Note 6 - Warranty and Service Contracts - Summary of Warranties (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Beginning Balance	$ 3,373	$ 2,735	$ 3,508	$ 2,461
Add: Accruals for warranties issued during the period	2,311	1,944	4,575	4,079
Less: Settlements made during the period	(2,123)	(1,802)	(4,522)	(3,663)
Ending Balance	$ 3,561	$ 2,877	$ 3,561	$ 2,877