Note 3 - Investment Securities (Details) (USD $)	3 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Note 3 - Investment Securities (Details) [Line Items]
Securities Continuous Unrealized Loss Position Fair Value		$ 680,500,000	$ 715,300,000
Securities Continuous Unrealized Loss Position Fair Value Percent of Portfolio		62.80%	75.80%
Available-for-sale Securities Pledged as Collateral		520,400,000	587,900,000
Securities Sold under Agreements to Repurchase		93,500,000	102,800,000
Available-for-sale Securities, Gross Realized Gains		199,000	151,000	2,000
Available-for-sale Securities, Gross Realized Losses		191,000	302,000	0
Income Tax Benefit Related to Security Gains (Losses), Percentage	(39.225%)
Liquidation of the Acquired Investment Portfolio from SSB [Member]
Note 3 - Investment Securities (Details) [Line Items]
Marketable Securities, Realized Gain (Loss)			$ (193,000)