Note 18 - Stockholders' Equity (Details Textual) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019
Stockholders' Equity Attributable to Parent, Ending Balance	$ 2,463,289	$ 2,313,037	$ 2,418,144	$ 2,294,283
Stockholders' Equity, Period Increase (Decrease), Total	45,100
Net Income (Loss) Attributable to Parent, Total	73,384	46,852
Proceeds from Issuance of Common Stock, Dividend Reinvestment Plan	868	846
Dividends, Common Stock, Cash	24,650	24,660
Other Comprehensive Income (Loss), Net of Tax, Total	$ (3,624)	$ 7,575