Note 12 - Fair Value of Financial Instruments - Fair Value of Financial Instruments (Details) - USD ($)	Mar. 31, 2017	Dec. 31, 2016		Mar. 31, 2016	Dec. 31, 2015
Cash and due from banks	$ 190,522,000	$ 218,017,000		$ 192,642,000	$ 180,130,000
Cash and due from banks, fair value	190,522,000	218,017,000
Short-term investments	630,058,000	967,067,000
Securities available-for-sale	1,227,729,000	1,314,345,000	[1]	$ 1,300,000,000
Loans held for sale	5,835,000	7,500,000
Loans held for sale, fair value	5,835,000	7,500,000
Loans, net	11,245,570,000	11,077,315,000
Loans, net, fair value	11,170,158,000	11,006,344,000
Investment in Federal Home Loan Bank stock	17,250,000	17,250,000
Investment in Federal Home Loan Bank stock, fair value	17,250,000	17,250,000
Warrants	102,000	79,000
Warrants, fair value	102,000	79,000
Foreign exchange contracts with gain	174,021,000	82,439,000
Foreign exchange contracts with gain, fair value	1,148,000	1,302,000
Interest rate swaps	424,223,000	361,526,000
Interest rate swaps, fair value	1,851,000	938,000
Deposits	11,587,275,000	11,674,726,000
Deposits, fair value	11,595,618,000	11,680,017,000
Securities sold under agreements to repurchase	150,000,000	350,000,000
Securities sold under agreements to repurchase, fair value	149,982,000	351,989,000
Advances from Federal Home Loan Bank	325,000,000	350,000,000
Advances from Federal Home Loan Bank, fair value	325,053,000	350,062,000
Other borrowings	17,614,000	17,662,000
Other borrowings, fair value	15,865,000	15,944,000
Long-term debt	119,136,000	119,136,000
Long-term debt, fair value	63,076,000	63,169,000
Option contracts	11,679,000	12,117,000
Option contracts, fair value	180,000	121,000
Foreign exchange contracts with loss	70,325,000	89,545,000
Foreign exchange contracts with loss, fair value	647,000	3,132,000
Interest rate swaps	119,136,000	119,136,000
Interest rate swaps, fair value	3,228,000	3,744,000
Commitments to extend credit	2,126,106,000	2,062,241,000
Commitments to extend credit, fair value	(6,345,000)	(6,025,000)
Standby letters of credit	96,582,000	75,396,000
Standby letters of credit, fair value	(1,038,000)	(668,000)
Other letters of credit	23,639,000	37,283,000
Other letters of credit, fair value	(12,000)	(16,000)
Bill of lading guarantees	24,000	75,000
Bill of lading guarantees, fair value

[1] Preferred stock of government sponsored entities and other equity securities as of December 31, 2015 were reclassified as level 1 rather than level 2 as originally classified due to the availability of quoted prices in active markets.