Earnings (Loss) Per Share - Computation of Basic and Diluted Earnings Per Share (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]
Earnings (loss) available to common stockholders, basic	$ 473	$ (1,841)	$ (1,318)	$ (5,172)
Earnings (loss) available to common stockholders, diluted	$ 473	$ (1,841)	$ (1,318)	$ (5,172)
Basic weighted-average shares outstanding (in shares)	323.7	291.0	321.3	273.5
Dilutive effect of employee stock awards (in shares)	3.0	0.0	0.0	0.0
Dilutive effect of stock warrants (in shares)	2.3	0.0	0.0	0.0
Diluted weighted-average shares outstanding (in shares)	329.0	291.0	321.3	273.5
Earnings (loss) per share, basic (in dollars per share)	$ 1.46	$ (6.33)	$ (4.10)	$ (18.91)
Earnings (loss) per share, diluted ( in dollars per share)	$ 1.44	$ (6.33)	$ (4.10)	$ (18.91)