Note 3 - Earnings Per Share - Earnings 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		$ 13,923	$ 12,725	$ 25,335	$ 24,985
Divided by:
Weighted average common shares outstanding (in shares)		28,845	29,135	28,909	29,077
Weighted average common stock equivalents (in shares)		1	1	1	3
Total weighted average common shares outstanding and common stock equivalents (in shares)		28,846	29,136	28,910	29,080
Basic earnings per common share (in dollars per share)		$ 0.48	$ 0.44	$ 0.88	$ 0.86
Diluted earnings per common share (in dollars per share)	[1]	$ 0.48	$ 0.44	$ 0.88	$ 0.86
Dividend payout ratio		41.70%	40.90%	45.50%	41.90%

[1] For the three and six months ended June 30, 2018 and 2017, there were no common stock equivalents that were anti-dilutive.