Note 7 - Earnings Per Share - Reconciliation of Basic and Diluted Earnings Per Share (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Net earnings used in the computation of basic and diluted earnings per share	$ 4,962,000	$ 4,447,000	$ 13,138,000	$ 10,197,000
Weighted average shares outstanding - basic (in shares)	14,573,813	14,118,354	14,475,311	14,055,345
Common stock equivalents (in shares)	655,909	865,730	591,305	814,726
Weighted average shares outstanding - diluted (in shares)	15,229,722	14,984,084	15,066,616	14,870,071
Weighted average number of shares outstanding during the period
Net earnings (in dollars per share)	$ 0.34	$ 0.31	$ 0.91	$ 0.73
Net earnings (in dollars per share)	$ 0.33	$ 0.30	$ 0.87	$ 0.69