Earnings (Loss) per Common Share - Computation of Basic and Diluted (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2020
Basic EPS:
Net income (loss)	$ 476	$ (1,635)	$ 19	$ (1,250)	$ (1,159)	$ (1,231)
Basic weighted average common shares outstanding (in shares)	650,346		644,123		649,925	639,366
Basic EPS (in dollars per share)	$ 0.73		$ 0.03		$ (1.78)	$ (1.92)
Diluted EPS:
Interest expense on 6.50% convertible senior notes	$ 11		$ 0
Net income (loss) for purposes of computing diluted EPS	$ 487		$ 19		$ (1,159)	$ (1,231)
Dilutive effect of stock awards (in shares)	1,477		1,944		0	0
Dilutive effect of warrants (in shares)	4,981		10,305		0	0
Assumed conversion of 6.50% convertible senior notes (in shares)	61,728		0		0	0
Diluted weighted average common shares outstanding (in shares)	718,532		656,372		649,925	639,366
Diluted EPS (in dollars per share)	$ 0.68		$ 0.03		$ (1.78)	$ (1.92)
6.50% Senior Notes | Senior Notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Fixed interest rate per annum	6.50%				6.50%		6.50%