Note 9 - Basic and Diluted Earnings Per Common Share - Reconciliation of Net Income and Number of Shares Used in Computations of Basic and Diluted EPS (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Net income	$ 959,000	$ 804,000	$ 1,467,000	$ 1,354,000
Shares (denominator):
Basic weighted average common shares outstanding (in shares)	14,086,277	14,953,217	14,151,734	15,079,733
Add: dilutive effect of common stock options (in shares)	41,657	52,872	67,329	71,299
Diluted weighted average common shares outstanding (in shares)	14,127,934	15,006,089	14,219,063	15,151,032
Earnings per common share:
Basic (in dollars per share)	$ 0.07	$ 0.05	$ 0.10	$ 0.09
Diluted (in dollars per share)	$ 0.07	$ 0.05	$ 0.10	$ 0.09