Note 19 - Stockholders' Equity (Details Textual) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Stockholders' Equity Attributable to Parent, Ending Balance	$ 2,245,894	$ 2,116,777	$ 2,245,894	$ 2,116,777	$ 2,199,297	$ 2,121,866	$ 2,064,836	$ 1,973,304
Stockholders' Equity, Period Increase (Decrease), Total			124,000
Net Income (Loss) Attributable to Parent, Total	72,835	69,757	211,758	207,237
Other Comprehensive Income (Loss), Net of Tax, Total	525	(862)	17,173	(12,198)
Proceeds from Issuance of Common Stock, Dividend Reinvestment Plan			2,522	1,982
Dividends, Common Stock, Cash	$ 24,701	$ 19,532	74,422	58,498
Payments for Repurchase of Common Stock			$ 36,301	$ (0)