Loans - Credit exposure (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment [Line Items]
Total Loans	$ 1,164,821	$ 1,005,525
Threshold limit to consider loan as nonperforming	90 days
Commercial
Financing Receivable, Recorded Investment [Line Items]
Total Loans	$ 208,717	177,481
Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans	625,218	503,154
Commercial real estate | Construction and land development
Financing Receivable, Recorded Investment [Line Items]
Total Loans	114,258	72,968
Commercial real estate | Other
Financing Receivable, Recorded Investment [Line Items]
Total Loans	510,960	430,186
Commercial real estate | Real estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans	510,960	430,186
Residential
Financing Receivable, Recorded Investment [Line Items]
Total Loans	325,855	318,883
Residential | Real estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans	215,104	220,434
Residential | Home equity
Financing Receivable, Recorded Investment [Line Items]
Total Loans	110,751	98,449
Consumer
Financing Receivable, Recorded Investment [Line Items]
Total Loans	5,031	6,007
Consumer | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	5,003	5,999
Consumer | Nonperforming [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Loans	28	8
Pass | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total Loans	208,098	175,963
Pass | Commercial real estate | Construction and land development
Financing Receivable, Recorded Investment [Line Items]
Total Loans	112,729	68,853
Pass | Commercial real estate | Other
Financing Receivable, Recorded Investment [Line Items]
Total Loans	501,081	418,719
Pass | Residential | Real estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans	199,278	200,008
Pass | Residential | Home equity
Financing Receivable, Recorded Investment [Line Items]
Total Loans	108,799	96,142
Special Mention | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total Loans	592	1,364
Special Mention | Commercial real estate | Construction and land development
Financing Receivable, Recorded Investment [Line Items]
Total Loans	902	1,210
Special Mention | Commercial real estate | Other
Financing Receivable, Recorded Investment [Line Items]
Total Loans	4,859	5,860
Special Mention | Residential | Real estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans	10,600	14,638
Special Mention | Residential | Home equity
Financing Receivable, Recorded Investment [Line Items]
Total Loans	1,257	1,314
Substandard | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total Loans	27	154
Substandard | Commercial real estate | Construction and land development
Financing Receivable, Recorded Investment [Line Items]
Total Loans	627	2,905
Substandard | Commercial real estate | Other
Financing Receivable, Recorded Investment [Line Items]
Total Loans	5,020	5,607
Substandard | Residential | Real estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans	5,226	5,788
Substandard | Residential | Home equity
Financing Receivable, Recorded Investment [Line Items]
Total Loans	695	993
Doubtful | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total Loans	0	0
Doubtful | Commercial real estate | Construction and land development
Financing Receivable, Recorded Investment [Line Items]
Total Loans	0	0
Doubtful | Commercial real estate | Other
Financing Receivable, Recorded Investment [Line Items]
Total Loans	0	0
Doubtful | Residential | Real estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans	0	0
Doubtful | Residential | Home equity
Financing Receivable, Recorded Investment [Line Items]
Total Loans	$ 0	$ 0