Note 10 - Stockholders' Equity (Details Textual) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025	Jun. 30, 2026	Dec. 31, 2025	Jun. 30, 2025	Dec. 31, 2024
Equity, Attributable to Parent	$ 3,056,745	$ 2,902,276	$ 3,056,745	$ 2,902,276	$ 3,046,614	$ 2,925,388	$ 2,886,295	$ 2,845,704
Stockholders' Equity, Period Increase (Decrease)			131,400
Net Income (Loss) Attributable to Parent	95,174	77,651	274,269	224,607
Other Comprehensive Income (Loss), Net of Tax			5,900
Share-Based Payment Arrangement, Expense			5,800
Proceeds from Issuance of Common Stock, Dividend Reinvestment Plan			1,988	1,970
Stock Issued During Period, Value, Issued for Services, Net	1	0	864	1,020
Treasury Stock, Value, Acquired, Cost Method	50,749	50,585	77,505	127,923
Dividends, Common Stock, Cash	25,208	23,243	76,093	70,944
Share-Based Payment Arrangement, Decrease for Tax Withholding Obligation	$ 1,444	$ 3	$ 3,878	$ 2,758