Note 6 - Accrued Retirement Benefits - Net Periodic Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Pension and other benefits:
Interest cost	$ 2,096	$ 1,974
Expected return on plan assets	(1,965)	(2,319)
Recognized net actuarial loss	865	786
Pension expense	996	441
Other changes in plan assets and benefit obligations recognized in comprehensive income:
Net (gain) loss	(141)	2,314
Recognized gain	(865)	(764)
Total recognized (gain) loss in comprehensive income	$ (1,006)	$ 1,550