Note 3 - Investment Securities (Details) - Maturities of Investment Securities (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Maturities of Investment Securities [Abstract]
One year or less	$ 41,310
One year or less	41,392
One year or less	58,762
One year or less	58,752
After one through five years	414,115
After one through five years	414,863
After one through five years	247,200
After one through five years	246,659
After five through ten years	182,259
After five through ten years	185,229
After five through ten years	123,795
After five through ten years	124,808
After ten years	264,739
After ten years	271,553
After ten years	243,476
After ten years	246,322
Other securities (no maturity)	31,098
Other securities (no maturity)	30,842
Total	902,423	777,587
Total	913,037	780,533
Total	704,331	307,481
Total	$ 707,383	$ 305,283