Note 3 - Earnings Per Share - Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ 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		$ 10,556	$ 7,068	$ 13,923	$ 11,412	$ 17,624	$ 25,335
Divided by:
Weighted average common shares outstanding (in shares)		28,761,000		28,845,000		28,691,000	28,909,000
Weighted average common stock equivalents (in shares)		0		1,000		0	1,000
Total weighted average common shares outstanding and common stock equivalents (in shares)		28,761,000		28,846,000		28,691,000	28,910,000
Basic earnings per common share (in dollars per share)		$ 0.37		$ 0.48		$ 0.61	$ 0.88
Diluted earnings per common share (in dollars per share)	[1]	$ 0.37		$ 0.48		$ 0.61	$ 0.88
Dividend payout ratio		56.80%		41.70%		68.90%	45.50%

[1] For the three and six months ended June 30, 2019 and 2018, there were no common stock equivalents that were anti-dilutive.