Allowance for loan losses and credit quality Loan Ratings by Class (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	$ 766,050	$ 670,244
Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	576,866	497,260
Satisfactory/Monitor
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	180,979	164,374
Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	8,205	8,610
Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	182,935	192,125
Residential real estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	164,691	174,798
Residential real estate | Satisfactory/Monitor
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	15,003	14,520
Residential real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	3,241	2,807
Construction real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	49,668	69,617
Construction real estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	36,439	47,326
Construction real estate | Satisfactory/Monitor
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	12,696	21,819
Construction real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	533	472
Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	317,985	289,883
Commercial real estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	173,011	168,654
Commercial real estate | Satisfactory/Monitor
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	141,017	117,004
Commercial real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	3,957	4,225
Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	114,868	47,699
Commercial | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	102,144	35,625
Commercial | Satisfactory/Monitor
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	12,251	10,974
Commercial | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	473	1,100
Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	2,833	3,562
Consumer | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	2,820	3,499
Consumer | Satisfactory/Monitor
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	12	57
Consumer | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	1	6
Municipal
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	97,761	67,358
Municipal | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	97,761	67,358
Municipal | Satisfactory/Monitor
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Municipal | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	$ 0	$ 0