Note 8 - Product Warranty Obligations - Reconciliation of Product Warranty Liability (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Balance at beginning of period	$ 31,695	$ 30,197
Product warranty reserve assumed in acquisition	43	840
Payments	(4,560)	(3,652)
Provision for warranty issued	4,160	3,482
Changes in estimates for pre-existing warranties	670	1,037
Balance at end of period	32,008	31,904
Balance at beginning of period	31,080	28,961
Deferred revenue contracts issued	1,969	1,144
Amortization of deferred revenue contracts	(1,598)	(1,275)
Balance at end of period	$ 31,451	$ 28,830