Note 11 - Product Warranty Obligations - Reconciliation of Product Warranty Liability (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Balance at beginning of period	$ 41,785	$ 35,422	$ 31,695
Product warranty reserve assumed in acquisition	1,062	0	43
Payments	(26,096)	(20,029)	(18,861)
Provision for warranty issued	32,060	26,910	21,347
Changes in estimates for pre-existing warranties	505	(518)	1,198
Balance at end of period	49,316	41,785	35,422
Balance at beginning of period	68,340	57,854	36,139
Deferred revenue contracts issued	24,483	21,440	29,262
Amortization of deferred revenue contracts	(14,085)	(10,954)	(7,547)
Balance at end of period	$ 78,738	$ 68,340	$ 57,854