Note 12 - Earnings Per Share - Earnings Per Share Calculation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net income available to common shareholders	$ 172,129	$ 40,582	$ 66,053
Denominator for basic earnings per share – weighted average shares outstanding (in shares)	39,627	39,938	40,271
Employee and director stock options and restricted share awards (in shares)	1,353	665	822
Denominator for diluted earnings per share - adjusted weighted average shares outstanding and assumed conversions (in shares)	40,980	40,603	41,093
Basic earnings per common share (in dollars per share)	$ 4.34	$ 1.02	$ 1.64
Diluted earnings per common share and common share equivalents (in dollars per share)	$ 4.20	$ 1	$ 1.96