Note 3 - Investment Securities (Details) - Maturities of Investment Securities - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Maturities of Investment Securities [Abstract]
One year or less	$ 28,739
One year or less	28,807
One year or less	28,543
One year or less	28,512
After one through five years	315,065
After one through five years	314,557
After one through five years	88,911
After one through five years	88,048
After five through ten years	127,795
After five through ten years	130,087
After five through ten years	13,727
After five through ten years	13,899
After ten years	209,000
After ten years	215,350
After ten years	5,363
After ten years	5,412
Securities not due on a single maturity date	24,774
Securities not due on a single maturity date	24,570
Securities not due on a single maturity date	650,619
Securities not due on a single maturity date	647,426
Other securities (no maturity)	0
Other securities (no maturity)	0
Other securities (no maturity)	38,629
Other securities (no maturity)	38,110
Total	705,373	$ 777,587
Total	713,371	780,533
Total	825,792	307,481
Total	$ 821,407	$ 305,283