Note 14 - Fair Value Measurements and Fair Value of Financial Instruments - Fair Value Hierarchy of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2026	Dec. 31, 2025
Equity Securities, FV-NI	$ 27,246	$ 32,754
Estimate of Fair Value Measurement [Member]
Cash and due from banks	131,044	146,320
Short-term investments	1,576,961	1,278,089
Loans held for investment, net	20,951,223	20,516,176
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
Equity Securities, FV-NI		1,539
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Cash and due from banks	131,044	146,320
Short-term investments	1,576,961	1,278,089
Loans held for investment, net	0	0
Investment in Federal Home Loan Bank stock	0	0
Deposits	0	0
Advances from Federal Home Loan Bank	0
Long-term debt	0	0
Equity Securities, FV-NI		0
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Cash and due from banks	0	0
Short-term investments	0	0
Loans held for investment, net	0	0
Investment in Federal Home Loan Bank stock	17,250	17,250
Deposits	0	0
Advances from Federal Home Loan Bank	200,723
Long-term debt	41,802	79,818
Equity Securities, FV-NI		0
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Cash and due from banks	0	0
Short-term investments	0	0
Loans held for investment, net	20,951,223	20,516,176
Investment in Federal Home Loan Bank stock	0	0
Deposits	21,793,721	20,884,386
Advances from Federal Home Loan Bank	0
Long-term debt	$ 0	0
Equity Securities, FV-NI		$ 1,539