Loans - Balance in the Allowance for Loan Losses and the Recorded Investment in Loans by Portfolio Segment, Based on the Impairment Method (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Balance in the Allowance for Loan Losses and the Recorded Investment in Loans by Portfolio Segment, Based on the Impairment Method
Allowance for loan losses, Individually evaluated for impairment	$ 290	$ 329
Allowance for loan losses, Collectively evaluated for impairment	19,368	18,760
Total allowance balance	19,658	19,089	$ 18,926	$ 18,379
Loans, Individually evaluated for impairment	2,774	2,945
Loans, Collectively evaluated for impairment	1,580,403	1,500,177
Loans, Acquired with deteriorated credit quality		245
Loans and Leases Receivable, Gross	1,583,177	1,503,367
Commercial
Balance in the Allowance for Loan Losses and the Recorded Investment in Loans by Portfolio Segment, Based on the Impairment Method
Allowance for loan losses, Individually evaluated for impairment	290	329
Allowance for loan losses, Collectively evaluated for impairment	10,318	10,327
Total allowance balance	10,608	10,656	10,748	11,187
Loans, Individually evaluated for impairment	1,775	2,057
Loans, Collectively evaluated for impairment	571,521	602,029
Loans, Acquired with deteriorated credit quality		245
Loans and Leases Receivable, Gross	573,296	604,331
Real estate
Balance in the Allowance for Loan Losses and the Recorded Investment in Loans by Portfolio Segment, Based on the Impairment Method
Allowance for loan losses, Collectively evaluated for impairment	8,950	8,327
Total allowance balance	8,950	8,327	8,076	7,070
Loans, Individually evaluated for impairment	998	885
Loans, Collectively evaluated for impairment	996,488	877,691
Loans and Leases Receivable, Gross	997,486	878,576
Consumer
Balance in the Allowance for Loan Losses and the Recorded Investment in Loans by Portfolio Segment, Based on the Impairment Method
Allowance for loan losses, Collectively evaluated for impairment	100	106
Total allowance balance	100	106	$ 102	$ 122
Loans, Individually evaluated for impairment	1	3
Loans, Collectively evaluated for impairment	12,394	20,457
Loans and Leases Receivable, Gross	$ 12,395	$ 20,460

The recorded balance, net of any applicable reductions (for example, unamortized accretable yield and allowance for loan losses). This relates to loans not accounted for 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.

Reference 1: 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=82894903&loc=d3e15032-111544

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=82894507&loc=d3e13503-111538

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The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

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Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

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

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

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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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.

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