Note 13 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments - USD ($)	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Dec. 31, 2013
Financial Assets
Cash and due from banks	$ 196,342,000	$ 176,830,000	$ 200,302,000	$ 153,747,000
Cash and due from banks	196,342,000	176,830,000
Short-term investments	369,829,000	489,614,000
Short-term investments	369,829,000	489,614,000
Securities available-for-sale	1,380,879,000	1,318,935,000
Loans held for sale	0	973,000
Loans held for sale		1,225,000
Loans, net	9,880,264,000	8,740,268,000
Loans, net	9,815,077,000	8,688,072,000
Investment in Federal Home Loan Bank stock	17,250,000	30,785,000
Investment in Federal Home Loan Bank stock	17,250,000	30,785,000
Warrants	37,000	27,000
Warrants	37,000	27,000
Foreign exchange contracts	129,675,000	167,005,000
Foreign exchange contracts	3,363,000	1,876,000
Deposits	10,238,475,000	8,783,460,000
Deposits	10,243,411,000	8,785,342,000
Securities sold under agreements to repurchase	400,000,000	450,000,000
Securities sold under agreements to repurchase	418,403,000	473,816,000
Advances from Federal Home Loan Bank	75,000,000	425,000,000
Advances from Federal Home Loan Bank	75,220,000	424,974,000
Other borrowings	18,721,000	19,934,000
Other borrowings	16,291,000	17,978,000
Long-term debt	119,136,000	119,136,000
Long-term debt	58,420,000	59,425,000
Foreign exchange contracts	144,703,000	178,868,000
Foreign exchange contracts	4,895,000	5,007,000
Interest rate swaps	457,237,000	300,480,000
Interest rate swaps	11,000,000	4,626,000
Off-Balance Sheet Financial Instruments
Commitments to extend credit	1,853,080,000	2,071,766,000
Commitments to extend credit	(4,879,000)	(3,442,000)
Standby letters of credit	48,273,000	53,910,000
Standby letters of credit	(216,000)	(243,000)
Other letters of credit	58,204,000	48,142,000
Other letters of credit	(31,000)	(29,000)
Bill of lading guarantees	294,000	$ 108,000
Bill of lading guarantees	$ (1,000)