Note 3 - Investment Securities (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Investments, Debt and Equity Securities [Abstract]
Securities Continuous Unrealized Loss Position Fair Value	$ 537,200,000
Securities Continuous Unrealized Loss Position Fair Value Percent of Portfolio	33.40%
Securities Sold under Agreements to Repurchase	104,400,000		93,500,000
Available-for-sale Securities Pledged as Collateral	888,600,000		520,400,000
Available-for-sale Securities, Gross Realized Gains	2,000	0
Available-for-sale Securities, Gross Realized Losses	$ 40,000	$ 0