Note 4 - Earnings Per Share - Earnings Per Share Calculation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Numerator for basic and diluted earnings per share – Net income available to common shareholders	$ 37,104	$ 21,039
Denominator for basic earnings per share – weighted average shares outstanding (in shares)	36,817	39,665
Effect of dilutive securities– Employee and director stock options and restricted share awards (in shares)	1,017	1,427
Denominator for diluted earnings per share – adjusted weighted average shares outstanding and assumed conversions (in shares)	37,834	41,092
Basic earnings per common share (in dollars per share)	$ 1.01	$ 0.53
Diluted earnings per common share and common share equivalents (in dollars per share)	$ 0.98	$ 0.51