Note 2 - Earnings Per Common Share - Basic and Diluted Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016
Net income	$ 9,141	$ 8,531	$ 17,355	$ 16,740	$ 16,724
Basic earnings per common share - weighted-average shares (in shares)	54,493	54,069	54,459		54,079
Effect of dilutive stock options (in shares)	309	320	313		312
Diluted earnings per common share - weighted-average shares and assumed conversions (in shares)	54,802	54,389	54,772		54,391
Basic earnings per common share (in dollars per share)	$ 0.17	$ 0.16	$ 0.32		$ 0.31
Diluted earnings per common share (in dollars per share)	$ 0.17	$ 0.16	$ 0.32		$ 0.31