Note 9 - Quarterly Results (Details) - USD ($)	3 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014
Net sales	$ 53,192,000	$ 56,662,000	$ 54,116,000	$ 46,347,000	$ 49,701,000	$ 52,291,000	$ 53,230,000	$ 41,027,000
Gross profit	17,882,000	19,224,000	18,531,000	15,796,000	17,242,000	18,433,000	19,006,000	14,056,000
Income before taxes on income	4,698,000	5,581,000	5,394,000	3,223,000	4,616,000	5,168,000	5,867,000	1,878,000
Net income	$ 3,368,000	$ 4,031,000	$ 3,624,000	$ 2,043,000	$ 2,856,000	$ 3,368,000	$ 3,907,000	$ 1,218,000
Weighted average number of shares outstanding during the period
Net income (in dollars per share)	$ 0.24	$ 0.29	$ 0.26	$ 0.15	$ 0.21	$ 0.25	$ 0.30	$ 0.09
Net income (in dollars per share)	$ 0.23	$ 0.28	$ 0.25	$ 0.14	$ 0.20	$ 0.24	$ 0.29	$ 0.09
(Basic) (in shares)	13,894,907	13,833,561	13,730,646	13,584,922	13,481,494	13,375,566	13,207,804	13,128,946
(Diluted) (in shares)	14,603,464	14,585,688	14,577,342	14,548,084	14,252,310	14,004,202	13,648,540	13,553,740
Net sales	$ 53,192,000	$ 56,662,000	$ 54,116,000	$ 46,347,000	$ 49,701,000	$ 52,291,000	$ 53,230,000	$ 41,027,000
Gross profit	17,882,000	19,224,000	18,531,000	15,796,000	17,242,000	18,433,000	19,006,000	14,056,000
Income before taxes on income	4,698,000	5,581,000	5,394,000	3,223,000	4,616,000	5,168,000	5,867,000	1,878,000
Net income	$ 3,368,000	$ 4,031,000	$ 3,624,000	$ 2,043,000	$ 2,856,000	$ 3,368,000	$ 3,907,000	$ 1,218,000