Note 9 - Non-pension Post-retirement Benefits - Non-pension Post-retirement Benefit Expense (Details) - Non-Pension Post-retirement Benefit Plans [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Service cost (benefits earned during the period)	$ 444	$ 605
Interest cost on projected benefit obligation	1,872	1,860
Prior service cost (credit)	(282)	(282)
Actuarial (gain) loss	(452)	(273)
Non-pension post-retirement benefit expense (income)	1,582	1,910
UNITED STATES
Service cost (benefits earned during the period)	443	604
Interest cost on projected benefit obligation	1,836	1,822
Prior service cost (credit)	(282)	(282)
Actuarial (gain) loss	(376)	(209)
Non-pension post-retirement benefit expense (income)	1,621	1,935
Foreign Plan [Member]
Service cost (benefits earned during the period)	1	1
Interest cost on projected benefit obligation	36	38
Prior service cost (credit)
Actuarial (gain) loss	(76)	(64)
Non-pension post-retirement benefit expense (income)	$ (39)	$ (25)