| **Loans - Past-due Status of Loans by Class (Details) - USD ($) $ in Thousands** | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 |
|----------------------------------------------------------------------------------|---------------|---------------|---------------|
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                 |          |          |          |
| Past Due                                                                         | $ 12,658      | $ 8,287       |          |
| Current                                                                          | 1,058,868     | 980,351       |          |
| Loans                                                                            | 1,071,526     | 988,638       | $ 917,564     |
| 90 Plus Days And Accruing                                                        | 777           | 136           |          |
| Commercial | Real Estate                                                         |          |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                 |          |          |          |
| Past Due                                                                         | 3,476         | 884           |          |
| Current                                                                          | 299,030       | 268,578       |          |
| Loans                                                                            | 302,506       | 269,462       | 242,311       |
| 90 Plus Days And Accruing                                                        | 753           | 0             |          |
| Commercial | Construction                                                        |          |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                 |          |          |          |
| Past Due                                                                         | 0             | 273           |          |
| Current                                                                          | 25,406        | 24,608        |          |
| Loans                                                                            | 25,406        | 24,881        | 30,932        |
| 90 Plus Days And Accruing                                                        | 0             | 0             |          |
| Commercial | Other                                                               |          |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                 |          |          |          |
| Past Due                                                                         | 1,031         | 328           |          |
| Current                                                                          | 149,738       | 128,013       |          |
| Loans                                                                            | 150,769       | 128,341       | 104,531       |
| 90 Plus Days And Accruing                                                        | 20            | 25            |          |
| Municipal                                                                        |          |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                 |          |          |          |
| Past Due                                                                         | 0             | 0             |          |
| Current                                                                          | 27,056        | 19,751        |          |
| Loans                                                                            | 27,056        | 19,751        | 20,424        |
| 90 Plus Days And Accruing                                                        | 0             | 0             |          |
| Residential | Construction                                                       |          |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                 |          |          |          |
| Past Due                                                                         | 0             | 368           |          |
| Current                                                                          | 18,303        | 8,083         |          |
| Loans                                                                            | 18,303        | 8,451         | 12,160        |
| 90 Plus Days And Accruing                                                        | 0             | 0             |          |
| Residential | Term                                                               |          |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                 |          |          |          |
| Past Due                                                                         | 6,403         | 5,187         |          |
| Current                                                                          | 405,066       | 397,843       |          |
| Loans                                                                            | 411,469       | 403,030       | 384,032       |
| 90 Plus Days And Accruing                                                        | 0             | 100           |          |
| Home Equity LIne of Credit                                                       |          |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                 |          |          |          |
| Past Due                                                                         | 1,564         | 1,108         |          |
| Current                                                                          | 109,343       | 109,094       |          |
| Loans                                                                            | 110,907       | 110,202       | 103,521       |
| 90 Plus Days And Accruing                                                        | 0             | 0             |          |
| Consumer                                                                         |          |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                 |          |          |          |
| Past Due                                                                         | 184           | 139           |          |
| Current                                                                          | 24,926        | 24,381        |          |
| Loans                                                                            | 25,110        | 24,520        | $ 19,653      |
| 90 Plus Days And Accruing                                                        | 4             | 11            |          |
| 30-59 Days Past Due                                                              |          |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                 |          |          |          |
| Past Due                                                                         | 2,711         | 2,122         |          |
| 30-59 Days Past Due | Commercial | Real Estate                                   |          |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                 |          |          |          |
| Past Due                                                                         | 1,039         | 603           |          |
| 30-59 Days Past Due | Commercial | Construction                                  |          |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                 |          |          |          |
| Past Due                                                                         | 0             | 35            |          |
| 30-59 Days Past Due | Commercial | Other                                         |          |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                 |          |          |          |
| Past Due                                                                         | 202           | 303           |          |
| 30-59 Days Past Due | Municipal                                                  |          |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                 |          |          |          |
| Past Due                                                                         | 0             | 0             |          |
| 30-59 Days Past Due | Residential | Construction                                 |          |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                 |          |          |          |
