Note 9 - Quarterly Results for 2016, 2017 and 2018 (Unaudited) - Quarterly Results (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net sales	$ 95,001	$ 95,870	$ 82,392	$ 73,087	$ 72,450	$ 67,773	$ 65,604	$ 60,987	$ 64,686	$ 65,282	$ 64,660	$ 57,968	$ 346,350	$ 266,814	$ 252,596
Gross profit	33,744	33,800	29,278	24,875	25,975	24,789	23,374	22,214	22,058	23,140	21,763	20,021	121,697	96,352	86,982
Income before taxes on income	5,696	7,282	5,097	3,320	6,834	6,842	5,701	5,405	5,867	6,006	4,615	3,410
Net earnings used in the computation of basic and diluted earnings per share (in thousands)	$ 4,586	$ 6,122	$ 3,817	$ 2,450	$ 1,884	$ 4,962	$ 4,341	$ 3,835	$ 4,441	$ 4,447	$ 3,308	$ 2,442	$ 16,975	$ 15,022	$ 14,638
Weighted average number of shares outstanding during the period
Net earnings (in dollars per share)	$ 0.31	$ 0.41	$ 0.26	$ 0.17	$ 0.12	$ 0.33	$ 0.29	$ 0.26	$ 0.31	$ 0.31	$ 0.23	$ 0.18	$ 1.14	$ 1.04	$ 1.04
Net earnings (in dollars per share)	$ 0.30	$ 0.39	$ 0.25	$ 0.16	$ 0.13	$ 0.34	$ 0.30	$ 0.27	$ 0.30	$ 0.30	$ 0.22	$ 0.17	$ 1.10	$ 0.99	$ 0.98
(Basic) (in shares)	14,962,603	15,010,660	14,956,221	14,821,659	14,614,691	14,573,813	14,501,399	14,350,721	14,162,939	14,118,354	14,120,617	13,927,063	14,937,786	14,510,156	14,082,243
(Diluted) (in shares)	15,371,606	15,449,894	15,990,404	15,457,629	15,275,222	15,229,722	15,040,431	14,929,695	14,979,746	14,984,084	14,957,469	14,668,658	15,472,133	15,118,768	14,897,489
Net sales	$ 95,001	$ 95,870	$ 82,392	$ 73,087	$ 72,450	$ 67,773	$ 65,604	$ 60,987	$ 64,686	$ 65,282	$ 64,660	$ 57,968	$ 346,350	$ 266,814	$ 252,596
Gross profit	33,744	33,800	29,278	24,875	25,975	24,789	23,374	22,214	22,058	23,140	21,763	20,021	121,697	96,352	86,982
Income before taxes on income	5,696	7,282	5,097	3,320	6,834	6,842	5,701	5,405	5,867	6,006	4,615	3,410
Net earnings used in the computation of basic and diluted earnings per share (in thousands)	$ 4,586	$ 6,122	$ 3,817	$ 2,450	$ 1,884	$ 4,962	$ 4,341	$ 3,835	$ 4,441	$ 4,447	$ 3,308	$ 2,442	$ 16,975	$ 15,022	$ 14,638