Note 6 - Net Income Per Common Share - Net Income Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Net income, basic and diluted	$ 5,847	$ 4,482	$ 11,488	$ 7,811
Average common shares issued and outstanding, basic and diluted (in shares)	7,520	7,512	7,519	7,511
Net income per common share, basic and diluted (in dollars per share)	$ 0.78	$ 0.60	$ 1.53	$ 1.04