Note 11 - Retirement Plans - Summary of Funded Status and Amounts Recognized on Balance Sheets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Projected benefit obligation at beginning of year	$ 135	$ 117
Interest cost	4	5	$ 5
Actuarial loss	16	17
Benefits paid	(4)	(4)
Projected benefit obligation at end of year	151	135	117
Fair value of pension plan assets at beginning of year	97	84
Actual return on plan assets	12	14
Company contributions	3	3
Benefits paid	(4)	(4)
Fair value of pension plan assets at end of year	108	97	$ 84
Funded status of pension plan	(43)	(38)
Accrued benefit cost	10	5
Accumulated other comprehensive loss	(53)	(43)
Net liability recognized	$ (43)	$ (38)