Note 5 - Derivative Instruments and Hedging Activities - Effects of Derivative Instruments on Income and Other Comprehensive Income (OCI) (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017		Sep. 30, 2018	Sep. 30, 2017
Amount of Gain or (Loss) Recognized in OCI, Net of Tax, on Derivative (Effective Portion)	$ 144	$ 309	[1]	$ (112)	$ 638	[1]
Amount of Gain or (Loss) Recognized in OCI, Net of Tax, on Derivative (Effective Portion)	144	309	[1]	(112)	638	[1]
Operating Expense [Member]
Amount of Gain or (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	(71)	432		(87)	561
Amount of Gain or (Loss) Recognized in Income on Derivative (Ineffective Portion and Amount Excluded from Effectiveness Testing)
Amount of Gain or (Loss) Recognized in OCI, Net of Tax, on Derivative (Effective Portion)				(36)	222
Amount of Gain or (Loss) Recognized in OCI, Net of Tax, on Derivative (Effective Portion)				(36)	222
Cost of Sales [Member]
Amount of Gain or (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	(12)	66		$ (13)	$ 91
Amount of Gain or (Loss) Recognized in Income on Derivative (Ineffective Portion and Amount Excluded from Effectiveness Testing)
Amount of Gain or (Loss) Recognized in OCI, Net of Tax, on Derivative (Effective Portion)	207	(9)
Amount of Gain or (Loss) Recognized in OCI, Net of Tax, on Derivative (Effective Portion)	$ 207	$ (9)

[1] The Company has initially applied ASC 2014-09 (Topic 606) using the modified retrospective method. Under this method, the comparative information is not restated.