Note 12 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013	Dec. 31, 2012
Financial Assets
Cash and due from banks	$ 200,302	$ 153,747	$ 201,815	$ 144,909
Cash and due from banks	200,302	153,747
Short-term investments	597,747	516,938
Short-term investments	597,747	516,938
Securities available-for-sale	1,340,092	1,586,668
Trading securities		4,936
Loans, net	8,576,545	7,760,490
Investment in Federal Home Loan Bank stock	34,090	25,000
Investment in Federal Home Loan Bank stock	34,090	25,000
Warrants	12	30
Deposits	8,694,669	7,981,305
Deposits	8,692,118	7,977,639
Securities sold under agreements to repurchase	550,000	800,000
Securities sold under agreements to repurchase	576,670	852,835
Advances from Federal Home Loan Bank	555,000	521,200
Advances from Federal Home Loan Bank	555,000	521,560
Other borrowings	15,853	16,107
Long-term debt	119,136	121,136
Long-term debt	59,425	58,970
Carrying Amount [Member]
Financial Assets
Cash and due from banks	200,302	153,747
Short-term investments	597,747	516,938
Short-term investments	597,747	516,938
Securities available-for-sale	1,340,092	1,586,668
Trading securities		4,936
Loans, net	8,676,153	7,897,187
Investment in Federal Home Loan Bank stock	34,090	25,000
Warrants	12	30
Option contracts		200
Foreign exchange contracts	183,753	267,644
Interest rate swaps	147,358
Deposits	8,694,669	7,981,305
Securities sold under agreements to repurchase	550,000	800,000
Advances from Federal Home Loan Bank	555,000	521,200
Other borrowings	18,882	19,062
Long-term debt	119,136	121,136
Foreign exchange contracts	201,240	236,350
Interest rate swaps	119,136
Off-Balance Sheet Financial Instruments
Commitments to extend credit	1,839,039	1,858,669
Standby letters of credit	54,304	45,058
Other letters of credit	49,623	54,098
Bill of lading guarantees	51	80
Fair Value [Member]
Financial Assets
Cash and due from banks	200,302	153,747
Short-term investments	597,747	516,938
Short-term investments	597,747	516,938
Securities available-for-sale	1,340,092	1,586,668
Trading securities		4,936
Loans, net	8,576,545	7,760,490
Investment in Federal Home Loan Bank stock	34,090	25,000
Warrants	12	30
Option contracts		0
Foreign exchange contracts	1,936	6,182
Interest rate swaps	442
Deposits	8,692,118	7,977,639
Securities sold under agreements to repurchase	576,670	852,835
Advances from Federal Home Loan Bank	555,000	521,560
Other borrowings	15,853	16,107
Long-term debt	59,425	58,970
Foreign exchange contracts	4,437	6,140
Interest rate swaps	280
Off-Balance Sheet Financial Instruments
Commitments to extend credit	(3,160)	(2,187)
Standby letters of credit	(331)	(205)
Other letters of credit	$ (29)	$ (34)