Note 14 - Fair Value of Financial Instruments - Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands		Jun. 30, 2020	Dec. 31, 2019
Equity securities		$ 24,570	$ 28,005
Warrants		3,842	2,181
Foreign exchange contracts with gain		101,020	146,397
Foreign exchange contracts with gain, fair value		1,529	2,411
Interest rate swaps		50,599	130,401
Interest rate swaps, fair value		3,842	2,181
Option contracts		530	908
Option contracts, fair value		6	7
Foreign exchange contracts with loss		179,211	127,003
Foreign exchange contracts with loss, fair value		531	1,415
Interest rate swaps		697,212	602,291
Interest rate swaps, fair value		33,760	14,229
Commitments to extend credit		3,073,581	3,077,081
Commitments to extend credit, fair value		(9,464)	(9,826)
Standby letters of credit		262,028	282,352
Standby letters of credit, fair value		(1,981)	(2,431)
Other letters of credit		28,199	22,209
Other letters of credit, fair value		(30)	(20)
Bill of lading guarantees		124	319
Bill of lading guarantees, fair value		0	(1)
Reported Value Measurement [Member]
Cash and due from banks		148,700	177,240
Short-term investments		1,425,001	416,538
Securities available-for-sale		1,146,102	1,451,842
Loans, net	[1]	15,434,096	14,951,631
Equity securities		24,570	28,005
Investment in Federal Home Loan Bank stock		17,250	18,090
Deposits		16,281,904	14,692,308
Short-term borrowings		0	25,683
Advances from Federal Home Loan Bank		230,000	670,000
Other borrowings		40,152	36,666
Long-term debt		119,136	119,136
Reported Value Measurement [Member] | Warrants [Member]
Warrants		13	39
Estimate of Fair Value Measurement [Member]
Cash and due from banks		148,700	177,240
Short-term investments		1,425,001	416,538
Securities available-for-sale		1,146,102	1,451,842
Loans, net	[1]	15,954,278	15,444,752
Equity securities		24,570	28,005
Investment in Federal Home Loan Bank stock		17,250	18,090
Deposits		16,334,769	14,719,452
Short-term borrowings		0	25,683
Advances from Federal Home Loan Bank		241,047	674,530
Other borrowings		33,040	30,764
Long-term debt		61,913	76,058
Estimate of Fair Value Measurement [Member] | Warrants [Member]
Warrants		$ 13	$ 39

[1] In accordance with the prospective adoption of ASU 2016-01, the fair value of loans as of December 31, 2019 & 2018 was measured using an exit price notion.