Note 17 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Financial Assets
Cash and due from banks	$ 180,130	$ 176,830	$ 153,747	$ 144,909
Cash and due from banks	180,130	176,830
Short-term investments	536,880	489,614
Short-term investments	536,880	489,614
Securities available-for-sale	1,586,352	1,318,935
Loans held for sale	6,676	973
Loans held for sale	6,676	1,225
Loans, net	10,016,227	8,740,268
Loans, net	9,938,810	8,688,072
Investment in Federal Home Loan Bank stock	17,250	30,785
Investment in Federal Home Loan Bank stock	17,250	30,785
Warrants	62	27
Warrants	62	27
Foreign exchange contracts	100,602	167,005
Foreign exchange contracts	3,339	1,876
Financial Liabilities
Deposits	10,509,087	8,783,460
Deposits	10,509,879	8,785,342
Securities sold under agreements to repurchase	400,000	450,000
Securities sold under agreements to repurchase	413,417	473,816
Advances from Federal Home Loan Bank	275,000	425,000
Advances from Federal Home Loan Bank	274,488	424,974
Other borrowings	18,593	19,934
Other borrowings	16,684	17,978
Long-term debt	119,136	119,136
Long-term debt	58,420	59,425
Option contracts	9,396
Option contracts	28
Foreign exchange contracts	115,418	178,868
Foreign exchange contracts	4,124	5,007
Interest rate swaps	459,416	300,480
Interest rate swaps	6,496	4,626
Off-Balance Sheet Financial Instruments
Commitments to extend credit	1,971,848	2,071,766
Commitments to extend credit	(5,570)	(3,442)
Standby letters of credit	49,081	53,910
Standby letters of credit	(194)	(243)
Other letters of credit	38,131	48,142
Other letters of credit	(22)	(29)
Bill of lading guarantees	454	$ 108
Bill of lading guarantees	$ (1)