Note 11 - Retirement Plans - Summary of Funded Status and Amounts Recognized on Balance Sheets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Projected benefit obligation at beginning of year	$ 102	$ 140
Interest cost	5	4	$ 4
Actuarial loss (gain)	2	(38)
Benefits paid	(5)	(4)
Projected benefit obligation at end of year	104	102	140
Fair value of pension plan assets at beginning of year	104	119
Actual return (loss) on plan assets	14	(14)
Company contributions	4	4
Benefits paid	(5)	(5)
Fair value of pension plan assets at end of year	117	104	$ 119
Funded status of pension plan	13	2
Accrued benefit cost	26	21
Accumulated other comprehensive loss	(13)	(19)
Net asset (liability) recognized	$ 13	$ 2