Note 15 - Accumulated Other Comprehensive Loss - Changes in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Balance	$ 405,427	$ 310,835
Balance	544,864	405,427
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Balance	(34,290)	(25,880)
Other comprehensive income/(loss) before reclassifications	22,250	(8,481)
Amounts reclassified from accumulated other comprehensive loss		71
Net current-period other comprehensive income/(loss)	22,250	(8,410)
Balance	(12,040)	(34,290)
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Balance	(31,230)	(29,569)
Other comprehensive income/(loss) before reclassifications	121	(2,468)
Amounts reclassified from accumulated other comprehensive loss	921	807
Net current-period other comprehensive income/(loss)	1,042	(1,661)
Balance	(30,188)	(31,230)
AOCI Attributable to Parent [Member]
Balance	(65,520)	(55,449)
Other comprehensive income/(loss) before reclassifications	22,371	(10,949)
Amounts reclassified from accumulated other comprehensive loss	921	878
Net current-period other comprehensive income/(loss)	23,292	(10,071)
Balance	$ (42,228)	$ (65,520)