Note 4 - Employee Benefit Plans - Net Periodic Pension Cost (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Service cost	$ 1,566	$ 1,455
Interest cost	1,369	1,248
Expected return on plan assets	(3,363)	(2,313)
Amortization of prior service cost	128	99
Amortization of net loss	512	1,125
Net periodic pension cost	$ 212	$ 1,614