Note 5 - Earnings Per Share - Earnings Per Share Calculation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Net income available to common shareholders	$ 23,107	$ 37,104
Denominator for basic earnings per share – weighted average shares outstanding (in shares)	36,485	36,817
Employee and director stock options and restricted share awards (in shares)	841	1,017
Denominator for diluted earnings per share – adjusted weighted average shares outstanding and assumed conversions (in shares)	37,326	37,834
Basic earnings per common share (in dollars per share)	$ 0.63	$ 1.01
Diluted earnings per common share and common share equivalents (in dollars per share)	$ 0.62	$ 0.98