Note 9 - Accumulated Other Comprehensive Loss - Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Balance beginning of period			$ 379,833
Balance at end of period	$ 429,839		429,839
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Balance beginning of period	(7,404)	$ (6,612)	(10,753)	$ (5,212)
Other comprehensive income (loss) before reclassifications	1,655	(154)	5,004	(1,554)
Amounts reclassified from accumulated other comprehensive loss	0	0	0	0
Net current-period other comprehensive income (loss)	1,655	(154)	5,004	(1,554)
Balance at end of period	$ (5,749)	$ (6,766)	$ (5,749)	$ (6,766)