Note 11 - Accumulated Other Comprehensive Income/(Loss) - Schedule of Changes in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance			$ 544,864
Ending balance	$ 659,278		659,278
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	(22,576)	$ (21,543)	(12,040)	$ (34,290)
Other comprehensive income/(loss) before reclassifications	32	7,006	(10,504)	19,753
Net current-period other comprehensive (loss)/income	32	7,006	(10,504)	19,753
Ending balance	(22,544)	(14,537)	(22,544)	(14,537)
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	(29,687)	(30,743)	(30,188)	(31,230)
Amounts reclassified from accumulated other comprehensive loss	202	250	703	737
Net current-period other comprehensive (loss)/income	202	250	703	737
Ending balance	(29,485)	(30,493)	(29,485)	(30,493)
AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	(52,263)	(52,286)	(42,228)	(65,520)
Other comprehensive income/(loss) before reclassifications	32	7,006	(10,504)	19,753
Amounts reclassified from accumulated other comprehensive loss	202	250	703	737
Net current-period other comprehensive (loss)/income	234	7,256	(9,801)	20,490
Ending balance	$ (52,029)	$ (45,030)	$ (52,029)	$ (45,030)