Note 6 - Investment Securities (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Investments, Debt and Equity Securities [Abstract]
Available-for-sale Securities	$ 1,203,682,000		$ 1,318,935,000
Investment Securities			1,320,000,000
Proceeds from Sale of Mortgage Backed Securities (MBS) categorized as Available-for-sale	406,900,000	123,700,000
Proceeds from Maturities, Prepayments and Calls of Mortgage Backed Securities (MBS)	12,100,000	20,500,000
Proceeds from Sales and Repayments of Other Investment Securities	335,100,000	16,000,000
Proceeds from Maturities Repayments and Calls of Other Investment Securities	0	112,900,000
Realized Gain from Sale and Call of Investment Securities	1,700,000	6,000,000
Realized Loss from Sale and Call of Investment Securities	1,700,000	67,000
Pledged Investment Securities	$ 575,500,000		$ 591,300,000