Note 11 - Warranty Accrual - Warranty Accrual and Payment Activity (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Balance at beginning of period	$ 21,909	$ 20,678
Expense provisions	2,598	2,407
Cash payments	(2,500)	(2,365)
Adjustments	3,106	50
Balance at end of period	$ 25,113	$ 20,770