Note 3 - Earnings Per Common Share - Summary of Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Weighted average common shares outstanding (in shares)	54,424,561	54,315,671	54,398,845	54,291,739
Net income available to common stockholders	$ 53,340	$ 64,031	$ 164,748	$ 183,749
Basic earnings per common share (in dollars per share)	$ 0.98	$ 1.18	$ 3.03	$ 3.38
Dilutive effects of assumed exercise of stock options and vesting of performance shares (in shares)	106,074	231,011	131,952	242,054
Weighted average common and dilutive potential common shares outstanding (in shares)	54,530,635	54,546,682	54,530,797	54,533,793
Net income available to common stockholders	$ 53,340	$ 64,031	$ 164,748	$ 183,749
Diluted earnings per common share (in dollars per share)	$ 0.98	$ 1.17	$ 3.02	$ 3.37