Note 2 - Summary of Significant Accounting Policies - Reconciliation of Net Income and Number of Shares Used in Computations of Basic and Diluted EPS (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Net income	$ 2,633,000	$ 3,168,000
Shares (denominator):
Basic weighted average common shares outstanding (in shares)	14,825,600	16,835,129
Add: Dilutive effect of common stock options (in shares)	167,409
Diluted weighted average common shares outstanding (in shares)	14,993,009	16,835,129
Earnings per common share:
Basic earnings per common share (in dollars per share)	$ 0.18	$ 0.19
Diluted earnings per common share (in dollars per share)	$ 0.18	$ 0.19