Note 4 - Employee Benefit Plans - Net Periodic Pension Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Service cost	$ 1,566	$ 1,455	$ 3,131	$ 2,910
Interest cost	1,369	1,248	2,738	2,496
Expected return on plan assets	(3,363)	(2,313)	(6,726)	(4,626)
Amortization of prior service cost	128	99	256	198
Amortization of net loss	512	1,125	1,024	2,250
Net periodic pension cost	$ 212	$ 1,614	$ 423	$ 3,228