Note 13 - Fair Value of Financial Instruments - Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Cash and due from banks	$ 167,886	$ 218,017
Securities available-for-sale	1,368,487	1,314,345
Loans held for sale		7,500
Loans, net	12,403,100	11,006,344
Investment in Federal Home Loan Bank stock	21,948	17,250
Investment in Federal Reserve Bank stock	8,733
Warrants	2,314	938
Foreign exchange contracts with gain	69,278	82,439
Foreign exchange contracts with gain, fair value	1,725	1,302
Interest rate swaps	155,671	361,526
Interest rate swaps, fair value	2,314	938
Deposits	12,573,127	11,680,017
Securities sold under agreements to repurchase	100,549	351,989
Advances from Federal Home Loan Bank	595,037	350,062
Other borrowings	151,643	15,944
Long-term debt	68,056	63,169
Option contracts	12,307	12,117
Option contracts, fair value	234	121
Foreign exchange contracts with loss	86,625	89,545
Foreign exchange contracts with loss, fair value	1,083	3,132
Interest rate swaps	510,841	119,136
Interest rate swaps, fair value	5,049	3,744
Commitments to extend credit	2,287,498	2,062,241
Commitments to extend credit, fair value	(6,924)	(6,025)
Standby letters of credit	140,682	75,396
Standby letters of credit, fair value	(1,699)	(668)
Other letters of credit	41,868	37,283
Other letters of credit, fair value	(218)	(16)
Bill of lading guarantees	24	75
Bill of lading guarantees, fair value
Warrants [Member]
Warrants	97
Reported Value Measurement [Member]
Cash and due from banks	167,886	218,017
Short-term investments	573,059	967,067
Securities available-for-sale	1,368,487	1,314,345
Loans held for sale		7,500
Loans, net	12,472,475	11,077,315
Investment in Federal Home Loan Bank stock	21,948	17,250
Investment in Federal Reserve Bank stock	8,733
Deposits	12,561,695	11,674,726
Securities sold under agreements to repurchase	100,000	350,000
Advances from Federal Home Loan Bank	595,000	350,000
Other borrowings	153,574	17,662
Long-term debt	119,136	119,136
Reported Value Measurement [Member] | Warrants [Member]
Warrants	97	79
Estimate of Fair Value Measurement [Member]
Cash and due from banks	167,886	218,017
Short-term investments	573,059	967,067
Securities available-for-sale	1,368,487	1,314,345
Loans held for sale		7,500
Loans, net	12,403,100	11,006,344
Investment in Federal Home Loan Bank stock	21,948	17,250
Investment in Federal Reserve Bank stock	8,733
Deposits	12,573,127	11,680,017
Securities sold under agreements to repurchase	100,549	351,989
Advances from Federal Home Loan Bank	595,037	350,062
Other borrowings	151,643	15,944
Long-term debt	68,056	63,169
Estimate of Fair Value Measurement [Member] | Warrants [Member]
Warrants	$ 97	$ 79