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, 2021	Dec. 31, 2020	Dec. 31, 2019
Numerator:
Net income	$ 85,428	$ 69,500	$ 61,071
Denominator:
Basic earnings per common share - weighted-average shares (in shares)	82,872	82,527	81,945
Effect of dilutive stock options (in shares)	536	637	725
Diluted earnings per common share - weighted-average shares and assumed conversions (in shares)	83,408	83,164	82,670
Basic earnings per common share (in dollars per share)	$ 1.03	$ 0.84	$ 0.75
Diluted earnings per common share (in dollars per share)	$ 1.02	$ 0.84	$ 0.74