Note 4 - Net Income Per Common Share - Reconciliation of Income (Loss) Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Weighted average number of common shares outstanding - basic (in shares)	3,388,624	3,346,689	3,388,624	3,346,689
Effect of dilutive securities (in shares)	66,312	98,943	49,762	98,943
Weighted average number of common shares and potential common shares - diluted (in shares)	3,454,936	3,445,632	3,438,386	3,445,632
Net income	$ 2,326	$ 1,589	$ 7,230	$ 4,733
Net income per common share - basic (in dollars per share)	$ 0.69	$ 0.47	$ 2.13	$ 1.41
Net income per common share - diluted (in dollars per share)	$ 0.67	$ 0.46	$ 2.10	$ 1.37