Note 6 - 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, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Net income	$ 178,274	$ 144,430	$ 445,791	$ 337,337
Basic (in shares)	47,898	48,757	47,879	48,692
Effect of dilutive securities (in shares)	144	207	143	253
Diluted (in shares)	48,042	48,964	48,022	48,945
Basic (in dollars per share)	$ 3.72	$ 2.96	$ 9.31	$ 6.93
Diluted (in dollars per share)	$ 3.71	$ 2.95	$ 9.28	$ 6.89