Note 12 - Fair Value of Financial Instruments (Detail) - Fair Value of Financial Instruments (USD $) In Thousands, unless otherwise specified							3 Months Ended	12 Months Ended
	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011	Dec. 31, 2010	Mar. 31, 2012 Carrying Amount [Member]	Dec. 31, 2011 Carrying Amount [Member]	Mar. 31, 2012 Fair Value [Member]	Dec. 31, 2011 Fair Value [Member]
Financial Assets
Cash and due from banks	$ 119,106	$ 117,888	$ 87,111	$ 87,347	$ 119,106	$ 117,888
Cash and due from banks							119,106	117,888
Short-term investments					275,056	294,956	275,056	294,956
Short-term investments					275,056	294,956	275,056	294,956
Securities purchased under agreements to resell	50,000				50,000	0
Securities purchased under agreements to resell							50,000	0
Securities held-to-maturity	1,084,708	1,153,504			1,084,708	1,153,504
Securities held-to-maturity							1,131,524	1,203,977
Securities available-for-sale	1,353,742	1,294,478			1,353,742	1,294,478
Securities available-for-sale	1,353,742						1,353,742	1,294,478
Trading securities					104,453	4,542
Trading securities							104,453	4,542
Loans held-for-sale	3,709	760			3,709	760
Loans held-for-sale							3,709	760
Loans, net					6,705,880	6,844,483
Loans, net							6,681,964	6,825,571
Investment in Federal Home Loan Bank stock	50,456	52,989			50,456	52,989
Investment in Federal Home Loan Bank stock							50,456	52,989
Warrants					163	218
Warrants							163	218
Option contracts					4,595	3,026
Option contracts							25	34
Foreign exchange contracts					159,241	238,581
Foreign exchange contracts							1,680	2,151
Financial Liabilities
Deposits	7,359,774	7,229,131			7,359,774	7,229,131
Deposits							7,370,498	7,240,857
Securities sold under agreements to repurchase	1,400,000	1,400,000			1,400,000	1,400,000	1,541,580	1,547,900
Advances from Federal Home Loan Bank		225,000				225,000
Advances from Federal Home Loan Bank								227,825
Other borrowings					18,868	19,800	18,868	19,801
Other borrowings					18,868	19,800	18,868	19,801
Long-term debt					171,136	171,136	94,970	98,676
Option contracts					932	1,282
Option contracts							1	5
Interest rate swaps					300,000	300,000
Interest rate swaps	1,800	2,600					1,845	2,634
Foreign exchange contracts					171,359	128,215
Foreign exchange contracts							1,353	486
Off-Balance Sheet Financial Instruments
Commitments to extend credit					1,727,202	1,626,523
Commitments to extend credit							(1,162)	(1,253)
Standby letters of credit					58,820	62,076
Standby letters of credit							(279)	(367)
Other letters of credit					67,753	64,233
Other letters of credit							(43)	(38)
Bill of lading guarantees					849	187
Bill of lading guarantees							$ (3)	$ 0