Note 14 - Fair Value of Financial Instruments - Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands		Mar. 31, 2019	Dec. 31, 2018
Cash and due from banks		$ 194,928	$ 225,333
Securities available-for-sale		1,309,853	1,242,509
Loans, net	[1]	14,373,444	13,928,162
Equity securities		29,261	25,098
Investment in Federal Home Loan Bank stock		17,250	17,250
Warrants		4,480	7,810
Foreign exchange contracts with gain		76,768	86,875
Foreign exchange contracts with gain, fair value		459	397
Interest rate swaps		358,509	467,410
Interest rate swaps, fair value		4,480	7,810
Deposits		14,143,470	13,754,028
Advances from Federal Home Loan Bank		420,450	529,500
Other borrowings		42,361	34,031
Long-term debt		123,897	132,615
Option contracts		2,188	1,215
Option contracts, fair value		12	6
Foreign exchange contracts with loss		57,273	94,977
Foreign exchange contracts with loss, fair value		645	1,763
Interest rate swaps		346,357	265,166
Interest rate swaps, fair value		5,727	1,543
Commitments to extend credit		2,776,325	2,691,579
Commitments to extend credit, fair value		(5,703)	(8,843)
Standby letters of credit		260,268	245,087
Standby letters of credit, fair value		(2,890)	(2,662)
Other letters of credit		29,354	35,759
Other letters of credit, fair value		(28)	(30)
Bill of lading guarantees		662	730
Bill of lading guarantees, fair value
Warrants [Member]
Warrants		181
Reported Value Measurement [Member]
Cash and due from banks		194,928	225,333
Short-term investments		343,452	374,957
Securities available-for-sale		1,309,853	1,242,509
Loans, net	[2]	14,153,318	13,871,832
Equity securities		29,261	25,098
Investment in Federal Home Loan Bank stock		17,250	17,250
Deposits		14,086,364	13,702,340
Advances from Federal Home Loan Bank		420,000	530,000
Other borrowings		48,099	35,756
Long-term debt		174,448	189,448
Reported Value Measurement [Member] | Warrants [Member]
Warrants		181	184
Estimate of Fair Value Measurement [Member]
Cash and due from banks		194,928	225,333
Short-term investments		343,452	374,957
Securities available-for-sale		1,309,853	1,242,509
Loans, net	[2]	14,373,444	13,928,162
Equity securities		29,261	25,098
Investment in Federal Home Loan Bank stock		17,250	17,250
Deposits		14,143,470	13,754,028
Advances from Federal Home Loan Bank		420,450	529,500
Other borrowings		42,361	34,031
Long-term debt		123,897	132,615
Estimate of Fair Value Measurement [Member] | Warrants [Member]
Warrants		$ 181	$ 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.

[2] 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.