Note 4 - Employee Benefit Plans - Net Periodic Pension Cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Defined Benefit Plan, Service Cost	$ 949	$ 1,566	$ 2,847	$ 4,697
Defined Benefit Plan, Interest Cost	1,993	1,369	5,979	4,107
Expected return on plan assets	(3,107)	(3,363)	(9,321)	(10,089)
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	125	128	375	384
Amortization of net loss	(47)	512	(141)	1,537
Net periodic pension cost	$ (87)	$ 212	$ (261)	$ 636