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
	Mar. 31, 2019	Mar. 31, 2018
Net income	$ 1,218,000	$ 508,000
Shares (denominator):
Basic weighted average common shares outstanding (in shares)	13,391,992	14,217,919
Add: dilutive effect of common stock options (in shares)	77,505	165,086
Diluted weighted average common shares outstanding (in shares)	13,469,497	14,383,005
Earnings per common share:
Basic (in dollars per share)	$ 0.09	$ 0.04
Diluted (in dollars per share)	$ 0.09	$ 0.04