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Loans and Allowance for Loan Losses - Additional Information (Details)	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2020 USD ($) Loan	Sep. 30, 2020 USD ($) Loan Contract	Dec. 31, 2019 USD ($) Contract	Jun. 30, 2020 USD ($)	Aug. 31, 2018 USD ($)
Debt Securities Heldtomaturity Allowance For Credit Loss [Line Items]
Loans Pledged as Collateral	$ 30,100,000	$ 30,100,000	$ 34,600,000
Loans and Leases Receivable, Related Parties, Ending Balance			900,000	$ 400,000
Loans and Leases Receivable, Related Parties, Additions		0	100,000
Loans and Leases Receivable, Related Parties, Proceeds		400	22,000,000
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance, Total					$ 2,900,000
Purchased credit impaired loans					$ 2,800,000
Certain Loans Acquired in Transfer, Accretable Yield	0	0	0
Loans and Leases Receivable, Gross, Total	639,030,000	639,030,000	556,053,000
Non-accruing loans	$ 3,053,000	$ 3,053,000	3,723,000
Percentage of loan balance to Major Franchises	90.00%	90.00%
Loans and Leases Receivable, Nonperforming, Nonaccrual of Interest	$ 3,100,000	$ 3,100,000	3,700,000
Financing Receivable, Troubled Debt Restructuring	100,000	100,000	100,000
Impaired loans with no related allowance recorded, carrying amount	3,547,000	3,547,000	2,861,000
Loans and Leases Receivable, Impaired, Interest Lost on Nonaccrual Loans		124,000	41,000
Interest Income Recorded	36,000	36,000	147,000
Financing Receivable, Restructuring Recorded Investment With Nonaccrual Status	10,000	10,000	16,000
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Cash Flows Expected to be Collected at Acquisition	0	$ 0	$ 0
Financing Receivable, Troubled Debt Restructuring, Subsequent Default, Number of Contracts | Contract		0	0
Loans, allowance for loan losses	7,185,000	$ 7,185,000	$ 5,762,000
Restructured Loan Modified through Extended Maturity and Payment Schedule Modification [Member]
Debt Securities Heldtomaturity Allowance For Credit Loss [Line Items]
Financing Receivable, Restructuring Recorded Investment With Nonaccrual Status	500,000	500,000
Loans, allowance for loan losses	1,000	1,000	1,000
Minimum [Member]
Debt Securities Heldtomaturity Allowance For Credit Loss [Line Items]
Loans Modified in a Troubled Debt Restructuring, Individually Evaluated for Impairment, Principal Balance, Threshold	$ 500,000	$ 500,000
Minimum [Member] | ALC [Member]
Debt Securities Heldtomaturity Allowance For Credit Loss [Line Items]
Loans and Leases Receivable, Nonperforming, Nonaccrual of Interest			50,000
Paycheck Protection Program [Member]
Debt Securities Heldtomaturity Allowance For Credit Loss [Line Items]
Loan, fixed interest rate	1.00%	1.00%
Loan, aggregate principal balance	$ 14,000,000	$ 14,000,000
Number of loans to small businesses | Loan	167	167
Paycheck Protection Program [Member] | Minimum [Member]
Debt Securities Heldtomaturity Allowance For Credit Loss [Line Items]
Loan fee percentage	1.00%	1.00%
Paycheck Protection Program [Member] | Maximum [Member]
Debt Securities Heldtomaturity Allowance For Credit Loss [Line Items]
Loan fee percentage	5.00%	5.00%
Paycheck Protection Program [Member] | Two Year Term Loan [Member]
Debt Securities Heldtomaturity Allowance For Credit Loss [Line Items]
Loan, aggregate principal balance	$ 13,800,000	$ 13,800,000
Loan payment term		two-year
Paycheck Protection Program [Member] | Five Year Term Loan [Member]
Debt Securities Heldtomaturity Allowance For Credit Loss [Line Items]
Loan, aggregate principal balance	200,000	$ 200,000
Loan payment term		five-year
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Debt Securities Heldtomaturity Allowance For Credit Loss [Line Items]
Loans and Leases Receivable, Gross, Total	1,661,000	$ 1,661,000
Financial Asset Acquired With Credit Deterioration [Member]
Debt Securities Heldtomaturity Allowance For Credit Loss [Line Items]
Loans and Leases Receivable, Gross, Total	165,000	165,000
Non-accruing loans	200,000	200,000	200,000
Deffered principal balance of loan reduced	76,800,000
Impaired loans with no related allowance recorded, carrying amount	200,000	200,000	200,000
Financial Asset Acquired With Credit Deterioration [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Debt Securities Heldtomaturity Allowance For Credit Loss [Line Items]
Loans and Leases Receivable, Gross, Total	200,000	200,000	200,000
Financial Asset Acquired With Credit Deterioration [Member] | Substandard [Member]
Debt Securities Heldtomaturity Allowance For Credit Loss [Line Items]
Loans and Leases Receivable, Gross, Total	$ 200,000	$ 200,000	$ 200,000
Real Estate [Member]
Debt Securities Heldtomaturity Allowance For Credit Loss [Line Items]
Percentage of Loan Portfolio	56.90%	56.90%	62.80%

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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