
Loss available to common stockholders, diluted	$ (434)	$ (1,627)	$ (1,791)	$ (3,331)
Basic weighted-average shares outstanding (in shares)	323.6	280.7	320.1	264.6
Diluted weighted-average shares outstanding (in shares)	323.6	280.7	320.1	264.6
Loss per share, basic (in dollars per share)	$ (1.34)	$ (5.79)	$ (5.60)	$ (12.59)
Loss per share, diluted (in dollars per share)	$ (1.34)	$ (5.79)	$ (5.60)	$ (12.59)