Note 4 - Loans (Details Textual) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Unamortized Loan Commitment and Origination Fees and Unamortized Discounts or Premiums, Total	$ 1,000		$ 1,000		$ 1,500
Financing Receivable, Number of Payment Deferrals	107		107
Financing Receivable, Deferred Payments	$ 38,600		$ 38,600
Financing Receivable, Troubled Debt Restructuring	$ 6,300		$ 6,300		$ 6,500
Financing Receivable, Number of Contracts Qualified as Troubled Debt Restructuring	92		92
Troubled Debt Restructurings Percentage of Gross Portfolio Loans	0.52%		0.52%		0.63%
Troubled Debt Restructurings Percentage of Gross Portfolio Loans, Excluding PPP Loans	0.61%		0.61%
Impaired Financing Receivable, Recorded Investment, Total	$ 12,357		$ 12,357		$ 10,399
Percentage of Collateral Coverage to Loan Balance to Consider Restructured Loan to Performing and Accrual Status			100.00%
Financing Receivable, Modifications, Number of Contracts		0	1	1
Financing Receivable, Troubled Debt Restructuring, Subsequent Default, Number of Contracts	0
Mortgage Loans in Process of Foreclosure, Amount	$ 81		$ 81		$ 100
Percentage of Unallocated Allowance Amount out of Allowance for Loan and Lease Losses					3.00%
Loans and Leases Receivable, Allowance, Ending Balance	$ 16,873		$ 16,873		$ 12,231
Percentage of Allowance for Loan and Lease Losses out of Net Loans	1.40%		1.40%		1.18%
Percentage of Allowance for Loan and Lease Losses out of Net Loans, Excluding PPP Loans	1.62%		1.62%
Fair Value Disclosure, Off-balance Sheet Risks, Amount, Asset	$ 263,100		$ 263,100		$ 275,100
Reserve for Unfunded Commitments Included in Other Liabilities	800		800		695
Loans and Leases Receivable, Gross, Total	$ 1,206,065		$ 1,206,065		1,032,903
Maximum Loan to Value, Percentage			80.00%
Percentage of Loan Portfolio Secured by Real Estate	74.00%		74.00%
Percentage of Loan Portfolio Secured by Real Estate, Excluding PPP Loans	86.00%		86.00%
Provision for Unfunded Commitments			$ 105	$ 0
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Troubled Debt Restructuring	$ 650		650
Impaired Financing Receivable, Recorded Investment, Total	4,812		$ 4,812		3,103
Financing Receivable, Modifications, Number of Contracts			1
Loans and Leases Receivable, Gross, Total	788,823		$ 788,823		739,583
SBA CARES Act Paycheck Protection Program [Member]
Loans and Leases Receivable, Gross, Total	$ 163,493		$ 163,493		0
Number of Customers Participated in PPP	606		606
Performing Financial Instruments [Member]
Financing Receivable, Number of Contracts Qualified as Troubled Debt Restructuring	91		91
Impaired Financing Receivable, Recorded Investment, Total	$ 4,300		$ 4,300		4,800
Loans and Leases Receivable, Gross, Total	1,197,967		1,197,967		1,027,287
Performing Financial Instruments [Member] | SBA CARES Act Paycheck Protection Program [Member]
Loans and Leases Receivable, Gross, Total	163,493		163,493
Merchants Holding Company [Member]
Unamortized Loan Commitment and Origination Fees and Unamortized Discounts or Premiums, Total	1,100		1,100		1,700
Accretion (Amortization) of Discounts and Premiums, Acquired Loans	233	$ 193	612	$ 431
Federal Home Loan Bank of San Francisco [Member]
Loans Pledged as Collateral	$ 527,500		$ 527,500		$ 542,100