Note 1 - Summary of Significant Accounting Policies - Impact of New Standard on Statement of Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Net sales	$ 86,552	$ 73,087
Cost of goods sold	56,284	48,212
Selling and administrative expenses	25,863	21,182
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Net sales	88,346
Cost of goods sold	57,117
Selling and administrative expenses	25,822
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
Net sales	(1,794)	$ 3,800
Cost of goods sold	(833)
Selling and administrative expenses	$ 41