Earnings Per Share (Schedule of Earnings Per Share) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income (loss)	$ 80	$ (1,547)
Number of common shares:
Weighted average outstanding (in shares)	675,385,145	540,308,491
Weighted average and potential dilutive outstanding (in shares)	679,867,825	540,308,491
Earnings per common share
Basic (in dollars per share)	$ 0.12	$ (2.86)
Diluted (in dollars per share)	$ 0.12	$ (2.86)
Stock options
Number of common shares:
Issued upon assumed exercise of outstanding stock options (in shares)	0	0
Restricted Common Stock
Number of common shares:
Effect of issuance of non-vested restricted common stock (in shares)	870,541	0
Restricted stock units
Number of common shares:
Effect of issuance of non-vested restricted common stock (in shares)	804,944	0
Performance units
Number of common shares:
Effect of issuance of non-vested performance units (in shares)	2,807,195	0