Note 18 - Stockholders' Equity (Details Textual) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Stockholders' Equity Attributable to Parent, Ending Balance	$ 2,116,775		$ 2,116,775		$ 1,973,304
Stockholders' Equity, Period Increase (Decrease), Total			143,500
Net Income (Loss) Attributable to Parent, Total	69,757	$ 49,746	207,237	$ 150,102
Dividends, Common Stock, Cash			58,500
Other Comprehensive Income (Loss), Net of Tax, Total	$ (862)	$ 1,203	$ (12,198)	$ 3,498
Class of Warrant or Right, Number of Securities Called by Warrants or Rights	345,534		345,534		943,327
U.S. Treasury [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights	1,846,374		1,846,374
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 20.96		$ 20.96		$ 20.41
Class of Warrant or Right, Increase in Warrants Exercisable, Percentage					1.03%