Note 10 - Accumulated Other Comprehensive Loss - Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Balance	$ 558,113	$ 506,253	$ 541,497	$ 461,215
Balance	564,097	531,206	564,097	531,206
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Balance	(8,494)	(6,359)	(8,492)	(5,234)
Other comprehensive income (loss) before reclassifications	(2,150)	(879)	(2,152)	(2,004)
Amounts reclassified from accumulated other comprehensive loss	0	0	0	0
Net current-period other comprehensive income (loss)	(2,150)	(879)	(2,152)	(2,004)
Balance	$ (10,644)	$ (7,238)	$ (10,644)	$ (7,238)