Note 7 - Accumulated Other Comprehensive Loss - Accumulated Other Comprehensive Loss Reported in the Consolidated Balance Sheets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Balance	$ 315,513	$ 307,878	$ 293,132
Balance	329,976	315,513	307,878
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Balance	(5,044)	(8,155)	(8,243)
Reclassification adjustments	0	0	0
Current period benefit (charge)	(2,807)	3,111	88
Income tax charge (benefit)	0	0	0
Balance	(7,851)	(5,044)	(8,155)
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Balance	(25,333)	(20,382)	(15,180)
Reclassification adjustments	4,788	7,049	1,753
Current period benefit (charge)	(1,045)	(13,510)	(8,521)
Income tax charge (benefit)	(889)	1,510	1,566
Balance	(22,479)	(25,333)	(20,382)
AOCI Attributable to Parent [Member]
Balance	(30,377)	(28,537)	(23,423)
Reclassification adjustments	4,788	7,049	1,753
Current period benefit (charge)	(3,852)	(10,399)	(8,433)
Income tax charge (benefit)	(889)	1,510	1,566
Balance	$ (30,330)	$ (30,377)	$ (28,537)