Allowance for loan losses and credit quality Loan Ratings by Class (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	$ 676,531	$ 670,244
Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	495,857	497,260
Satisfactory/Monitor [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	172,622	164,374
Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	8,052	8,610
Residential Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	190,420	192,125
Residential Real Estate [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	172,425	174,798
Residential Real Estate [Member] | Satisfactory/Monitor [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	15,078	14,520
Residential Real Estate [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	2,917	2,807
Construction Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	54,207	69,617
Construction Real Estate [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	33,632	47,326
Construction Real Estate [Member] | Satisfactory/Monitor [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	20,091	21,819
Construction Real Estate [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	484	472
Commercial Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	304,204	289,883
Commercial Real Estate [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	174,365	168,654
Commercial Real Estate [Member] | Satisfactory/Monitor [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	125,767	117,004
Commercial Real Estate [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	4,072	4,225
Commercial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	47,633	47,699
Commercial [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	35,464	35,625
Commercial [Member] | Satisfactory/Monitor [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	11,595	10,974
Commercial [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	574	1,100
Consumer [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	3,460	3,562
Consumer [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	3,364	3,499
Consumer [Member] | Satisfactory/Monitor [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	91	57
Consumer [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	5	6
Municipal [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	76,607	67,358
Municipal [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	76,607	67,358
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