Note 12 - Fair Value of Financial Instruments (Detail) - Fair Value of Financial Instruments (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011	Dec. 31, 2010
Financial Assets
Cash and due from banks	$ 114,646	$ 117,888	$ 208,873	$ 87,347
Securities held-to-maturity	849,376	1,153,504
Securities available-for-sale	1,293,571	1,294,478
Securities available-for-sale	1,293,571
Loans held-for-sale		760
Investment in Federal Home Loan Bank stock	45,493	52,989
Financial Liabilities
Deposits	7,353,041	7,229,131
Securities sold under agreements to repurchase	1,350,000	1,400,000
Advances from Federal Home Loan Bank	21,200	225,000
Long-term debt	171,136	171,136
Carrying Amount [Member]
Financial Assets
Cash and due from banks	114,646	117,888
Short-term investments	426,456	294,956
Short-term investments	426,456	294,956
Securities held-to-maturity	849,376	1,153,504
Securities available-for-sale	1,293,571	1,294,478
Trading securities	4,619	4,542
Loans held-for-sale		760
Loans, net	7,066,456	6,844,483
Investment in Federal Home Loan Bank stock	45,493	52,989
Warrants	114	218
Option contracts	6,424	3,026
Foreign exchange contracts	184,711	238,581
Financial Liabilities
Deposits	7,353,041	7,229,131
Securities sold under agreements to repurchase	1,350,000	1,400,000
Advances from Federal Home Loan Bank	21,200	225,000
Other borrowings	18,746	19,800
Long-term debt	171,136	171,136
Option contracts	7,097	1,282
Interest rate swaps		300,000
Foreign exchange contracts	142,234	128,215
Off-Balance Sheet Financial Instruments
Commitments to extend credit	1,734,352	1,626,523
Standby letters of credit	43,282	62,076
Other letters of credit	83,311	64,233
Bill of lading guarantees	9	187
Fair Value [Member]
Financial Assets
Cash and due from banks	114,646	117,888
Short-term investments	426,456	294,956
Short-term investments	426,456	294,956
Securities held-to-maturity	908,067	1,203,977
Securities available-for-sale	1,293,571	1,294,478
Trading securities	4,619	4,542
Loans held-for-sale		760
Loans, net	7,015,190	6,825,571
Investment in Federal Home Loan Bank stock	45,493	52,989
Warrants	114	218
Option contracts	56	34
Foreign exchange contracts	2,401	2,151
Financial Liabilities
Deposits	7,359,427	7,240,857
Securities sold under agreements to repurchase	1,477,535	1,547,900
Advances from Federal Home Loan Bank	21,843	227,825
Other borrowings	16,069	19,801
Long-term debt	98,392	98,676
Option contracts	49	5
Interest rate swaps		2,634
Foreign exchange contracts	1,018	486
Off-Balance Sheet Financial Instruments
Commitments to extend credit	(1,457)	(1,253)
Standby letters of credit	(244)	(367)
Other letters of credit	(39)	(38)
Bill of lading guarantees		$ 0