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						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Net income	$ 437,000	$ 1,010,000	$ 1,218,000	$ 1,539,000	$ 959,000	$ 508,000	$ 2,665,000	$ 3,007,000
Shares (denominator):
Basic weighted average common shares outstanding (in shares)	13,056,173			13,795,007			13,209,598	14,031,518
Add: dilutive effect of common stock options (in shares)	19,519			58,612			28,428	44,515
Diluted weighted average common shares outstanding (in shares)	13,075,692			13,853,619			13,238,026	14,076,033
Earnings per common share:
Basic (in dollars per share)	$ 0.03			$ 0.11			$ 0.20	$ 0.21
Diluted (in dollars per share)	$ 0.03			$ 0.11			$ 0.20	$ 0.21