Note 12 - Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Jun. 03, 2016	Dec. 31, 2015	Jun. 30, 2015	Dec. 31, 2014
Cash and due from banks	$ 229,411		$ 180,130	$ 166,933	$ 176,830
Cash and due from banks	229,411		180,130
Short-term investments	706,927		536,880
Short-term investments	706,927		536,880
Available-for-sale Securities	1,241,904		1,586,352
Securities available-for-sale	1,241,904		1,586,352
Loans held for sale	2,925		6,676
Loans held for sale	2,925	$ 2,925	6,676
Total loans, net	10,393,473		10,016,227
Loans, net	10,328,509		9,938,810
Investment in Federal Home Loan Bank stock	17,250		17,250
Investment in Federal Home Loan Bank stock	17,250		17,250
Warrants	90		62
Warrants	90		62
Foreign exchange contracts with gain	85,098		100,602
Foreign exchange contracts with gain	2,083		3,339
Deposits	10,471,103		10,509,087
Deposits	10,482,519		10,509,879
Securities Sold under Agreements to Repurchase	400,000		400,000
Securities sold under agreements to repurchase	410,608		413,417
Advances from Federal Home Loan Banks	555,000		275,000
Advances from Federal Home Loan Bank	555,156		274,488
Other borrowings	17,748		18,593
Other borrowings	15,861		16,684
Long-term debt	119,136		119,136
Long-term debt	61,437		58,420
Option contracts			9,396
Option contracts			28
Foreign exchange contracts with loss	84,432		115,418
Foreign exchange contracts with loss	1,602		4,124
Interest rate swaps	479,683		459,416
Interest rate swaps	18,050		6,496
Commitments to extend credit	2,040,070		1,971,848
Commitments to extend credit	(5,639)		(5,570)
Standby letters of credit	76,574		49,081
Standby letters of credit	(300)		(194)
Other letters of credit	29,272		38,131
Other letters of credit	(20)		(22)
Bill of lading guarantees	51		454
Bill of lading guarantees	$ (1)		$ (1)