Note 4 - Loans and ACL for Loans (Details Textual) - USD ($)		12 Months Ended
		Dec. 31, 2024	Dec. 31, 2023
Loans and Leases Receivable, Deferred Expense (Income)		$ 3,000,000	$ 2,000,000
Continuing Involvement with Transferred Financial Assets, Principal Amount Outstanding		$ 2,000,000	4,000,000
Financing Receivable, Accrued Interest, after Allowance for Credit Loss, Statement of Financial Position [Extensible Enumeration]		Accrued interest receivable
Financing Receivable, Accrued Interest, after Allowance for Credit Loss		$ 23,000,000	21,000,000
Financing Receivable, before Allowance for Credit Loss	[1]	6,520,402,000	5,771,038,000
Financing Receivable, Nonaccrual, Interest Income		0	0
Mortgage Loans in Process of Foreclosure, Amount		569,000	668,000
Asset Pledged as Collateral [Member] | Federal Home Loan Bank Advances [Member]
Financing Receivable, before Allowance for Credit Loss		$ 3,480,000,000	$ 3,150,000,000

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