Note 16 - Fair Value of Financial Instruments - Fair Value of Financial Instruments (Details) - USD ($)	Dec. 31, 2016	Dec. 31, 2015		Dec. 31, 2014	Dec. 31, 2013
Cash and due from banks	$ 218,017,000	$ 180,130,000		$ 176,830,000	$ 153,747,000
Cash and due from banks, fair value	218,017,000	180,130,000
Short-term investments	967,067,000	536,880,000
Securities available-for-sale	1,314,345,000	1,586,352,000	[1]
Loans held for sale	7,500,000	6,676,000
Loans held for sale, fair value	7,500,000	6,676,000
Loans, net	11,077,315,000	10,016,227,000
Loans, net, fair value	11,006,344,000	9,938,810,000
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	79,000	62,000
Warrants, fair value	79,000	62,000
Foreign exchange contracts with gain	82,439,000	100,602,000
Foreign exchange contracts with gain, fair value	1,302,000	3,339,000
Interest rate swaps	361,526,000
Interest rate swaps, fair value	938,000
Deposits	11,674,726,000	10,509,087,000
Deposits, fair value	11,680,017,000	10,509,879,000
Securities sold under agreements to repurchase	350,000,000	400,000,000
Securities sold under agreements to repurchase, fair value	351,989,000	413,417,000
Advances from Federal Home Loan Bank	350,000,000	275,000,000
Advances from Federal Home Loan Bank, fair value	350,062,000	274,488,000
Other borrowings	17,662,000	18,593,000
Other borrowings, fair value	15,944,000	16,684,000
Long-term debt	119,136,000	119,136,000
Long-term debt, fair value	63,169,000	58,420,000
Option contracts	12,117,000	9,396,000
Option contracts, fair value	121,000	28,000
Foreign exchange contracts with loss	89,545,000	115,418,000
Foreign exchange contracts with loss, fair value	3,132,000	4,124,000
Interest rate swaps	119,136,000	459,416,000
Interest rate swaps, fair value	3,744,000	6,496,000
Commitments to extend credit	2,062,241,000	1,971,848,000
Commitments to extend credit, fair value	(6,025,000)	(5,570,000)
Standby letters of credit	75,396,000	49,081,000
Standby letters of credit, fair value	(668,000)	(194,000)
Other letters of credit	37,283,000	38,131,000
Other letters of credit, fair value	(16,000)	(22,000)
Bill of lading guarantees	75,000	454,000
Bill of lading guarantees, fair value	$ 0	$ (1,000)

[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.