Note 10 - Income Taxes - Activity in Uncertain Tax Positions (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Balance at beginning of period	$ 15	$ 15	$ 14
Additions based on tax positions related to prior years	0	0	3
Statute expirations	(1)	0	(2)
Balance at end of period	$ 14	$ 15	$ 15