Note 17 - Fair Value of Financial Instruments (Detail) - Fair Value of Financial Instruments (USD $)	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Financial Assets
Cash and due from banks	$ 144,909,000	$ 117,888,000	$ 87,347,000	$ 100,124,000
Securities held-to-maturity	773,768,000	1,153,504,000
Securities available-for-sale	1,291,480,000	1,294,478,000
Securities available-for-sale	1,291,480,000
Loans held-for-sale		760,000
Investment in Federal Home Loan Bank stock	41,272,000	52,989,000
Deposits	7,383,225,000	7,229,131,000
Securities sold under agreement to repurchase	1,250,000,000	1,400,000,000
Advances from Federal Home Loan Bank	146,200,000	225,000,000
Other borrowings		880,000
Long-term debt	171,136,000	171,136,000
Carrying Amount [Member]
Financial Assets
Cash and due from banks	144,909,000	117,888,000
Short-term investments	411,983,000	294,956,000
Short-term investments	411,983,000	294,956,000
Securities held-to-maturity	773,768,000	1,153,504,000
Securities available-for-sale	1,291,480,000	1,294,478,000
Trading securities	4,703,000	4,542,000
Loans held-for-sale		760,000
Loans, net	7,235,587,000	6,844,483,000
Investment in Federal Home Loan Bank stock	41,272,000	52,989,000
Warrants	104,000	218,000
Option contracts	105,000	3,026,000
Foreign exchange contracts	188,145,000	238,581,000
Deposits	7,383,225,000	7,229,131,000
Securities sold under agreement to repurchase	1,250,000,000	1,400,000,000
Advances from Federal Home Loan Bank	146,200,000	225,000,000
Other borrowings	18,713,000	19,800,000
Long-term debt	171,136,000	171,136,000
Option contracts	104,000	1,282,000
Interest rate swaps		300,000,000
Foreign exchange contracts	133,669,000	128,215,000
Off-Balance Sheet Financial Instruments
Commitments to extend credit	1,740,463,000	1,626,523,000
Standby letters of credit	44,672,000	62,076,000
Other letters of credit	71,073,000	64,233,000
Bill of lading guarantees	77,000	187,000
Fair Value [Member]
Financial Assets
Cash and due from banks	144,909,000	117,888,000
Short-term investments	411,983,000	294,956,000
Short-term investments	411,983,000	294,956,000
Securities held-to-maturity	823,906,000	1,203,977,000
Securities available-for-sale	1,291,480,000	1,294,478,000
Trading securities	4,703,000	4,542,000
Loans held-for-sale		760,000
Loans, net	7,169,732,000	6,825,571,000
Investment in Federal Home Loan Bank stock	41,272,000	52,989,000
Warrants	104,000	218,000
Option contracts		34,000
Foreign exchange contracts	2,924,000	2,151,000
Deposits	7,389,015,000	7,240,857,000
Securities sold under agreement to repurchase	1,361,585,000	1,547,900,000
Advances from Federal Home Loan Bank	146,789,000	227,825,000
Other borrowings	14,573,000	19,801,000
Long-term debt	98,392,000	98,676,000
Option contracts	2,000	5,000
Interest rate swaps		2,634,000
Foreign exchange contracts	1,586,000	486,000
Off-Balance Sheet Financial Instruments
Commitments to extend credit	(1,875,000)	(1,253,000)
Standby letters of credit	(204,000)	(367,000)
Other letters of credit	(34,000)	(38,000)
Bill of lading guarantees		$ 0