Note 19 - Stockholders' Equity (Details Textual) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Stockholders' Equity Attributable to Parent, Ending Balance	$ 2,342,448	$ 2,199,297	$ 2,342,448	$ 2,199,297	$ 2,313,037	$ 2,294,283	$ 2,163,329	$ 2,121,866
Stockholders' Equity, Period Increase (Decrease), Total			48,200
Net Income (Loss) Attributable to Parent, Total	54,321	72,244	101,173	138,923
Other Comprehensive Income (Loss), Net of Tax, Total	(1,524)	9,073	6,051	16,648
Proceeds from Issuance of Common Stock, Dividend Reinvestment Plan			1,707	1,681
Dividends, Common Stock, Cash	$ 24,672	$ 24,754	49,332	49,721
Payments for Repurchase of Common Stock			$ 12,880	$ 31,609