Note 3 - Investment Securities Available-for-Sale (Details) - USD ($)	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Note 3 - Investment Securities Available-for-Sale (Details) [Line Items]
Federal Home Loan Bank Stock and Federal Reserve Bank Stock	$ 16,865,000	$ 10,657,000	$ 22,560,000
Debt Securities, Weighted Average Duration	3 years 255 days
Available-for-sale Securities, Gross Realized Gains	$ 2,500,000	116,000
Available-for-sale Securities, Gross Realized Losses	294,000	106,000
Proceeds from Sale of Available-for-sale Securities	65,800,000	$ 17,500,000
Available-for-sale Securities Pledged as Collateral	450,500,000
Securities Holdings of any One Issuer Exceeding 10% of Shareholders' Equity	$ 0		$ 0
Debt Securities [Member] | Total Investment Securities [Member] | Investment Securities Concentration Risk [Member]
Note 3 - Investment Securities Available-for-Sale (Details) [Line Items]
Concentration Risk, Percentage	99.90%