Note 14 - Fair Value Measurements and Fair Value of Financial Instruments - Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2026	Dec. 31, 2025
Securities AFS	$ 1,589,036	$ 1,658,223
Foreign exchange contracts with gain	162,570	176,037
Foreign exchange contracts with gain, fair value	247	211
Interest rate swaps	1,320,277	1,113,823
Interest rate swaps, fair value	40,142	26,472
Foreign exchange contracts with loss	31,334	37,991
Foreign exchange contracts with loss, fair value	178	73
Interest rate swaps	1,476,632	1,590,384
Interest rate swaps, fair value	36,243	28,917
Commitments to extend credit	4,199,716	3,809,999
Commitments to extend credit, fair value	(23,542)	(21,357)
Standby letters of credit	421,202	536,745
Standby letters of credit, fair value	(2,298)	(2,971)
Other letters of credit	6,050	4,442
Other letters of credit, fair value	(7)	(5)
Reported Value Measurement [Member]
Cash and due from banks	131,044	146,320
Short-term investments	1,576,961	1,278,089
Securities AFS	1,589,036	1,658,223
Loans held for sale	13,597	0
Loans held for investment, net	20,956,148	19,936,388
Equity securities	116,907	51,886
Investment in Federal Home Loan Bank stock	17,250	17,250
Deposits	21,834,988	20,894,167
Advances from Federal Home Loan Bank	200,000	0
Long-term debt	65,011	119,136
Estimate of Fair Value Measurement [Member]
Cash and due from banks	131,044	146,320
Short-term investments	1,576,961	1,278,089
Securities AFS	1,589,036	1,658,223
Loans held for sale	13,597	0
Loans held for investment, net	20,951,223	20,516,176
Equity securities	116,907	51,886
Investment in Federal Home Loan Bank stock	17,250	17,250
Deposits	21,793,721	20,884,386
Advances from Federal Home Loan Bank	200,723	0
Long-term debt	$ 41,802	$ 79,818