Note 13 - Fair Value of Financial Instruments (Details) - Fair Value Hierarchy of Financial Instruments - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Financial Assets
Cash and due from banks	$ 196,342	$ 176,830
Short-term investments	369,829	489,614
Securities available-for-sale	1,380,879	1,318,935
Loans held-for-sale		1,225
Loans, net	9,815,077	8,688,072
Investment in Federal Home Loan Bank stock	17,250	30,785
Warrants	37	27
Financial Liabilities
Deposits	10,243,411	8,785,342
Securities sold under agreement to repurchase	418,403	473,816
Advances from Federal Home Loan Bank	75,220	424,974
Other borrowings	16,291	17,978
Long-term debt	58,420	59,425
Fair Value, Inputs, Level 1 [Member]
Financial Assets
Cash and due from banks	196,342	176,830
Short-term investments	369,829	489,614
Securities available-for-sale	290,890	669,870
Fair Value, Inputs, Level 2 [Member]
Financial Assets
Securities available-for-sale	1,089,989	649,065
Investment in Federal Home Loan Bank stock	17,250	30,785
Financial Liabilities
Securities sold under agreement to repurchase	418,403	473,816
Advances from Federal Home Loan Bank	75,220	424,974
Long-term debt	58,420	59,425
Fair Value, Inputs, Level 3 [Member]
Financial Assets
Loans held-for-sale		1,225
Loans, net	9,815,077	8,688,072
Warrants	37	27
Financial Liabilities
Deposits	10,243,411	8,785,342
Other borrowings	$ 16,291	$ 17,978