Note 7 - Earnings Per Share - Calculation of Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Net income	$ 3,818	$ 3,280
Basic earnings per common share (in dollars per share)	$ 0.74	$ 0.65
Diluted earnings per common share (in dollars per share)	$ 0.73	$ 0.63
Basic shares (in shares)	5,144	5,071
Diluted shares (in shares)	5,225	5,208