Note 4 - Employee Benefit Plans - Net Periodic Pension Cost (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Defined Benefit Plan, Service Cost	$ 949	$ 1,566
Defined Benefit Plan, Interest Cost	1,993	1,369
Expected return on plan assets	(3,107)	(3,363)
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	125	128
Amortization of net loss	47	512
Net periodic pension cost	$ 87	$ 212