Note 3 - Maturities of Investment Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
One year or less	$ 87,294
One year or less	87,350
One year or less	9,409
One year or less	9,417
After one through five years	219,404
After one through five years	221,094
After one through five years	56,352
After one through five years	56,393
After five through ten years	116,567
After five through ten years	120,081
After five through ten years	4,144
After five through ten years	4,314
After ten years	186,277
After ten years	195,681
After ten years	57,619
After ten years	58,429
Securities not due on a single maturity date	22,612
Securities not due on a single maturity date	23,087
Securities not due on a single maturity date	643,820
Securities not due on a single maturity date	652,425
Other securities (no maturity)	39,730
Other securities (no maturity)	40,394
Total	632,154	$ 705,373
Total	647,293	713,371
Total	811,074	824,992
Total	$ 821,372	$ 821,407