Note 8 - Accrued Retirement Benefits - Net Periodic Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Interest cost	$ 408	$ 527	$ 816	$ 1,053
Expected return on plan assets	(497)	(482)	(994)	(967)
Amortization of net loss	206	211	412	423
Pension and other postretirement expenses	$ 117	$ 256	$ 234	$ 509