Note 4 - Employee Benefit Plans - Net Periodic Pension Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Defined Benefit Plan, Service Cost	$ 949	$ 1,566	$ 1,898	$ 3,131
Defined Benefit Plan, Interest Cost	1,993	1,369	3,986	2,738
Expected return on plan assets	(3,107)	(3,363)	(6,214)	(6,726)
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	125	128	250	256
Amortization of net loss	(47)	512	(94)	1,024
Net periodic pension cost	$ (87)	$ 212	$ (174)	$ 423