Note 13 - Earnings Per Share - Reconciliation of Basic and Diluted Earnings Per Share (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 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 shares outstanding - 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
Common stock equivalents (in shares)													534,347	608,612	815,246
(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
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