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, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Numerator for basic and diluted earnings per share –Net income available to common shareholders	$ 90,376	$ 69,399	$ 293,056	$ 172,776
Basic (in shares)	55,232	56,007	55,601	55,882
Effect of dilutive securities– Employee and director stock options and restricted share awards (in shares)	1,643	1,799	1,762	1,952
Denominator for diluted earnings per share – adjusted weighted average shares outstanding and assumed conversions (in shares)	56,875	57,806	57,363	57,834
Basic earnings per common share (in dollars per share)	$ 1.64	$ 1.24	$ 5.27	$ 3.09
Diluted earnings per common share and common share equivalents (in dollars per share)	$ 1.59	$ 1.20	$ 5.11	$ 2.99