Note 16 - Fair Value of Financial Instruments - Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands		Dec. 31, 2019	Dec. 31, 2018
Equity securities		$ 28,005	$ 25,098
Warrants		2,181	7,810
Foreign exchange contracts with gain		146,397	86,875
Foreign exchange contracts with gain, fair value		2,411	397
Interest rate swaps		130,401	467,410
Interest rate swaps, fair value		2,181	7,810
Option contracts		908	1,215
Option contracts, fair value		7	6
Foreign exchange contracts with loss		127,003	94,977
Foreign exchange contracts with loss, fair value		1,415	1,763
Interest rate swaps		602,291	265,166
Interest rate swaps, fair value		14,229	1,543
Commitments to extend credit		3,077,081	2,691,579
Commitments to extend credit, fair value		(9,826)	(8,843)
Standby letters of credit		282,352	245,087
Standby letters of credit, fair value		(2,431)	(2,662)
Other letters of credit		22,209	35,759
Other letters of credit, fair value		(20)	(30)
Bill of lading guarantees		319	730
Bill of lading guarantees, fair value		(1)	0
Reported Value Measurement [Member]
Cash and due from banks		177,240	225,333
Short-term investments		416,538	374,957
Securities available-for-sale		1,451,842	1,242,509
Loans, net (1)	[1]	14,951,631	13,871,832
Equity securities		28,005	25,098
Investment in Federal Home Loan Bank stock		18,090	17,250
Deposits		14,692,308	13,702,340
Short-term borrowings		25,683	0
Advances from Federal Home Loan Bank		670,000	530,000
Other borrowings		36,666	35,756
Long-term debt		119,136	189,448
Reported Value Measurement [Member] | Warrants [Member]
Warrants		39	184
Estimate of Fair Value Measurement [Member]
Cash and due from banks		177,240	225,333
Short-term investments		416,538	374,957
Securities available-for-sale		1,451,842	1,242,509
Loans, net (1)	[1]	15,444,752	13,928,162
Equity securities		28,005	25,098
Investment in Federal Home Loan Bank stock		18,090	17,250
Deposits		14,719,452	13,754,028
Short-term borrowings		25,683	0
Advances from Federal Home Loan Bank		674,530	529,500
Other borrowings		30,764	34,031
Long-term debt		76,058	132,615
Estimate of Fair Value Measurement [Member] | Warrants [Member]
Warrants		$ 39	$ 184

[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.