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				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Net income applicable to common equity (numerator)	$ 19,625	$ 19,646	$ 18,010	$ 17,506	$ 39,271	$ 35,516
Basic earnings per common share
Weighted average number of common shares outstanding - basic (in shares)	26,942		26,630		26,892	26,581
Basic earnings per common share (in dollars per share)	$ 0.73		$ 0.68		$ 1.46	$ 1.34
Diluted earnings per common share
Weighted average number of common shares outstanding - basic (in shares)	26,942		26,630		26,892	26,581
Add common stock equivalents for options (in shares)	45		98		58	115
Weighted average number of common shares outstanding - diluted (denominator) (in shares)	26,987		26,728		26,950	26,696
Diluted earnings per common share (in dollars per share)	$ 0.73		$ 0.67		$ 1.46	$ 1.33