Note 14 - Fair Value of Financial Instruments - Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands		Jun. 30, 2019	Dec. 31, 2018
Cash and due from banks		$ 206,123	$ 225,333
Securities available-for-sale		1,471,584	1,242,509
Loans, net	[1]	14,814,173	13,928,162
Equity securities		32,498	25,098
Investment in Federal Home Loan Bank stock		17,250	17,250
Warrants		1,440	7,810
Foreign exchange contracts with gain		109,659	86,875
Foreign exchange contracts with gain, fair value		638	397
Interest rate swaps		1	467,410
Interest rate swaps, fair value		1,440	7,810
Deposits		14,417,628	13,754,028
Advances from Federal Home Loan Bank		551,591	529,500
Other borrowings		43,084	34,031
Long-term debt		121,592	132,615
Option contracts		1,698	1,215
Option contracts, fair value		14	6
Foreign exchange contracts with loss		95,600	94,977
Foreign exchange contracts with loss, fair value		876	1,763
Interest rate swaps		5	265,166
Interest rate swaps, fair value		13,779	1,543
Commitments to extend credit		3,019,604	2,691,579
Commitments to extend credit, fair value		(8,916)	(8,843)
Standby letters of credit		255,584	245,087
Standby letters of credit, fair value		(2,630)	(2,662)
Other letters of credit		24,086	35,759
Other letters of credit, fair value		(21)	(30)
Bill of lading guarantees		188	730
Bill of lading guarantees, fair value		0	0
Warrants [Member]
Warrants		44
Reported Value Measurement [Member]
Cash and due from banks		206,123	225,333
Short-term investments		351,603	374,957
Securities available-for-sale		1,471,584	1,242,509
Loans, net	[1]	14,469,444	13,871,832
Equity securities		32,498	25,098
Investment in Federal Home Loan Bank stock		17,250	17,250
Deposits		14,362,922	13,702,340
Advances from Federal Home Loan Bank		550,000	530,000
Other borrowings		49,663	35,756
Long-term debt		169,761	189,448
Reported Value Measurement [Member] | Warrants [Member]
Warrants		44	184
Estimate of Fair Value Measurement [Member]
Cash and due from banks		206,123	225,333
Short-term investments		351,603	374,957
Securities available-for-sale		1,471,584	1,242,509
Loans, net	[1]	14,814,173	13,928,162
Equity securities		32,498	25,098
Investment in Federal Home Loan Bank stock		17,250	17,250
Deposits		14,417,628	13,754,028
Advances from Federal Home Loan Bank		551,591	529,500
Other borrowings		43,084	34,031
Long-term debt		121,592	132,615
Estimate of Fair Value Measurement [Member] | Warrants [Member]
Warrants		$ 44	$ 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.