Note 12 - Fair Value of Financial Instruments - Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016		Jun. 30, 2016	Dec. 31, 2015
Cash and due from banks	$ 160,517	$ 218,017		$ 229,411	$ 180,130
Cash and due from banks, fair value	160,517	218,017
Short-term investments	393,895	967,067
Securities available-for-sale	1,368,351	1,314,345	[1]
Loans held for sale		7,500
Loans held for sale, fair value		7,500
Loans, net	11,451,635	11,077,315
Loans, net, fair value	11,379,583	11,006,344
Investment in Federal Home Loan Bank stock	17,250	17,250
Investment in Federal Home Loan Bank stock, fair value	17,250	17,250
Warrants	108	79
Warrants, fair value	108	79
Foreign exchange contracts with gain, fair value	2,378	1,302
Foreign exchange contracts with gain	157,508	82,439
Interest rate swaps	206,263	361,526
Interest rate swaps, fair value	1,608	938
Deposits	11,463,317	11,674,726
Deposits, fair value	11,470,912	11,680,017
Securities sold under agreements to repurchase	150,000	350,000
Securities sold under agreements to repurchase, fair value	150,842	351,989
Advances from Federal Home Loan Bank	475,000	350,000
Advances from Federal Home Loan Bank, fair value	475,058	350,062
Other borrowings	17,564	17,662
Other borrowings, fair value	15,570	15,944
Long-term debt	119,136	119,136
Long-term debt, fair value	63,337	63,169
Option contracts	13,598	12,117
Option contracts, fair value	231	121
Foreign exchange contracts with loss	45,869	89,545
Foreign exchange contracts with loss, fair value	640	3,132
Interest rate swaps	358,994	119,136
Interest rate swaps, fair value	7,191	3,744
Commitments to extend credit	2,102,122	2,062,241
Commitments to extend credit, fair value	(6,446)	(6,025)
Standby letters of credit	97,642	75,396
Standby letters of credit, fair value	(995)	(668)
Other letters of credit	31,498	37,283
Other letters of credit, fair value	(17)	(16)
Bill of lading guarantees, fair value
Bill of lading guarantees	$ 113	$ 75

[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.