Note 4 - Securities Available-for-sale and Held-to-maturity by Contractual Maturity (Details) - USD ($)	Mar. 31, 2016	Dec. 31, 2015
Mutual Fund Debt Securities [Member]
Amortized Cost	$ 21,507,000	$ 21,290,000
Fair Value	21,507,000	21,290,000
Commercial Mortgage Backed Securities [Member]
Amortized Cost	657,089,000
Fair Value	668,412,000
Due in one year or less	6,845,000
Due in one year or less	6,845,000
Due after one year through five years	1,040,000
Due after one year through five years	1,040,000
Total securities held-to-maturity	7,885,000	6,180,000
Other securities, fair value option	7,885,000	6,180,000
Due in one year or less	5,993,000
Due in one year or less	6,003,000
Due after one year through five years	1,825,000
Due after one year through five years	1,855,000
Due after five years through ten years	74,821,000
Due after five years through ten years	74,261,000
Due after ten years	269,144,000
Due after ten years	269,225,000
Total other securities	351,783,000
Total other securities	351,344,000
Amortized Cost	1,030,379,000	994,311,000
Fair Value	$ 1,041,263,000	$ 993,397,000