Note 19 - Stockholders' Equity (Details Textual) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Stockholders' Equity Attributable to Parent, Ending Balance	$ 2,199,297	$ 2,064,833	$ 2,199,297	$ 2,064,833	$ 2,163,329	$ 2,121,866	$ 2,009,792	$ 1,973,304
Stockholders' Equity, Period Increase (Decrease), Total			77,400
Net Income (Loss) Attributable to Parent, Total	72,244	73,664	138,923	137,480
Other Comprehensive Income (Loss), Net of Tax, Total	9,073	(2,015)	16,648	(11,336)
Proceeds from Issuance of Common Stock, Dividend Reinvestment Plan			1,681	1,325
Dividends, Common Stock, Cash	$ 24,754	$ 19,498	49,721	38,966
Payments for Repurchase of Common Stock			$ 31,609	$ (0)