Note 12 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012	Dec. 31, 2011
Financial Assets
Cash and due from banks	$ 133,003	$ 144,909	$ 134,744	$ 117,888
Securities held-to-maturity		773,768
Securities held-to-maturity		823,906
Securities available-for-sale	2,018,305	1,291,480
Trading securities	4,816	4,703
Investment in Federal Home Loan Bank stock	32,918	41,272
Financial Liabilities
Deposits	7,710,521	7,383,225
Securities sold under agreements to repurchase	950,000	1,250,000
Advances from Federal Home Loan Bank	126,200	146,200
Long-term debt	171,136	171,136
Carrying Amount [Member]
Financial Assets
Cash and due from banks	133,003	144,909
Short-term investments	139,840	411,983
Short-term investments	139,840	411,983
Securities held-to-maturity	0	773,768
Securities available-for-sale	2,018,305	1,291,480
Trading securities	4,816	4,703
Loans, net	7,502,955	7,235,587
Investment in Federal Home Loan Bank stock	32,918	41,272
Warrants	72	104
Option contracts	510	105
Foreign exchange contracts	210,727	188,145
Financial Liabilities
Deposits	7,710,521	7,383,225
Securities sold under agreements to repurchase	950,000	1,250,000
Advances from Federal Home Loan Bank	126,200	146,200
Other borrowings	19,190	18,713
Long-term debt	171,136	171,136
Option contracts	0	104
Foreign exchange contracts	233,122	133,669
Off-Balance Sheet Financial Instruments
Commitments to extend credit	1,856,698	1,740,463
Standby letters of credit	48,282	44,672
Other letters of credit	65,758	71,073
Bill of lading guarantees	187	77
Fair Value [Member]
Financial Assets
Cash and due from banks	133,003	144,909
Short-term investments	139,840	411,983
Short-term investments	139,840	411,983
Securities held-to-maturity	0	823,906
Securities available-for-sale	2,018,305	1,291,480
Trading securities	4,816	4,703
Loans, net	7,418,305	7,169,732
Investment in Federal Home Loan Bank stock	32,918	41,272
Warrants	72	104
Option contracts	55	0
Foreign exchange contracts	3,177	2,924
Financial Liabilities
Deposits	7,711,375	7,389,015
Securities sold under agreements to repurchase	1,019,835	1,361,585
Advances from Federal Home Loan Bank	126,310	146,789
Other borrowings	14,680	14,573
Long-term debt	97,375	98,392
Option contracts	0	2
Foreign exchange contracts	6,233	1,586
Off-Balance Sheet Financial Instruments
Commitments to extend credit	(2,281)	(1,875)
Standby letters of credit	(156)	(204)
Other letters of credit	(33)	(34)
Bill of lading guarantees	$ 0	$ 0