Note 8 - Accrued Retirement Benefits - Net Periodic Cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Interest cost	$ 309	$ 408	$ 927	$ 1,225
Expected return on plan assets	(418)	(489)	(1,254)	(1,483)
Amortization of net loss	225	206	675	617
Pension and other postretirement expenses	$ 116	$ 125	$ 348	$ 359