Note 8 - Fair Value Measurements (Details Textual) - Foreign Exchange Contract [Member] - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Derivative Asset, Notional Amount	$ 8,100,000		$ 8,100,000		$ 8,200,000
Other Current Assets [Member]
Derivative Asset, Current	35,000		35,000		$ 12,000
Other Nonoperating Income (Expense) [Member]
Derivative, Gain (Loss) on Derivative, Net, Total	$ (600,000)	$ 400,000	$ (400,000)	$ 500,000