Note 4 - Earnings Per Share - Earnings Per Share Calculation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Numerator for basic and diluted earnings per share – Net income available to common shareholders	$ 29,784	$ 14,880	$ 66,262	$ 28,092
Denominator for basic earnings per share – weighted average shares outstanding (in shares)	39,825	39,617	39,560	40,138
Effect of dilutive securities– Employee and director stock options and restricted share awards (in shares)	1,321	657	1,270	560
Denominator for diluted earnings per share – adjusted weighted average shares outstanding and assumed conversions (in shares)	41,146	40,274	40,830	40,698
Basic earnings per common share (in dollars per share)	$ 0.75	$ 0.38	$ 1.68	$ 0.70
Diluted earnings per common share and common share equivalents (in dollars per share)	$ 0.72	$ 0.37	$ 1.62	$ 0.69