Allowance for loan losses and credit quality Troubled Debt Restructured Loans (Details) $ in Thousands	Dec. 31, 2019 USD ($) loans	Dec. 31, 2018 USD ($) loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled Debt Restructured Loans, Number of Loans \| loans	40	42
Troubled Debt Restructured Loans, Principal Balance \| $	$ 2,871	$ 3,309
Residential Real Estate [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled Debt Restructured Loans, Number of Loans \| loans	25	27
Troubled Debt Restructured Loans, Principal Balance \| $	$ 1,515	$ 1,678
Construction Real Estate [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled Debt Restructured Loans, Number of Loans \| loans	2	2
Troubled Debt Restructured Loans, Principal Balance \| $	$ 100	$ 119
Commercial Real Estate [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled Debt Restructured Loans, Number of Loans \| loans	8	9
Troubled Debt Restructured Loans, Principal Balance \| $	$ 966	$ 1,172
Commercial [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled Debt Restructured Loans, Number of Loans \| loans	5	4
Troubled Debt Restructured Loans, Principal Balance \| $	$ 290	$ 340

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Number of financing receivables that have been modified by troubled debt restructurings.

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Amount of financing receivable modified as troubled debt restructuring.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953676-111524

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=118939409&loc=d3e18845-111554

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