Note 8 - Accrued Retirement Benefits - Net Periodic Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Interest cost	$ 527	$ 495	$ 1,053	$ 990
Expected return on plan assets	(482)	(578)	(967)	(1,156)
Amortization of net loss	211	185	423	370
Pension and other postretirement expenses	$ 256	$ 102	$ 509	$ 204