Note 4 - Investment Securities - Investments by Contractual Maturity Date (Details) - USD ($) $ in Thousands		Dec. 31, 2016	Dec. 31, 2015
Due in one year or less, Amortized Cost		$ 339,879
Due in one year or less, Fair Value		339,823
Due after one year through five years, Amortized Cost		553,130
Due after one year through five years, Fair Value		544,585
Due after five years through ten years, Amortized Cost		75,111
Due after five years through ten years, Fair Value		72,733
Due after ten years (1), Amortized Cost	[1]	348,892
Due after ten years (1), Fair Value	[1]	357,204
Total, Amortized Cost		1,317,012	$ 1,595,723
Total, Fair Value		$ 1,314,345	$ 1,586,352	[2]

[1] Equity securities are reported in this category

[2] Preferred stock of government sponsored entities and other equity securities as of December 31, 2015 were reclassified as level 1 rather than level 2 as originally classified due to the availability of quoted prices in active markets.