Note 6 - Investment Securities (Details) - Investments by Contractual Maturity Date - USD ($) $ in Thousands		Jun. 30, 2015	Dec. 31, 2014
Investments by Contractual Maturity Date [Abstract]
Due in one year or less		$ 299,913
Due in one year or less		300,112
Due after one year through five years		88,156
Due after one year through five years		89,227
Due after five years through ten years		45,607
Due after five years through ten years		44,609
Due after ten years (1)	[1]	1,113,966
Due after ten years (1)	[1]	1,111,751
Total		1,547,642	$ 1,324,408
Total		$ 1,545,699	$ 1,318,935

[1] Equity securities are reported in this category