Note 13 - Fair Value Measurements and Fair Value of Financial Instruments - Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands		Sep. 30, 2021	Dec. 31, 2020
Securities available-for-sale		$ 1,079,216	$ 1,036,550
Equity securities		20,117	23,744
Warrants		5,187	3,409
Foreign exchange contracts with gain		161,535	151,244
Foreign exchange contracts with gain, fair value		1,319	4,658
Interest rate swaps		664,288	96,889
Interest rate swaps, fair value		5,187	3,409
Foreign exchange contracts with loss		70,184	132,813
Foreign exchange contracts with loss, fair value		1,723	2,200
Interest rate swaps		788,802	679,648
Interest rate swaps, fair value		9,037	10,286
Commitments to extend credit		3,255,421	2,977,528
Commitments to extend credit, fair value		(11,020)	(8,432)
Standby letters of credit		248,958	234,200
Standby letters of credit, fair value		(2,172)	(1,630)
Other letters of credit		25,205	16,821
Other letters of credit, fair value		(15)	(16)
Bill of lading guarantees		0	238
Bill of lading guarantees, fair value		0	0
Reported Value Measurement [Member]
Cash and due from banks		156,287	138,616
Short-term investments		1,667,875	1,282,462
Securities available-for-sale		1,079,216	1,036,550
Loans, net		15,976,781	15,475,364
Equity securities		20,117	23,744
Investment in Federal Home Loan Bank stock		17,250	17,250
Deposits		17,006,870	16,109,401
Advances from Federal Home Loan Bank		20,000	150,000
Other borrowings		23,197	23,714
Long-term debt		119,136	119,136
Reported Value Measurement [Member] | Warrants [Member]
Warrants		22	21
Estimate of Fair Value Measurement [Member]
Cash and due from banks		156,287	138,616
Short-term investments		1,667,875	1,282,462
Securities available-for-sale		1,079,216	1,036,550
Loans, net	[1]	16,301,993	16,103,471
Equity securities		20,117	23,744
Investment in Federal Home Loan Bank stock		17,250	17,250
Deposits		17,007,694	16,125,808
Advances from Federal Home Loan Bank		20,856	155,133
Other borrowings		19,164	19,632
Long-term debt		62,274	65,487
Estimate of Fair Value Measurement [Member] | Warrants [Member]
Warrants		$ 22	$ 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.