Note 8 - Accrued Retirement Benefits - Net Periodic Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Interest cost	$ 309	$ 408	$ 618	$ 816
Expected return on plan assets	(418)	(497)	(836)	(994)
Amortization of net loss	221	206	442	412
Pension and other postretirement expenses	$ 112	$ 117	$ 224	$ 234