Note 19 - Stockholders' Equity (Details Textual) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Stockholders' Equity Attributable to Parent, Ending Balance	$ 2,163,329	$ 2,009,792	$ 2,121,866	$ 1,973,304
Stockholders' Equity, Period Increase (Decrease), Total	41,500
Net Income (Loss) Attributable to Parent, Total	66,679	63,816
Other Comprehensive Income (Loss), Net of Tax, Total	7,575	(9,321)
Proceeds from Issuance of Common Stock, Dividend Reinvestment Plan	835	664
Dividends, Common Stock, Cash	24,967	19,468
Payments for Repurchase of Common Stock	$ 8,601