Note 11 - Earnings Per Common Share - Earnings Per Common Share and Diluted Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Net income (numerator)	$ 17,506	$ 15,049
Basic earnings per common share
Weighted average number of common shares outstanding - basic (in shares)	26,532	26,171
Basic earnings per common share (in dollars per share)	$ 0.66	$ 0.58
Diluted earnings per common share
Weighted average number of common shares outstanding - basic (in shares)	26,532	26,171
Add common stock equivalents for options (in shares)	133	158
Weighted average number of common shares outstanding - diluted (denominator) (in shares)	26,665	26,329
Diluted earnings per common share (in dollars per share)	$ 0.66	$ 0.57