Note 18 - Quarterly Financial Information (Unaudited) - Summarized Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net sales	$ 36,507	$ 37,220	$ 37,902	$ 34,503	$ 33,933	$ 34,441	$ 36,499	$ 33,977	$ 146,132	$ 138,850	$ 139,307
Gross profit	8,176	8,452	10,295	7,727	9,013	9,510	10,293	8,638	$ 34,650	$ 37,454	$ 36,880
Net income	$ 1,491	$ 2,669	$ 2,735	$ 1,075	$ 1,676	$ 1,992	$ 2,272	$ 1,653
Basic net income per share (in dollars per share)	$ 0.21	$ 0.37	$ 0.38	$ 0.15	$ 0.24	$ 0.28	$ 0.32	$ 0.23	$ 1.11	$ 1.07	$ 1.08
Diluted net income per share (in dollars per share)	$ 0.20	$ 0.37	$ 0.38	$ 0.15	$ 0.23	$ 0.28	$ 0.32	$ 0.23	$ 1.10	$ 1.05	$ 1.05