Note 9 - Borrowed Funds (Details Textual) $ in Thousands	3 Months Ended
Jun. 30, 2016 USD ($)	Dec. 31, 2015 USD ($)
Non Callable Fixed Rate Securities [Member]
Securities Sold under Agreements to Repurchase	$ 200,000	$ 200,000
Weighted Average Rate Of Securities Sold Under Agreements	2.78%	2.78%
Floating to Fixed Rate Agreements Totaling 200 Million [Member] \| Maximum [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument, Basis Spread on Variable Rate	3.40%
Floating to Fixed Rate Agreements Totaling 200 Million [Member] \| Maximum [Member]
Debt Instrument, Interest Rate, Stated Percentage	5.07%
Floating to Fixed Rate Agreements Totaling 200 Million [Member] \| Minimum [Member]
Debt Instrument, Interest Rate, Stated Percentage	4.89%
Floating to Fixed Rate Agreements Totaling 200 Million [Member]
Number Of Floating To Fixed Rate Agreements	4,000,000
Total Floating to Fixed Rate	$ 200,000
Debt, Weighted Average Interest Rate	5.00%
Floating Interest Rate Range of Time Period	1 year
Federal Funds Purchased and Securities Sold under Agreements to Repurchase [Member]
Investment Securities Pledged As Collateral	$ 454,000	$ 430,000
Mature in August 2016 [Member]
Number Of Securities Sold Under Agreements To Repurchase	4
Long-term Debt, Maturities, Repayments of Principal in Year Two	$ 50,000
Long-term Debt, Maturities, Repayments of Principal in Year Three	50,000
Long-term Debt, Maturities, Repayments of Principal in Year Four	50,000
Long-term Debt, Maturities, Repayments of Principal in Year Five	50,000
Over-night Borrowings [Member]
Advances from Federal Home Loan Banks	$ 230,000	$ 250,000
Federal Home Loan Bank, Advances, Branch of FHLB Bank, Interest Rate	0.47%	0.27%
At Fixed Rate [Member]
Advances from Federal Home Loan Banks	$ 325,000	$ 25,000
Mature in July 2016 [Member]
Advances from Federal Home Loan Banks	300,000
Mature in March 2018 [Member]
Advances from Federal Home Loan Banks	25,000
Securities Sold under Agreements to Repurchase	$ 400,000	$ 400,000
Weighted Average Rate Of Securities Sold Under Agreements	3.89%	3.89%
Advances from Federal Home Loan Banks	$ 555,000	$ 275,000
Federal Home Loan Bank, Advances, Branch of FHLB Bank, Interest Rate	0.44%	1.13%

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Amount of borrowings as of the balance sheet date from the Federal Home Loan Bank, which are primarily used to cover shortages in the required reserve balance and liquidity shortages.

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