Note 12 - Other Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Schedule of Other Liabilities [Line Items]
Current federal income taxes	$ 133,500	$ 96,740
Deferred ceding commission	89,710	89,907
Amount payable on the return of cash collateral under securities lending agreements	39,077	19,357
Accrued compensation	32,069	67,687
FHLB advances	25,550	0
Other	92,887	80,154
Total other liabilities	$ 412,793	$ 353,845