Note 6 - Earnings Per Common Share - Earnings Per Common 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
Net income		$ 371	$ 427	$ 1,419	$ 260
Less: Series A convertible preferred stock dividend			24	24	73
Less: Excess consideration paid for redemption of preferred shares	[1]			803
Net income available to common shareholders – basic		371	403	592	187
Plus: Series A convertible preferred stock dividend			24
Net income available to common shareholders – diluted		$ 371	$ 427	$ 592	$ 187
Weighted-average common shares outstanding – basic (in shares)		852	760	821	760
Employee stock options and other dilutive securities (in shares)		14	14	16	8
Weighted-average common shares outstanding – diluted (in shares)		866	889	837	768
Basic (Note 6) (in dollars per share)		$ 0.44	$ 0.53	$ 0.72	$ 0.25
Diluted (Note 6) (in dollars per share)		$ 0.43	$ 0.48	$ 0.71	$ 0.24
Total (in shares)		0	3	41	122
Series A Convertible Preferred Stock [Member]
Total (in shares)	[2]			41	115
Share-based Payment Arrangement [Member]
Total (in shares)			3		7
Series A Convertible Preferred Stock [Member]
Series A convertible preferred stock (in shares)	[2]		115

[1] Refer to Note 6 (Earnings per Share) and Note 14 (Shareholders' Equity) to the consolidated financial statements for additional information.

[2] For the nine months ended September 30, 2021 and 2020, the Preferred Stock was anti-dilutive; therefore, it was excluded from the calculation of diluted earnings per share.