Note 4 - Investment Securities (Details) - Investments by Contractual Maturity Date - USD ($) $ in Thousands		Dec. 31, 2015	Dec. 31, 2014
Investments by Contractual Maturity Date [Abstract]
Due in one year or less		$ 184,963
Due in one year or less		184,956
Due after one year through five years		135,698
Due after one year through five years		135,924
Due after five years through ten years		195,539
Due after five years through ten years		192,291
Due after ten years (1)	[1]	1,079,523
Due after ten years (1)	[1]	1,073,181
Total		1,595,723	$ 1,324,408
Total		$ 1,586,352	$ 1,318,935

[1] Equity securities are reported in this category