Allowance for loan losses and credit quality Loan Ratings by Class (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	$ 670,244	$ 642,461
Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	497,260	496,721
Satisfactory/Monitor [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	164,374	138,569
Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	8,610	7,171
Residential Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	192,125	187,320
Residential Real Estate [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	174,798	170,416
Residential Real Estate [Member] | Satisfactory/Monitor [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	14,520	14,008
Residential Real Estate [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	2,807	2,896
Construction Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	69,617	55,322
Construction Real Estate [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	47,326	41,141
Construction Real Estate [Member] | Satisfactory/Monitor [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	21,819	14,053
Construction Real Estate [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	472	128
Commercial Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	289,883	276,500
Commercial Real Estate [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	168,654	174,802
Commercial Real Estate [Member] | Satisfactory/Monitor [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	117,004	98,327
Commercial Real Estate [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	4,225	3,371
Commercial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	47,699	47,228
Commercial [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	35,625	34,303
Commercial [Member] | Satisfactory/Monitor [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	10,974	12,150
Commercial [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	1,100	775
Consumer [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	3,562	3,241
Consumer [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	3,499	3,209
Consumer [Member] | Satisfactory/Monitor [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	57	31
Consumer [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	6	1
Municipal [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	67,358	72,850
Municipal [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	67,358	72,850
Municipal [Member] | Satisfactory/Monitor [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Municipal [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	$ 0	$ 0