| Past Due                                                                         | 0             | 368           |          |
| 30-59 Days Past Due | Residential | Term                                         |          |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                 |          |          |          |
| Past Due                                                                         | 631           | 450           |          |
| 30-59 Days Past Due | Home Equity LIne of Credit                                 |          |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                 |          |          |          |
| Past Due                                                                         | 704           | 261           |          |
| 30-59 Days Past Due | Consumer                                                   |          |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                 |          |          |          |
| Past Due                                                                         | 135           | 102           |          |
| 60-89 Days Past Due                                                              |          |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                 |          |          |          |
| Past Due                                                                         | 4,227         | 2,379         |          |
| 60-89 Days Past Due | Commercial | Real Estate                                   |          |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                 |          |          |          |
| Past Due                                                                         | 22            | 0             |          |
| 60-89 Days Past Due | Commercial | Construction                                  |          |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                 |          |          |          |
| Past Due                                                                         | 0             | 0             |          |
| 60-89 Days Past Due | Commercial | Other                                         |          |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                 |          |          |          |
| Past Due                                                                         | 33            | 0             |          |
| 60-89 Days Past Due | Municipal                                                  |          |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                 |          |          |          |
| Past Due                                                                         | 0             | 0             |          |
| 60-89 Days Past Due | Residential | Construction                                 |          |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                 |          |          |          |
| Past Due                                                                         | 0             | 0             |          |
| 60-89 Days Past Due | Residential | Term                                         |          |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                 |          |          |          |
| Past Due                                                                         | 3,970         | 2,098         |          |
| 60-89 Days Past Due | Home Equity LIne of Credit                                 |          |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                 |          |          |          |
| Past Due                                                                         | 157           | 255           |          |
| 60-89 Days Past Due | Consumer                                                   |          |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                 |          |          |          |
| Past Due                                                                         | 45            | 26            |          |
| 90 Days Past Due                                                                 |          |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                 |          |          |          |
| Past Due                                                                         | 5,720         | 3,786         |          |
| 90 Days Past Due | Commercial | Real Estate                                      |          |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                 |          |          |          |
| Past Due                                                                         | 2,415         | 281           |          |
| 90 Days Past Due | Commercial | Construction                                     |          |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                 |          |          |          |
| Past Due                                                                         | 0             | 238           |          |
| 90 Days Past Due | Commercial | Other                                            |          |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                 |          |          |          |
| Past Due                                                                         | 796           | 25            |          |
| 90 Days Past Due | Municipal                                                     |          |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                 |          |          |          |
| Past Due                                                                         | 0             | 0             |          |
| 90 Days Past Due | Residential | Construction                                    |          |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                 |          |          |          |
| Past Due                                                                         | 0             | 0             |          |
| 90 Days Past Due | Residential | Term                                            |          |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                 |          |          |          |
| Past Due                                                                         | 1,802         | 2,639         |          |
| 90 Days Past Due | Home Equity LIne of Credit                                    |          |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                 |          |          |          |
| Past Due                                                                         | 703           | 592           |          |
| 90 Days Past Due | Consumer                                                      |          |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                 |          |          |          |
| Past Due                                                                         | $ 4           | $ 11          |          |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
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.
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Recorded investment in financing receivables that are 90 days or more past due and still accruing.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Recorded Investment -URI http://asc.fasb.org/extlink&oid=65880944Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 7 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=66008989&loc=d3e5111-111524
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Financing receivables that are current.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 7A -URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953401-111524
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Recorded Investment in financing receivables that are past due at the balance sheet date.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Recorded Investment -URI http://asc.fasb.org/extlink&oid=65880944Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 7A -URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953401-111524
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. 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=d3e4428-111522Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=66008989&loc=d3e5074-111524
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