Allowance for loan losses and credit quality Loan Ratings by Class (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment [Line Items]
Loans Not Acquired	$ 500,506	$ 470,926
Acquired loans	0	9,052
Loans	500,506	479,978
Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	422,391	396,303
Satisfactory and Monitor [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	68,487	66,012
Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	9,628	8,611
Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans Not Acquired	165,396	160,838
Acquired loans	0	4,637
Loans	165,396	165,475
Residential Real Estate [Member] \| Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	150,535	141,259
Residential Real Estate [Member] \| Satisfactory and Monitor [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	11,329	17,483
Residential Real Estate [Member] \| Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	3,532	2,096
Construction Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans Not Acquired	42,889	37,258
Acquired loans	0	0
Loans	42,889	37,258
Construction Real Estate [Member] \| Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	37,750	31,519
Construction Real Estate [Member] \| Satisfactory and Monitor [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	4,968	5,347
Construction Real Estate [Member] \| Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	171	392
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans Not Acquired	230,442	207,295
Acquired loans	0	4,415
Loans	230,442	211,710
Commercial Real Estate [Member] \| Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	175,438	159,725
Commercial Real Estate [Member] \| Satisfactory and Monitor [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	49,745	41,728
Commercial Real Estate [Member] \| Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	5,259	5,842
Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans Not Acquired	21,397	20,620
Acquired loans	0	0
Loans	21,397	20,620
Commercial [Member] \| Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	18,347	18,960
Commercial [Member] \| Satisfactory and Monitor [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	2,384	1,384
Commercial [Member] \| Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	666	276
Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans Not Acquired	3,963	4,435
Acquired loans	0	0
Loans	3,963	4,435
Consumer [Member] \| Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	3,902	4,360
Consumer [Member] \| Satisfactory and Monitor [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	61	70
Consumer [Member] \| Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	0	5
Municipal [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans Not Acquired	36,419	40,480
Acquired loans	0	0
Loans	36,419	40,480
Municipal [Member] \| Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	36,419	40,480
Municipal [Member] \| Satisfactory and Monitor [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	0	0
Municipal [Member] \| Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	$ 0	$ 0

Reflects the aggregate gross carrying amount of all categories of loans and leases held in portfolio, the total of which does not include loans acquired in transfer not accounted for as debt securities. Amount is prior to deducting deferred income and the allowance for losses on loans and leases.

No definition available.

+ Details

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- Definition

The undiscounted sum of all amounts, including amounts deemed principal, interest, fees, penalties, and other under the loan, owed to the investor at the reporting date, whether or not currently due and whether or not any such amounts have been written or charged off by the investor. This relates to loans not accounted for as debt securities, with evidence of deterioration of credit quality since origination that were acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 15
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=27045933&loc=d3e13503-111538

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=6379141&loc=d3e15032-111544

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- Definition

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+ References

No definition available.

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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=28367877&loc=d3e4428-111522

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