Note 6 - Earnings (Loss) Per Common Share - Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended
		Mar. 31, 2021	Mar. 31, 2020
Net income (loss)		$ 599	$ (96)
Less: Series A convertible preferred stock dividend		24	24
Net income (loss) available to common stockholders – basic		575	(120)
Plus: Series A convertible preferred stock dividend		24
Net income (loss) available to common stockholders – diluted		$ 599	$ (120)
Weighted-average common shares outstanding – basic (in shares)		766	760
Effect of dilutive securities:
Effect of dilutive securities (in shares)		17
Weighted-average common shares outstanding – diluted (in shares)		898	760
Basic (Note 6) (in dollars per share)		$ 0.75	$ (0.16)
Diluted (Note 6) (in dollars per share)		$ 0.67	$ (0.16)
Total (in shares)		1	126
Series A Convertible Preferred Stock [Member]
Effect of dilutive securities:
Total (in shares)	[1]		115
Share-based Payment Arrangement [Member]
Effect of dilutive securities:
Total (in shares)		1	11
Series A Convertible Preferred Stock [Member]
Effect of dilutive securities:
Effect of dilutive securities (in shares)	[1]	115

[1] For the three months ended March 31, 2020, the Series A preferred stock was anti-dilutive; therefore, it was excluded from the calculation of diluted loss per share.