Note 12 - Fair Value of Financial Instruments - Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2014
Cash and due from banks	$ 203,877	$ 180,130	$ 196,342	$ 176,830
Cash and due from banks	203,877	180,130
Short-term investments	791,757	536,880
Short-term investments	791,757	536,880
Available-for-sale Securities	1,298,469	1,586,352
Total, Fair Value	1,298,469	1,586,352
Loans held for sale	4,750	6,676
Loans held for sale	4,750	6,676
Loans, net	10,886,996	10,016,227
Loans, net	10,825,059	9,938,810
Investment in Federal Home Loan Bank stock	18,900	17,250
Investment in Federal Home Loan Bank stock	18,900	17,250
Warrants	75	62
Warrants	75	62
Foreign exchange contracts with gain	107,064	100,602
Foreign exchange contracts with gain	1,711	3,339
Deposits	10,938,696	10,509,087
Deposits	10,946,853	10,509,879
Securities Sold under Agreements to Repurchase	350,000	400,000
Securities sold under agreements to repurchase	355,422	413,417
Advances from Federal Home Loan Banks	700,000	275,000
Advances from Federal Home Loan Bank	700,130	274,488
Other borrowings	17,705	18,593
Other borrowings	15,903	16,684
Long-term debt	119,136	119,136
Long-term debt	62,628	58,420
Option contracts		9,396
Option contracts		28
Foreign exchange contracts with loss	44,985	115,418
Foreign exchange contracts with loss	712	4,124
Interest rate swaps	477,479	459,416
Interest rate swaps	15,186	6,496
Commitments to extend credit	1,950,756	1,971,848
Commitments to extend credit	(5,844)	(5,570)
Standby letters of credit	74,612	49,081
Standby letters of credit	(839)	(194)
Other letters of credit	31,331	38,131
Other letters of credit	(69)	(22)
Bill of lading guarantees		454
Bill of lading guarantees		$ (1)