Note 4 - Securities Available-for-sale and Held-to-maturity By Contractual Maturity (Details) - USD ($)	Jun. 30, 2016	Dec. 31, 2015
Mutual Fund Debt Securities [Member]
Amortized Cost	$ 21,645,000	$ 21,290,000
Fair Value	21,645,000	21,290,000
Commercial Mortgage Backed Securities [Member]
Amortized Cost	568,503,000
Fair Value	580,500,000
Due in one year or less	6,370,000
Due in one year or less	6,370,000
Due after one year through five years	40,000
Due after one year through five years	40,000
Due after ten years	22,000,000
Amortized Cost	28,410,000	6,180,000
Other securities, fair value option	28,410,000	6,180,000
Due in one year or less
Due in one year or less
Due after one year through five years	1,810,000
Due after one year through five years	1,843,000
Due after five years through ten years	91,683,000
Due after five years through ten years	91,795,000
Due after ten years	251,673,000
Due after ten years	253,328,000
Total other securities	345,166,000
Total other securities	346,966,000
Amortized Cost	935,314,000	994,311,000
Fair Value	$ 949,111,000	$ 993,397,000