Note 8 - Accrued Retirement Benefits - Net Periodic Cost (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Interest cost	$ 408	$ 527
Expected return on plan assets	(497)	(485)
Amortization of net loss	206	211
Pension and other postretirement expenses	$ 117	$ 253