Shareholders' Equity, Compliance with Regulatory Capital Requirements (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Total Capital to Risk Weighted Assets [Abstract]
Actual Amount	$ 342,210	$ 319,983
Current Regulatory Capital Requirement, Amount	$ 209,532	$ 199,981
Total Capital to Risk Weighted Assets, Ratio [Abstract]
Actual Ratio	13.07%	12.80%
Current Regulatory Capital Requirement, Ratio	8.00%	8.00%
Total Common Equity Tier 1 Capital [Abstract]
Actual Amount	$ 299,401	$ 278,981
Current Regulatory Capital Requirement, Amount	$ 117,862	$ 112,489
Total Common Equity Tier 1 Capital, Ratio [Abstract]
Actual Ratio	11.43%	11.16%
Current Regulatory Capital Requirement, Ratio	4.50%	4.50%
Tier 1 Capital to Risk Weighted Assets [Abstract]
Actual Amount	$ 309,250	$ 288,527
Current Regulatory Capital Requirement, Amount	$ 157,150	$ 149,986
Tier 1 Capital to Risk Weighted Assets, Ratio [Abstract]
Actual Ratio	11.81%	11.54%
Current Regulatory Capital Requirement Ratio	6.00%	6.00%
Tier 1 Capital to Average Assets [Abstract]
Actual Amount	$ 309,250	$ 288,527
Current Regulatory Capital Requirement, Amount	$ 123,790	$ 114,568
Tier 1 Capital to Average Assets, Ratio [Abstract]
Actual Ratio	9.99%	10.07%
Current Regulatory Capital Requirement, Ratio	4.00%	4.00%
Bank [Member]
Total Capital to Risk Weighted Assets [Abstract]
Actual Amount	$ 330,041	$ 319,776
Current Regulatory Capital Requirement, Amount	208,552	199,958
Well Capitalized Under Prompt Corrective Action, Amount	$ 260,691	$ 249,947
Total Capital to Risk Weighted Assets, Ratio [Abstract]
Actual Ratio	12.66%	12.79%
Current Regulatory Capital Requirement, Ratio	8.00%	8.00%
Well Capitalized Under Prompt Corrective Action, Ratio	10.00%	10.00%
Total Common Equity Tier 1 Capital [Abstract]
Actual Amount	$ 297,232	$ 288,324
Current Regulatory Capital Requirement, Amount	117,311	112,476
Well Capitalized Under Prompt Corrective Action, Amount	$ 169,449	$ 162,466
Total Common Equity Tier 1 Capital, Ratio [Abstract]
Actual Ratio	11.40%	11.54%
Current Regulatory Capital Requirement, Ratio	4.50%	4.50%
Well Capitalized Under Prompt Corrective Action, Ratio	6.50%	6.50%
Tier 1 Capital to Risk Weighted Assets [Abstract]
Actual Amount	$ 297,232	$ 288,323
Current Regulatory Capital Requirement, Amount	156,414	149,968
Well Capitalized Under Prompt Corrective Action, Amount	$ 208,552	$ 199,958
Tier 1 Capital to Risk Weighted Assets, Ratio [Abstract]
Actual Ratio	11.40%	11.54%
Current Regulatory Capital Requirement Ratio	6.00%	6.00%
Well Capitalized Under Prompt Corrective Action, Ratio	8.00%	8.00%
Tier 1 Capital to Average Assets [Abstract]
Actual Amount	$ 297,232	$ 288,324
Current Regulatory Capital Requirement, Amount	123,178	114,409
Well Capitalized Under Prompt Corrective Action, Amount	$ 153,972	$ 143,011
Tier 1 Capital to Average Assets, Ratio [Abstract]
Actual Ratio	9.65%	10.08%
Current Regulatory Capital Requirement, Ratio	4.00%	4.00%
Well Capitalized Under Prompt Corrective Action, Ratio	5.00%	5.00%