Note 12 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments - USD ($)	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014	Dec. 31, 2013
Financial Assets
Cash and due from banks	$ 166,933,000	$ 176,830,000	$ 245,860,000	$ 153,747,000
Cash and due from banks	166,933,000	176,830,000
Short-term investments	48,711,000	489,614,000
Short-term investments	48,711,000	489,614,000
Securities available-for-sale	1,545,699,000	1,318,935,000
Loans held for sale	0	973,000
Loans held for sale		1,225,000
Loans, net	9,338,364,000	8,740,268,000
Loans, net	9,271,167,000	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	32,000	27,000
Warrants	32,000	27,000
Foreign exchange contracts	193,066,000	167,005,000
Foreign exchange contracts	2,326,000	1,876,000
Deposits	9,338,863,000	8,783,460,000
Deposits	9,341,551,000	8,785,342,000
Securities sold under agreements to repurchase	400,000,000	450,000,000
Securities sold under agreements to repurchase	419,915,000	473,816,000
Advances from Federal Home Loan Bank	210,000,000	425,000,000
Advances from Federal Home Loan Bank	210,020,000	424,974,000
Other borrowings	20,261,000	19,934,000
Other borrowings	17,571,000	17,978,000
Long-term debt	119,136,000	119,136,000
Long-term debt	59,015,000	59,425,000
Foreign exchange contracts	188,048,000	178,868,000
Foreign exchange contracts	3,201,000	5,007,000
Interest rate swaps	298,538,000	300,480,000
Interest rate swaps	4,095,000	4,626,000
Off-Balance Sheet Financial Instruments
Commitments to extend credit	2,003,486,000	2,071,766,000
Commitments to extend credit	(4,123,000)	(3,442,000)
Standby letters of credit	50,293,000	53,910,000
Standby letters of credit	(202,000)	(243,000)
Other letters of credit	57,204,000	48,142,000
Other letters of credit	(35,000)	(29,000)
Bill of lading guarantees	199,000	$ 108,000
Bill of lading guarantees	$ (1,000)