Note 12 - Other Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Schedule of Other Liabilities [Line Items]
Current federal income taxes	$ 8,807	$ 96,740
Deferred ceding commission	92,070	89,907
Amount payable on the return of cash collateral under securities lending agreements	39,224	19,357
Accrued compensation	39,621	67,687
FHLB advances	115,308	0
Other	90,021	80,154
Total other liabilities	$ 385,051	$ 353,845