Note 7 - Net Income Per Share - Net Income Per Share Basic and Diluted (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Net income	$ 144,430	$ 121,163	$ 337,337	$ 330,469
Weighted-average outstanding shares — basic (in shares)	48,757	47,780	48,692	47,501
Effect of dilutive securities (in shares)	207	1,012	253	1,233
Weighted-average outstanding shares — diluted (in shares)	48,964	48,792	48,945	48,734
Earnings per share, basic (in dollars per share)	$ 2.96	$ 2.54	$ 6.93	$ 6.96
Earnings per share, diluted (in dollars per share)	$ 2.95	$ 2.48	$ 6.89	$ 6.78