Note 5 - Net Income Per Common Share - Net Income Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Net income, basic and diluted	$ 5,312	$ 4,324	$ 13,123	$ 14,060
Average common shares issued and outstanding, basic and diluted (in shares)	7,514	7,505	7,512	7,503
Net income per common share, basic and diluted (in dollars per share)	$ 0.71	$ 0.58	$ 1.75	$ 1.87