Note 8 - Accrued Retirement Benefits - Net Periodic Cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Interest cost	$ 560	$ 803	$ 1,680	$ 2,182
Expected return on plan assets	(562)	(659)	(1,686)	(1,977)
Amortization of net loss	204	253	612	760
Recognized gain due to settlements		(654)		(654)
Pension and other postretirement expenses (income)	202	(257)	606	311
Net loss	204	253	612	760
Recognized actuarial loss due to settlement		721		721
Total recognized loss in comprehensive income	$ 204	$ 974	$ 612	$ 1,481