Note 4 - Loans (Details Textual) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2021 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)
Unamortized Loan Commitment and Origination Fees and Unamortized Discounts or Premiums, Total	$ 761		$ 879
Financing Receivable, Number of Payment Deferrals	26		82
Financing Receivable, Deferred Payments	$ 4,100		$ 9,500
Loans and Leases Receivable, Impaired, Interest Lost on Nonaccrual Loans	44	$ 58
Mortgage Loans in Process of Foreclosure, Amount	109		80
Financing Receivable, Troubled Debt Restructuring	$ 6,000		$ 6,100
Financing Receivable, Number of Contracts Qualified as Troubled Debt Restructuring	90
Troubled Debt Restructurings Percentage of Gross Portfolio Loans	0.52%		0.53%
Impaired Financing Receivable, Recorded Investment, Total	$ 7,959		$ 11,103
Percentage of Collateral Coverage to Loan Balance to Consider Restructured Loan to Performing and Accrual Status	100.00%
Doubtful Grade Remaining Outstanding Period, Minimum (Month)	6 months
Percentage of Unallocated Allowance Amount out of Allowance for Loan and Lease Losses	4.00%		4.00%
Loans and Leases Receivable, Allowance, Ending Balance	$ 17,027		$ 16,910
Percentage of Allowance for Loan and Lease Losses out of Net Loans	1.49%		1.48%
Fair Value Disclosure, Off-balance Sheet Risks, Amount, Asset	$ 281,400		$ 267,800
Reserve for Unfunded Commitments Included in Other Liabilities	800		800
Loans and Leases Receivable, Gross, Total	$ 1,145,943		1,139,732
Maximum Loan to Value, Percentage	80.00%
Percentage of Loan Portfolio Secured by Real Estate	78.00%
Percentage of Loan Portfolio Secured by Real Estate, Excluding PPP Loans	87.00%
Residential Portfolio Segment [Member]
Impaired Financing Receivable, Recorded Investment, Total	$ 5,207		5,318
Loans and Leases Receivable, Gross, Total	101,001		103,854
Residential Portfolio Segment [Member] | Real Estate Loan [Member] | Individual Tax Identification Number Loan [Member]
Financing Receivable, Troubled Debt Restructuring	$ 4,700
Financing Receivable, Number of Contracts Qualified as Troubled Debt Restructuring	82
Loans and Leases Receivable, Gross, Total	$ 27,839		29,035
Commercial Real Estate Portfolio Segment [Member]
Impaired Financing Receivable, Recorded Investment, Total	$ 721		3,734
Financing Receivable, Troubled Debt Restructuring, Subsequent Default, Number of Contracts	1
Financing Receivable, Troubled Debt Restructuring, Subsequent Default	$ 626
Loans and Leases Receivable, Gross, Total	$ 789,669		767,536
SBA CARES Act Paycheck Protection Program [Member]
Number of Customers Participated in PPP	424
Loans and Leases Receivable, Gross, Total	$ 117,991		130,814
Performing Financial Instruments [Member]
Financing Receivable, Number of Contracts Qualified as Troubled Debt Restructuring	88
Impaired Financing Receivable, Recorded Investment, Total	$ 4,000		4,100
Loans and Leases Receivable, Gross, Total	1,142,019		1,132,719
Performing Financial Instruments [Member] | Residential Portfolio Segment [Member] | Real Estate Loan [Member] | Individual Tax Identification Number Loan [Member]
Loans and Leases Receivable, Gross, Total	26,310		27,450
Performing Financial Instruments [Member] | SBA CARES Act Paycheck Protection Program [Member]
Loans and Leases Receivable, Gross, Total	117,991		130,814
Federal Home Loan Bank of San Francisco [Member]
Loans Pledged as Collateral	557,300		523,500
Merchants Holding Company [Member]
Unamortized Loan Commitment and Origination Fees and Unamortized Discounts or Premiums, Total	810		$ 920
Accretion (Amortization) of Discounts and Premiums, Acquired Loans	$ 110	$ 163