Note 10 - Borrowed Funds (Details) - USD ($)	9 Months Ended
	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Note 10 - Borrowed Funds (Details) [Line Items]
Securities Sold under Agreements to Repurchase	$ 400,000,000	$ 450,000,000
Weighted Average Rate of Securities Sold Under Agreements	3.89%	3.85%
Prepaid Security Sold Under Repurchase Agreement			$ 100,000,000
Rate of Prepaid Security Sold Under Repurchase Agreements			3.50%
Prepayment Penalty Security Sold Under Agreements to Repurchase	$ 0		$ 3,400,000
Federal Home Loan Bank, Advances, Maturities Summary, Due in Next Twelve Months	0	$ 400,000,000
Federal Home Loan Bank, Advances, Branch of FHLB Bank, Interest Rate		0.27%
Long-term Federal Home Loan Bank Advances	$ 75,000,000	$ 25,000,000
Federal Home Loan Bank, Advances, Branch of FHLB Bank, Weighted Average Interest Rate	0.87%	1.13%
Mature in July 2015 [Member]
Note 10 - Borrowed Funds (Details) [Line Items]
Long-term Federal Home Loan Bank Advances	$ 50,000,000
Mature in March 2018 [Member]
Note 10 - Borrowed Funds (Details) [Line Items]
Long-term Federal Home Loan Bank Advances	25,000,000
Callable Securities [Member]
Note 10 - Borrowed Funds (Details) [Line Items]
Securities Sold under Agreements to Repurchase	$ 200,000,000
Weighted Average Rate of Securities Sold Under Agreements		2.78%
Number of Floating-to-fixed Rate Agreements	4	4
Non Callable Fixed Rate Securities [Member]
Note 10 - Borrowed Funds (Details) [Line Items]
Securities Sold under Agreements to Repurchase		$ 200,000,000
Weighted Average Rate of Securities Sold Under Agreements	2.78%
Mature in August 2016 [Member]
Note 10 - Borrowed Funds (Details) [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Year Two	$ 50,000,000
Mature in July 2017 [Member]
Note 10 - Borrowed Funds (Details) [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Year Three	50,000,000
Mature in June 2018 [Member]
Note 10 - Borrowed Funds (Details) [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Year Four	50,000,000
Mature in July 2018 [Member]
Note 10 - Borrowed Funds (Details) [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Year Five	$ 50,000,000
Floating to Fixed Rate Agreements Totaling $200 Million [Member]
Note 10 - Borrowed Funds (Details) [Line Items]
Number of Floating-to-fixed Rate Agreements	4
Total Floating to Fixed Rate	$ 200,000,000
Debt, Weighted Average Interest Rate	5.00%
Floating Interest Rate, Range of Time Period	1 year
Floating to Fixed Rate Agreements Totaling $200 Million [Member] | Maximum [Member]
Note 10 - Borrowed Funds (Details) [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.07%
Floating to Fixed Rate Agreements Totaling $200 Million [Member] | Maximum [Member] | London Interbank Offered Rate (LIBOR) [Member]
Note 10 - Borrowed Funds (Details) [Line Items]
Debt Instrument, Basis Spread on Variable Rate	3.40%
Floating to Fixed Rate Agreements Totaling $200 Million [Member] | Minimum [Member]
Note 10 - Borrowed Funds (Details) [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.89%
Securities Sold under Agreements to Repurchase [Member]
Note 10 - Borrowed Funds (Details) [Line Items]
Investment Securities Pledged As Collateral	$ 439,800,000	$ 516,300,000