Note 6 - Investment Securities (Details) - Investments by Contractual Maturity Date - USD ($) $ in Thousands		Mar. 31, 2016	Dec. 31, 2015
Investments by Contractual Maturity Date [Abstract]
Due in one year or less		$ 154,963
Due in one year or less		154,978
Due after one year through five years		104,879
Due after one year through five years		105,470
Due after five years through ten years		145,501
Due after five years through ten years		143,358
Due after ten years (1)	[1]	1,071,081
Due after ten years (1)	[1]	1,081,318
Total		1,476,424	$ 1,595,723
Total		$ 1,485,124	$ 1,586,352

[1] Equity securities are reported in this category