Regulatory Requirements and Restrictions - Capital Amounts and Ratios (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Regulatory requirements
Risk-weighted assets	$ 1,180,000	$ 1,150,000
Total Capital (to Risk-Weighted Assets)
Actual (in Dollars)	$ 170,376	$ 159,525
Actual	14.40%	13.90%
Minimum capital requirements (in Dollars)	$ 94,383	$ 91,695
Minimum capital requirements	8.00%	8.00%
Tier 1 Capital (to Risk-Weighted Assets)
Actual (in Dollars)	$ 155,370	$ 144,819
Actual	13.20%	12.60%
Minimum capital requirements (in Dollars)	$ 70,787	$ 68,772
Minimum capital requirements	6.00%	6.00%
Common Equity Tier 1 Capital (to Risk-Weighted Assets)
Actual (in Dollars)	$ 130,445	$ 120,085
Actual	11.10%	10.50%
Minimum capital requirements (in Dollars)	$ 53,091	$ 51,579
Minimum capital requirements	4.50%	4.50%
Tier 1 Capital (to Average Tangible Assets)
Actual (in Dollars)	$ 155,370	$ 144,819
Actual	10.50%	10.30%
Minimum capital requirements (in Dollars)	$ 59,083	$ 56,463
Minimum capital requirements	4.00%	4.00%
The Bank
Total Capital (to Risk-Weighted Assets)
Actual (in Dollars)	$ 167,657	$ 160,971
Actual	14.20%	14.00%
Minimum capital requirements (in Dollars)	$ 94,163	$ 91,772
Minimum capital requirements	8.00%	8.00%
Minimum to be well capitalized under prompt corrective action provisions (in Dollars)	$ 117,704	$ 114,716
Minimum to be well capitalized under prompt corrective action provisions	10.00%	10.00%
Tier 1 Capital (to Risk-Weighted Assets)
Actual (in Dollars)	$ 152,684	$ 146,307
Actual	13.00%	12.80%
Minimum capital requirements (in Dollars)	$ 70,622	$ 68,829
Minimum capital requirements	6.00%	6.00%
Minimum to be well capitalized under prompt corrective action provisions (in Dollars)	$ 94,163	$ 91,772
Minimum to be well capitalized under prompt corrective action provisions	8.00%	8.00%
Common Equity Tier 1 Capital (to Risk-Weighted Assets)
Actual (in Dollars)	$ 152,684	$ 146,307
Actual	13.00%	12.80%
Minimum capital requirements (in Dollars)	$ 52,967	$ 51,622
Minimum capital requirements	4.50%	4.50%
Minimum to be well capitalized under prompt corrective action provisions (in Dollars)	$ 76,507	$ 74,565
Minimum to be well capitalized under prompt corrective action provisions	6.50%	6.50%
Tier 1 Capital (to Average Tangible Assets)
Actual (in Dollars)	$ 152,684	$ 146,307
Actual	10.40%	10.20%
Minimum capital requirements (in Dollars)	$ 58,934	$ 57,097
Minimum capital requirements	4.00%	4.00%
Minimum to be well capitalized under prompt corrective action provisions (in Dollars)	$ 73,667	$ 71,371
Minimum to be well capitalized under prompt corrective action provisions	5.00%	5.00%