Note 7 - Accumulated Other Comprehensive Loss - Disclosure of Changes in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended				9 Months Ended
	Sep. 30, 2018		Sep. 30, 2017		Sep. 30, 2018		Sep. 30, 2017
Beginning Balance					$ 554,319
Ending Balance	$ 698,635				698,635
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Beginning Balance	(17,335)		$ (15,857)		(12,856)		$ (28,047)
Other comprehensive income (loss) before reclassifications	5,717		3,826		1,238		16,016
Amounts reclassified from AOCL
Other comprehensive income (loss)	5,717		3,826		1,238		16,016
Ending Balance	(11,618)		(12,031)		(11,618)		(12,031)
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Beginning Balance	(10,978)		(11,040)		(10,978)		(11,040)
Other comprehensive income (loss) before reclassifications
Amounts reclassified from AOCL
Other comprehensive income (loss)
Ending Balance	(10,978)		(11,040)		(10,978)		(11,040)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Beginning Balance	11,413		(312)		2,636		(1,076)
Other comprehensive income (loss) before reclassifications	1,626	[1]	581	[2]	10,403	[3]	1,345	[4]
Amounts reclassified from AOCL
Other comprehensive income (loss)	1,626		581		10,403		1,345
Ending Balance	13,039		269		13,039		269
AOCI Attributable to Parent [Member]
Beginning Balance	(16,900)		(27,209)		(21,198)		(40,163)
Other comprehensive income (loss) before reclassifications	7,343		4,407		11,641		17,361
Amounts reclassified from AOCL
Other comprehensive income (loss)	7,343		4,407		11,641		17,361
Ending Balance	$ (9,557)		$ (22,802)		$ (9,557)		$ (22,802)

[1] Represents unrealized gains of $2,197, net of tax effect of $(571), for the three months ended September 30, 2018.

[2] Represents unrealized gains of $954, net of tax effect of $(373), for the three months ended September 30, 2017.

[3] Represents unrealized gains of $14,057, net of tax effect of $(3,654), for the nine months ended September 30, 2018.

[4] Represents unrealized gains of $2,208, net of tax effect of $(863), for the nine months ended September 30, 2017.