Loans - Receivables Past Due (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Analysis by portfolio segment of the entity's past due loans [Abstract]
Total Past Due	$ 3,274	$ 5,438
90 Days Past Due and Still Accruing	359	587
Non- Accrual Loans	2,201	2,965
Current	1,332,851	1,159,383
Total Loans	1,336,125	1,164,821
Commercial
Analysis by portfolio segment of the entity's past due loans [Abstract]
Total Past Due	182	69
90 Days Past Due and Still Accruing	0	0
Non- Accrual Loans	90	19
Current	251,484	208,648
Total Loans	251,666	208,717
Commercial real estate
Analysis by portfolio segment of the entity's past due loans [Abstract]
Total Loans	760,848	625,218
Commercial real estate | Construction and land development
Analysis by portfolio segment of the entity's past due loans [Abstract]
Total Past Due	36	136
90 Days Past Due and Still Accruing	0	0
Non- Accrual Loans	36	64
Current	123,111	114,122
Total Loans	123,147	114,258
Commercial real estate | Real estate
Analysis by portfolio segment of the entity's past due loans [Abstract]
Total Past Due	855	1,239
90 Days Past Due and Still Accruing	280	339
Non- Accrual Loans	489	773
Current	636,846	509,721
Total Loans	637,701	510,960
Residential
Analysis by portfolio segment of the entity's past due loans [Abstract]
Total Loans	319,183	325,855
Residential | Real estate
Analysis by portfolio segment of the entity's past due loans [Abstract]
Total Past Due	1,775	3,447
90 Days Past Due and Still Accruing	79	248
Non- Accrual Loans	1,343	1,802
Current	207,551	211,657
Total Loans	209,326	215,104
Residential | Home equity
Analysis by portfolio segment of the entity's past due loans [Abstract]
Total Past Due	400	518
90 Days Past Due and Still Accruing	0	0
Non- Accrual Loans	243	289
Current	109,457	110,233
Total Loans	109,857	110,751
Consumer
Analysis by portfolio segment of the entity's past due loans [Abstract]
Total Past Due	26	29
90 Days Past Due and Still Accruing	0	0
Non- Accrual Loans	0	18
Current	4,402	5,002
Total Loans	4,428	5,031
30- 59 Days Past Due
Analysis by portfolio segment of the entity's past due loans [Abstract]
Total Past Due	622	1,625
30- 59 Days Past Due | Commercial
Analysis by portfolio segment of the entity's past due loans [Abstract]
Total Past Due	92	50
30- 59 Days Past Due | Commercial real estate | Construction and land development
Analysis by portfolio segment of the entity's past due loans [Abstract]
Total Past Due	0	60
30- 59 Days Past Due | Commercial real estate | Real estate
Analysis by portfolio segment of the entity's past due loans [Abstract]
Total Past Due	86	0
30- 59 Days Past Due | Residential | Real estate
Analysis by portfolio segment of the entity's past due loans [Abstract]
Total Past Due	282	1,280
30- 59 Days Past Due | Residential | Home equity
Analysis by portfolio segment of the entity's past due loans [Abstract]
Total Past Due	141	229
30- 59 Days Past Due | Consumer
Analysis by portfolio segment of the entity's past due loans [Abstract]
Total Past Due	21	6
60-89 Days Past Due
Analysis by portfolio segment of the entity's past due loans [Abstract]
Total Past Due	92	261
60-89 Days Past Due | Commercial
Analysis by portfolio segment of the entity's past due loans [Abstract]
Total Past Due	0	0
60-89 Days Past Due | Commercial real estate | Construction and land development
Analysis by portfolio segment of the entity's past due loans [Abstract]
Total Past Due	0	12
60-89 Days Past Due | Commercial real estate | Real estate
Analysis by portfolio segment of the entity's past due loans [Abstract]
Total Past Due	0	127
60-89 Days Past Due | Residential | Real estate
Analysis by portfolio segment of the entity's past due loans [Abstract]
Total Past Due	71	117
60-89 Days Past Due | Residential | Home equity
Analysis by portfolio segment of the entity's past due loans [Abstract]
Total Past Due	16	0
60-89 Days Past Due | Consumer
Analysis by portfolio segment of the entity's past due loans [Abstract]
Total Past Due	$ 5	$ 5