Note 1 - Summary of Significant Interim Accounting Policies - Impact of New Standard on Statement of Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Net sales	$ 95,870	$ 67,773	$ 251,349	$ 194,365
Cost of goods sold	62,070	42,984	163,396	123,987
Selling and administrative expenses	25,482	$ 17,386	69,991	$ 51,809
Accounting Standards Update 2014-09 [Member]
Net sales			42,880
Cost of goods sold			27,397
Selling and administrative expenses			706
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Net sales	92,945		247,634
Cost of goods sold	59,908		160,551
Selling and administrative expenses	25,527		70,058
Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Net sales	2,925		3,715
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
Net sales	2,925		3,715
Cost of goods sold	2,162		2,845
Selling and administrative expenses	$ (45)		$ (67)