Note 4 - Earnings Per Share Calculation (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Numerator for basic and diluted earnings per share – Net income available to common shareholders	$ 19,576	$ 19,838	$ 36,357	$ 31,852
Denominator for basic earnings per share – weighted average shares outstanding (in shares)	40,275	39,751	40,171	39,544
Effect of dilutive securities– Employee and director stock options and restricted share awards (in shares)	797	1,098	858	1,138
Denominator for diluted earnings per share – adjusted weighted average shares outstanding and assumed conversions (in shares)	41,072	40,849	41,029	40,682
Basic earnings per common share (in dollars per share)	$ 0.49	$ 0.50	$ 0.91	$ 0.81
Diluted earnings per common share and common share equivalents (in dollars per share)	$ 0.48	$ 0.49	$ 0.89	$ 0.78