Note 13 - Fair Value Measurements and Fair Value of Financial Instruments - Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands		Mar. 31, 2021	Dec. 31, 2020
Equity securities		$ 20,993	$ 23,744
Warrants		3,615	3,409
Foreign exchange contracts with gain		154,340	151,244
Foreign exchange contracts with gain, fair value		2,891	4,658
Interest rate swaps		496,140	96,889
Interest rate swaps, fair value		3,615	3,409
Foreign exchange contracts with loss		96,119	132,813
Foreign exchange contracts with loss, fair value		2,550	2,200
Interest rate swaps		662,228	679,648
Interest rate swaps, fair value		12,116	10,286
Commitments to extend credit		3,095,013	2,977,528
Commitments to extend credit, fair value		(9,614)	(8,432)
Standby letters of credit		237,488	234,200
Standby letters of credit, fair value		(1,720)	(1,630)
Other letters of credit		21,975	16,821
Other letters of credit, fair value		(19)	(16)
Bill of lading guarantees		0	238
Bill of lading guarantees, fair value		0	0
Reported Value Measurement [Member]
Cash and due from banks		141,885	138,616
Short-term investments		1,612,411	1,282,462
Securities available-for-sale		908,844	1,036,550
Loans, net		15,497,712	15,475,364
Equity securities		20,993	23,744
Investment in Federal Home Loan Bank stock		17,250	17,250
Deposits		16,353,633	16,109,401
Advances from Federal Home Loan Bank		75,000	150,000
Other borrowings		23,333	23,714
Long-term debt		119,136	119,136
Reported Value Measurement [Member] | Warrants [Member]
Warrants		16	21
Estimate of Fair Value Measurement [Member]
Cash and due from banks		141,885	138,616
Short-term investments		1,612,411	1,282,462
Securities available-for-sale		908,844	1,036,550
Loans, net	[1]	16,094,374	16,103,471
Equity securities		20,993	23,744
Investment in Federal Home Loan Bank stock		17,250	17,250
Deposits		16,364,101	16,125,808
Advances from Federal Home Loan Bank		77,691	155,133
Other borrowings		19,861	19,632
Long-term debt		64,892	65,487
Estimate of Fair Value Measurement [Member] | Warrants [Member]
Warrants		$ 16	$ 21

[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.