Note 6 - Accrued Retirement Benefits - Net Periodic Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Pension and other benefits:
Interest cost	$ 1,633	$ 2,096
Expected return on plan assets	(2,020)	(1,965)
Recognized net actuarial loss	839	865
Pension expense	452	996
Other changes in plan assets and benefit obligations recognized in comprehensive income:
Net loss (gain)	1,739	(141)
Amortization of recognized gain	(839)	(865)
Total recognized loss (gain) in comprehensive loss	$ 900	$ (1,006)