Note 14 - Fair Value of Financial Instruments - Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands		Sep. 30, 2019	Dec. 31, 2018
Cash and due from banks		$ 257,189	$ 225,333
Securities available-for-sale		1,427,438	1,242,509
Loans held-for-sale		36,778
Loans, net		15,004,114	13,928,162
Equity securities		32,862	25,098
Investment in Federal Home Loan Bank stock		17,250	17,250
Warrants		1,697	7,810
Foreign exchange contracts with gain		70,955	86,875
Foreign exchange contracts with gain, fair value		965	397
Interest rate swaps		139,466	467,410
Interest rate swaps, fair value		1,697	7,810
Deposits		14,703,977	13,754,028
Advances from Federal Home Loan Bank		603,014	529,500
Other borrowings		31,844	34,031
Long-term debt		113,409	132,615
Option contracts		1,172	1,215
Option contracts, fair value		6	6
Foreign exchange contracts with loss		121,769	94,977
Foreign exchange contracts with loss, fair value		2,435	1,763
Interest rate swaps		581,496	265,166
Interest rate swaps, fair value		17,734	1,543
Commitments to extend credit		3,097,207	2,691,579
Commitments to extend credit, fair value		(9,291)	(8,843)
Standby letters of credit		264,059	245,087
Standby letters of credit, fair value		(2,537)	(2,662)
Other letters of credit		29,230	35,759
Other letters of credit, fair value		(28)	(30)
Bill of lading guarantees		743	730
Bill of lading guarantees, fair value		0	0
Warrants [Member]
Warrants		31
Reported Value Measurement [Member]
Cash and due from banks		257,189	225,333
Short-term investments		567,957	374,957
Securities available-for-sale		1,427,438	1,242,509
Loans held-for-sale		36,778	0
Loans, net	[1]	14,601,565	13,871,832
Equity securities		32,862	25,098
Investment in Federal Home Loan Bank stock		17,250	17,250
Deposits		14,658,269	13,702,340
Advances from Federal Home Loan Bank		600,000	530,000
Other borrowings		38,369	35,756
Long-term debt		160,386	189,448
Reported Value Measurement [Member] | Warrants [Member]
Warrants		31	184
Estimate of Fair Value Measurement [Member]
Cash and due from banks		257,189	225,333
Short-term investments		567,957	374,957
Securities available-for-sale		1,427,438	1,242,509
Loans held-for-sale		36,778	0
Loans, net	[1]	15,004,114	13,928,162
Equity securities		32,862	25,098
Investment in Federal Home Loan Bank stock		17,250	17,250
Deposits		14,703,977	13,754,028
Advances from Federal Home Loan Bank		603,014	529,500
Other borrowings		31,844	34,031
Long-term debt		113,409	132,615
Estimate of Fair Value Measurement [Member] | Warrants [Member]
Warrants		$ 31	$ 184

[1] In accordance with the prospective adoption of ASU 2016-01, the fair value of loans as of December 31, 2018 was measured using an exit price notion. The fair value of loans as of December 31, 2017 was measured using an entry price notion.