Note 3 - Investment Securities (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Note 3 - Investment Securities (Details) [Line Items]
Securities Continuous Unrealized Loss Position Fair Value	$ 872,400,000	$ 680,500,000
Securities Continuous Unrealized Loss Position Fair Value Percent of Portfolio	57.10%	62.80%
Available-for-sale Securities Pledged as Collateral	$ 840,400,000	$ 520,400,000
Securities Sold under Agreements to Repurchase	96,800,000	100,800,000
Available-for-sale Securities, Gross Realized Gains	350,000	199,000	$ 151,000
Available-for-sale Securities, Gross Realized Losses	$ 43,000	$ 191,000	302,000
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)