Note 12 - Fair Value Measurements and Fair Value of Financial Instruments - Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023
Securities AFS	$ 1,653,167	$ 1,604,570
Equity securities	31,380	40,406	$ 40,400
Foreign exchange contracts with gain	250,648	124,452
Foreign exchange contracts with gain, fair value	334	379
Interest rate swaps	1,100,019	1,406,879
Interest rate swaps, fair value	55,138	54,268
Foreign exchange contracts with loss	66,081	101,378
Foreign exchange contracts with loss, fair value	186	175
Interest rate swaps	952,560	1,078,880
Interest rate swaps, fair value	42,014	45,762
Commitments to extend credit	3,925,285	3,808,620
Commitments to extend credit, fair value	(19,052)	(14,344)
Standby letters of credit	386,442	368,618
Standby letters of credit, fair value	(3,031)	(2,821)
Other letters of credit	19,450	11,308
Other letters of credit, fair value	(17)	(10)
Reported Value Measurement [Member]
Cash and due from banks	165,284	173,988
Short-term investments	1,010,651	654,813
Securities AFS	1,653,167	1,604,570
Loans held-for-sale	23,171	0
Loans held for investment, net	19,263,070	19,382,858
Equity securities	31,380	40,406
Investment in Federal Home Loan Bank stock	17,250	17,746
Deposits	19,846,259	19,325,447
Advances from Federal Home Loan Bank	265,000	540,000
Other borrowings	17,557	15,787
Long-term debt	119,136	119,136
Estimate of Fair Value Measurement [Member]
Cash and due from banks	165,284	173,988
Short-term investments	1,010,651	654,813
Securities AFS	1,653,167	1,604,570
Loans held-for-sale	23,171	0
Loans held for investment, net	19,597,530	19,605,152
Equity securities	31,380	40,406
Investment in Federal Home Loan Bank stock	17,250	17,746
Deposits	19,855,328	19,347,070
Advances from Federal Home Loan Bank	264,596	536,996
Other borrowings	15,373	13,978
Long-term debt	$ 73,102	$ 72,304