Note 4 - Earnings Per Share - Earnings Per Share Calculation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Numerator for basic and diluted earnings per share – Net income available to common shareholders	$ 21,999	$ 10,817	$ 36,478	$ 13,212
Denominator for basic earnings per share – weighted average shares outstanding (in shares)	39,641	40,250	39,493	40,402
Effect of dilutive securities– Employee stock options and restricted stock awards (in shares)	1,198	528	1,244	512
Denominator for diluted earnings per share – adjusted weighted average shares outstanding and assumed conversions (in shares)	40,839	40,778	40,737	40,914
Basic earnings per common share (in dollars per share)	$ 0.55	$ 0.27	$ 0.92	$ 0.33
Diluted earnings per common share and common share equivalents (in dollars per share)	$ 0.54	$ 0.27	$ 0.90	$ 0.32