Note 14 - Fair Value of Financial Instruments - Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands		Mar. 31, 2020	Dec. 31, 2019
Equity securities		$ 18,790	$ 28,005
Warrants		3,210	2,181
Foreign exchange contracts with gain		110,465	146,397
Foreign exchange contracts with gain, fair value		1,157	2,411
Interest rate swaps		32,346	130,401
Interest rate swaps, fair value		3,210	2,181
Option contracts		2,496	908
Option contracts, fair value		14	7
Foreign exchange contracts with loss		216,401	127,003
Foreign exchange contracts with loss, fair value		4,211	1,415
Interest rate swaps		713,337	602,291
Interest rate swaps, fair value		32,304	14,229
Commitments to extend credit		2,934,789	3,077,081
Commitments to extend credit, fair value		(9,176)	(9,826)
Standby letters of credit		261,096	282,352
Standby letters of credit, fair value		(2,180)	(2,431)
Other letters of credit		19,878	22,209
Other letters of credit, fair value		(17)	(20)
Bill of lading guarantees		89	319
Bill of lading guarantees, fair value		0	(1)
Reported Value Measurement [Member]
Cash and due from banks		136,350	177,240
Short-term investments		363,666	416,538
Securities available-for-sale		1,355,173	1,451,842
Loans, net	[1]	15,385,662	14,951,631
Equity securities		18,790	28,005
Investment in Federal Home Loan Bank stock		17,250	18,090
Deposits		15,090,150	14,692,308
Short-term borrowings		12,898	25,683
Advances from Federal Home Loan Bank		495,000	670,000
Other borrowings		36,697	36,666
Long-term debt		119,136	119,136
Reported Value Measurement [Member] | Warrants [Member]
Warrants		24	39
Estimate of Fair Value Measurement [Member]
Cash and due from banks		136,350	177,240
Short-term investments		363,666	416,538
Securities available-for-sale		1,355,173	1,451,842
Loans, net	[1]	15,588,186	15,444,752
Equity securities		18,790	28,005
Investment in Federal Home Loan Bank stock		17,250	18,090
Deposits		15,133,137	14,719,452
Short-term borrowings		12,898	25,683
Advances from Federal Home Loan Bank		502,934	674,530
Other borrowings		31,323	30,764
Long-term debt		56,317	76,058
Estimate of Fair Value Measurement [Member] | Warrants [Member]
Warrants		$ 24	$ 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.