Allowance for loan losses and credit quality Allocation of Investment in Loans, by Impairment Methodology (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually evaluated for impairment	$ 4,031	$ 5,296
Collectively evaluated for impairment	532,169	527,994
Loans	536,200	533,290
Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually evaluated for impairment	1,770	1,448
Collectively evaluated for impairment	173,552	171,279
Loans	175,322	172,727
Construction Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually evaluated for impairment	85	88
Collectively evaluated for impairment	40,650	34,101
Loans	40,735	34,189
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually evaluated for impairment	1,768	3,328
Collectively evaluated for impairment	250,586	245,735
Loans	252,354	249,063
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually evaluated for impairment	408	432
Collectively evaluated for impairment	46,190	41,567
Loans	46,598	41,999
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	3,537	3,962
Loans	3,537	3,962
Municipal [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	17,654	31,350
Loans	$ 17,654	$ 31,350

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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- Definition

The balance of financing receivables that were collectively evaluated for impairment.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (h)
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953423-111524

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- Definition

The balance of financing receivables that were individually evaluated for impairment.

+ References

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- Definition

Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=65884687&loc=d3e4428-111522

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