Note 6 - Earnings per Common Share - Basic and Diluted Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Numerator:
Net income	$ 110,354	$ 85,428	$ 69,500
Denominator:
Basic earnings per common share - weighted-average shares (in shares)	81,692	82,872	82,527
Effect of dilutive stock options (in shares)	267	536	637
Diluted earnings per common share - weighted-average shares and assumed conversions (in shares)	81,959	83,408	83,164
Basic earnings per common share (in dollars per share)	$ 1.35	$ 1.03	$ 0.84
Diluted earnings per common share (in dollars per share)	$ 1.35	$ 1.02	$ 0.84