Earnings Per Share (Schedule of Earnings Per Share) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net loss	$ (609)	$ 80	$ (880)	$ (1,547)	$ (529)	$ (2,427)
Number of common shares:
Weighted average outstanding (in shares)	676,722,999		541,079,192		676,057,534	540,693,841
Weighted average and potential dilutive outstanding (in shares)	676,722,999		541,079,192		676,057,534	540,693,841
Loss per common share
Basic (in dollars per share)	$ (0.90)		$ (1.63)		$ (0.78)	$ (4.49)
Diluted (in dollars per share)	$ (0.90)		$ (1.63)		$ (0.78)	$ (4.49)
Stock options
Number of common shares:
Issued upon assumed exercise of outstanding stock options (in shares)	0		0		0	0
Restricted Common Stock
Number of common shares:
Effect of issuance of non-vested restricted common stock (in shares)	0		0		0	0
Restricted stock units
Number of common shares:
Effect of issuance of non-vested restricted common stock (in shares)	0		0		0	0
Performance units
Number of common shares:
Effect of issuance of non-vested performance units (in shares)	0		0		0	0