Note 12 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013	Dec. 31, 2012
Financial Assets
Cash and due from banks	$ 245,860	$ 153,747	$ 133,003	$ 144,909
Cash and due from banks	245,860	153,747
Short-term investments	803,576	516,938
Short-term investments	803,576	516,938
Securities available-for-sale	1,339,989	1,586,668
Trading securities		4,936
Loans, net	8,262,977	7,760,490
Investment in Federal Home Loan Bank stock	25,671	25,000
Investment in Federal Home Loan Bank stock	25,671	25,000
Warrants	21	30
Deposits	8,580,596	7,981,305
Deposits	8,578,747	7,977,639
Securities sold under agreements to repurchase	700,000	800,000
Securities sold under agreements to repurchase	733,020	852,835
Advances from Federal Home Loan Bank	521,200	521,200
Advances from Federal Home Loan Bank	521,966	521,560
Other borrowings	16,161	16,107
Long-term debt	119,136	121,136
Long-term debt	58,365	58,970
Carrying Amount [Member]
Financial Assets
Cash and due from banks	245,860	153,747
Short-term investments	803,576	516,938
Short-term investments	803,576	516,938
Securities available-for-sale	1,339,989	1,586,668
Trading securities		4,936
Loans, net	8,382,700	7,897,187
Investment in Federal Home Loan Bank stock	25,671	25,000
Warrants	21	30
Option contracts		200
Foreign exchange contracts	226,061	267,644
Deposits	8,580,596	7,981,305
Securities sold under agreements to repurchase	700,000	800,000
Advances from Federal Home Loan Bank	521,200	521,200
Other borrowings	18,985	19,062
Long-term debt	119,136	121,136
Foreign exchange contracts	161,760	236,350
Interest rate swaps	267,194
Commitments to extend credit	1,933,456	1,858,669
Standby letters of credit	47,983	45,058
Other letters of credit	59,445	54,098
Bill of lading guarantees	71	80
Fair Value [Member]
Financial Assets
Cash and due from banks	245,860	153,747
Short-term investments	803,576	516,938
Short-term investments	803,576	516,938
Securities available-for-sale	1,339,989	1,586,668
Trading securities		4,936
Loans, net	8,262,977	7,760,490
Investment in Federal Home Loan Bank stock	25,671	25,000
Warrants	21	30
Option contracts		0
Foreign exchange contracts	3,438	6,182
Deposits	8,578,747	7,977,639
Securities sold under agreements to repurchase	733,020	852,835
Advances from Federal Home Loan Bank	521,966	521,560
Other borrowings	16,161	16,107
Long-term debt	58,365	58,970
Foreign exchange contracts	1,594	6,140
Interest rate swaps	454
Commitments to extend credit	(2,856)	(2,187)
Standby letters of credit	(238)	(205)
Other letters of credit	$ (31)	$ (34)