Note 8 - Accrued Retirement Benefits - Net Periodic Cost (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Interest cost	$ 309	$ 408
Expected return on plan assets	(414)	(497)
Amortization of net actuarial loss	221	206
Pension and other postretirement expenses	$ 116	$ 117