Note 3 - Loans and Allowance for Credit Losses on Loans (Details Textual) Pure in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Dec. 31, 2023 USD ($)
Financing Receivable, Accrued Interest, after Allowance for Credit Loss		$ 22,000,000		$ 22,000,000		$ 21,000,000
Financing Receivable, before Allowance for Credit Loss	[1]	6,278,133,000		6,278,133,000		5,771,038,000
Loans and Leases Receivable, Related Parties		74,000,000		74,000,000		62,000,000
Financing Receivable, Nonaccrual, Interest Income		0	$ 0	0	$ 0
Mortgage Loans in Process of Foreclosure, Amount		311,000		$ 311,000		668,000
Financing Receivable, Modifications, Number of Contracts				0	0
Financing Receivable, Troubled Debt Restructuring, Subsequent Default, Number of Contracts				0	0
Asset Pledged as Collateral [Member] | Federal Home Loan Bank Advances [Member]
Financing Receivable, before Allowance for Credit Loss		$ 3,320,000,000		$ 3,320,000,000		$ 3,150,000,000

[1] (1) Total loans are presented inclusive of premiums, discounts and net loan origination fees and costs.