Note 15 - Quarterly Financial Data (Unaudited) - Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Total net sales	$ 39,503	$ 38,368	$ 40,670	$ 35,883	$ 37,548	$ 36,416	$ 24,851	$ 30,551	$ 154,424	$ 129,366	$ 117,232
Gross profit	25,956	24,866	26,761	23,799	24,402	22,704	17,029	20,483	101,382	84,618	79,853
Income from operations	8,301	9,073	11,106	7,945	9,545	10,018	4,872	4,353	36,425	28,788	21,183
Net income	$ 6,175	$ 6,504	$ 8,299	$ 5,929	$ 7,033	$ 7,513	$ 3,500	$ 3,174	$ 26,907	$ 21,220	$ 17,934
Basic:
Basic (in dollars per share)	$ 0.28	$ 0.30	$ 0.40	$ 0.29	$ 0.35	$ 0.37	$ 0.17	$ 0.16	$ 1.27	$ 1.05	$ 0.91
Diluted (in dollars per share)	$ 0.28	$ 0.30	$ 0.40	$ 0.28	$ 0.34	$ 0.37	$ 0.17	$ 0.16	$ 1.25	$ 1.04	$ 0.88
Total net sales	$ 39,503	$ 38,368	$ 40,670	$ 35,883	$ 37,548	$ 36,416	$ 24,851	$ 30,551	$ 154,424	$ 129,366	$ 117,232
Gross profit	25,956	24,866	26,761	23,799	24,402	22,704	17,029	20,483	101,382	84,618	79,853
Income from operations	8,301	9,073	11,106	7,945	9,545	10,018	4,872	4,353	36,425	28,788	21,183
Net income	$ 6,175	$ 6,504	$ 8,299	$ 5,929	$ 7,033	$ 7,513	$ 3,500	$ 3,174	$ 26,907	$ 21,220	$ 17,934