Note 9 - Quarterly Results for 2014, 2015 and 2016 (Unaudited) - Quarterly Results (Details) - USD ($)	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, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net sales	$ 64,686,000	$ 65,282,000	$ 64,660,000	$ 57,968,000	$ 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	22,058,000	23,140,000	21,763,000	20,021,000	17,882,000	19,224,000	18,531,000	15,796,000	17,242,000	18,433,000	19,006,000	14,056,000	$ 86,982,000	$ 71,433,000	$ 68,737,000
Income before taxes on income	5,867,000	6,006,000	4,615,000	3,410,000	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	$ 4,441,000	$ 4,447,000	$ 3,308,000	$ 2,442,000	$ 3,368,000	$ 4,031,000	$ 3,624,000	$ 2,043,000	$ 2,856,000	$ 3,368,000	$ 3,907,000	$ 1,218,000	$ 14,638,000	$ 13,066,000	$ 11,349,000
Weighted average number of shares outstanding during the period
Net income (in dollars per share)	$ 0.31	$ 0.31	$ 0.23	$ 0.18	$ 0.24	$ 0.29	$ 0.26	$ 0.15	$ 0.21	$ 0.25	$ 0.30	$ 0.09	$ 1.04	$ 0.95	$ 0.85
Net income (in dollars per share)	$ 0.30	$ 0.30	$ 0.22	$ 0.17	$ 0.23	$ 0.28	$ 0.25	$ 0.14	$ 0.20	$ 0.24	$ 0.29	$ 0.09	$ 0.98	$ 0.90	$ 0.82
(Basic) (in shares)	14,162,939	14,118,354	14,120,617	13,927,063	13,894,907	13,833,561	13,730,646	13,584,922	13,481,494	13,375,566	13,207,804	13,128,946	14,082,243	13,761,009	13,298,452
(Diluted) (in shares)	14,979,746	14,984,084	14,957,469	14,668,658	14,603,464	14,585,688	14,577,342	14,548,084	14,252,310	14,004,202	13,648,540	13,553,740	14,897,489	14,578,644	13,864,698
Net sales	$ 64,686,000	$ 65,282,000	$ 64,660,000	$ 57,968,000	$ 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	22,058,000	23,140,000	21,763,000	20,021,000	17,882,000	19,224,000	18,531,000	15,796,000	17,242,000	18,433,000	19,006,000	14,056,000	$ 86,982,000	$ 71,433,000	$ 68,737,000
Income before taxes on income	5,867,000	6,006,000	4,615,000	3,410,000	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	$ 4,441,000	$ 4,447,000	$ 3,308,000	$ 2,442,000	$ 3,368,000	$ 4,031,000	$ 3,624,000	$ 2,043,000	$ 2,856,000	$ 3,368,000	$ 3,907,000	$ 1,218,000	$ 14,638,000	$ 13,066,000	$ 11,349,000