Note 10 - Borrowing Arrangements (Details Textual) - USD ($)		3 Months Ended		6 Months Ended
		Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Financing Receivable, before Allowance for Credit Loss	[1]	$ 3,047,712,000		$ 3,047,712,000		$ 3,031,861,000
Long-Term Federal Home Loan Bank Advances		$ 150,000,000		$ 150,000,000
Federal Home Loan Bank, Advances, Activity for Year, Average Interest Rate at Period End		1.18%		1.18%
Advances from Federal Home Loan Banks, Total		$ 150,000,000		$ 150,000,000		$ 150,000,000
Other Financial Institutions [Member]
Line of Credit Facility, Maximum Borrowing Capacity		$ 92,000,000		92,000,000
Federal Home Loan Bank Advances [Member]
Debt Instrument, Term (Year)		5 years
Interest Paid, Including Capitalized Interest, Operating and Investing Activities		$ 439,000	$ 579,000	878,000	$ 2,000,000
Unsecured Debt [Member] | Other Financial Institutions [Member]
Line of Credit Facility, Maximum Borrowing Capacity		80,000,000		80,000,000
Secured Debt [Member] | Other Financial Institutions [Member]
Line of Credit Facility, Maximum Borrowing Capacity		12,000,000		12,000,000
Federal Home Loan Bank Overnight Advances [Member]
Long-Term Federal Home Loan Bank Advances		0		0
Advances from Federal Home Loan Banks, Total		0		0
Asset Pledged as Collateral [Member] | Other Financial Institutions [Member]
Financing Receivable, before Allowance for Credit Loss		20,400,000		20,400,000
Federal Home Loan Bank Secured Line of Credit [Member]
Line of Credit Facility, Maximum Borrowing Capacity		939,700,000		939,700,000
Federal Home Loan Bank Secured Line of Credit [Member] | Asset Pledged as Collateral [Member]
Financing Receivable, before Allowance for Credit Loss		1,300,000		1,300,000
Federal Home Loan Bank of San Francisco Secured Line of Credit [Member]
Line of Credit Facility, Maximum Borrowing Capacity		45,900,000		45,900,000
Federal Home Loan Bank of San Francisco Secured Line of Credit [Member] | Asset Pledged as Collateral [Member]
Financing Receivable, before Allowance for Credit Loss		$ 64,000,000		$ 64,000,000

[1] Past due loans include nonaccrual loans and are therefore included in total loans.