Note 12 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Financial Assets
Securities held-to-maturity		$ 823,906
Securities available-for-sale	1,743,309	1,291,480
Trading securities	4,855	4,703
Estimate of Fair Value Measurement [Member]
Financial Assets
Cash and due from banks	201,815	144,909
Short-term investments	389,024	411,983
Securities held-to-maturity		823,906
Securities available-for-sale	1,743,309	1,291,480
Trading securities	4,855	4,703
Loans, net	7,460,436	7,169,732
Investment in Federal Home Loan Bank stock	28,683	41,272
Warrants	49	104
Financial Liabilities
Deposits	7,917,105	7,389,015
Securities sold under agreement to repurchase	858,315	1,361,585
Advances from Federal Home Loan Bank	376,429	146,789
Other borrowings	16,020	14,573
Long-term debt	97,604	98,392
Fair Value, Inputs, Level 1 [Member]
Financial Assets
Cash and due from banks	201,815	144,909
Short-term investments	389,024	411,983
Securities held-to-maturity		0
Securities available-for-sale	466,145	526,165
Trading securities	0	0
Loans, net	0	0
Investment in Federal Home Loan Bank stock	0	0
Warrants	0	0
Financial Liabilities
Deposits	0	0
Securities sold under agreement to repurchase	0	0
Advances from Federal Home Loan Bank	0	0
Other borrowings	0	0
Long-term debt	0	0
Fair Value, Inputs, Level 2 [Member]
Financial Assets
Cash and due from banks	0	0
Short-term investments	0	0
Securities held-to-maturity		823,906
Securities available-for-sale	1,277,164	765,315
Trading securities	4,855	4,703
Loans, net	0	0
Investment in Federal Home Loan Bank stock	28,683	41,272
Warrants	0	0
Financial Liabilities
Deposits	0	0
Securities sold under agreement to repurchase	858,315	1,361,585
Advances from Federal Home Loan Bank	376,429	146,789
Other borrowings	0	0
Long-term debt	97,604	98,392
Fair Value, Inputs, Level 3 [Member]
Financial Assets
Cash and due from banks	0	0
Short-term investments	0	0
Securities held-to-maturity		0
Securities available-for-sale	0	0
Trading securities	0	0
Loans, net	7,460,436	7,169,732
Investment in Federal Home Loan Bank stock	0	0
Warrants	49	104
Financial Liabilities
Deposits	7,917,105	7,389,015
Securities sold under agreement to repurchase	0	0
Advances from Federal Home Loan Bank	0	0
Other borrowings	16,020	14,573
Long-term debt	$ 0	$ 0