Note 12 - Fair Value of Financial Instruments (Details) - Fair Value Hierarchy of Financial Instruments (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Financial Assets
Cash and due from banks	$ 200,302	$ 153,747
Short-term investments	597,747	516,938
Securities available-for-sale	1,340,092	1,586,668
Trading securities		4,936
Loans, net	8,576,545	7,760,490
Investment in Federal Home Loan Bank stock	34,090	25,000
Warrants	12	30
Financial Liabilities
Deposits	8,692,118	7,977,639
Securities sold under agreement to repurchase	576,670	852,835
Advances from Federal Home Loan Bank	555,000	521,560
Other borrowings	15,853	16,107
Long-term debt	59,425	58,970
Fair Value, Inputs, Level 1 [Member]
Financial Assets
Cash and due from banks	200,302	153,747
Short-term investments	597,747	516,938
Securities available-for-sale	553,133	465,917
Fair Value, Inputs, Level 2 [Member]
Financial Assets
Securities available-for-sale	786,959	1,120,751
Trading securities		4,936
Investment in Federal Home Loan Bank stock	34,090	25,000
Financial Liabilities
Securities sold under agreement to repurchase	576,670	852,835
Advances from Federal Home Loan Bank	555,000	521,560
Long-term debt	59,425	58,970
Fair Value, Inputs, Level 3 [Member]
Financial Assets
Loans, net	8,576,545	7,760,490
Warrants	12	30
Financial Liabilities
Deposits	8,692,118	7,977,639
Other borrowings	$ 15,853	$ 16,107