Note 2 - Earnings per Common Share - Basic and Diluted Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2023	Jun. 30, 2022
Net income	$ 21,874	$ 22,502	$ 31,661	$ 27,533	$ 44,376	$ 59,194
Basic earnings per common share - weighted-average shares (in shares)	81,263		81,689		81,236	82,310
Effect of dilutive stock options (in shares)	149		326		158	307
Diluted earnings per common share - weighted-average shares and assumed conversions (in shares)	81,412		82,015		81,394	82,617
Basic earnings per common share (in dollars per share)	$ 0.27		$ 0.39		$ 0.55	$ 0.72
Diluted earnings per common share (in dollars per share)	$ 0.27		$ 0.39		$ 0.55	$ 0.72