Regulatory Matters - The Company's Consolidated Capital Ratios and the Bank's Actual Capital Amounts and Ratios (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 leverage capital to adjusted total assets, Actual Amount	$ 98,532	$ 95,709
Tier 1 leverage capital to adjusted total assets, Minimum Capital Required - Basel III Phase-In Schedule, Amount	36,161	36,137
Tier 1 leverage capital to adjusted total assets, To be Well Capitalized for Prompt Corrective Action Provision, Amount	45,201	45,171
Total capital to risk weighted assets, Actual Amount	103,085	100,535
Total capital to risk weighted assets, Minimum Capital Required - Basel III Phase-In Schedule, Amount	51,750	50,352
Total capital to risk weighted assets, To be Well Capitalized for Prompt Corrective Action Provision, Amount	64,688	62,940
Tier 1 capital to risk weighted assets, Actual Amount	98,532	95,709
Tier 1 capital to risk weighted assets, Minimum Capital Required - Basel III Phase-In Schedule, Amount	38,813	37,764
Tier 1 capital to risk weighted assets, To be Well Capitalized for Prompt Corrective Action Provision, Amount	51,750	50,352
Common equity tier 1 capital to risk weighted assets, Actual Amount	98,532	95,709
Common equity tier 1 capital to risk weighted assets, Minimum Capital Required - Basel III Phase-In Schedule, Amount	$ 29,110	$ 28,323
Tier 1 leverage capital to adjusted total assets, Actual Ratio	10.90%	10.60%
Tier 1 leverage capital to adjusted total assets, Minimum Capital Required - Basel III Phase-In Schedule, Ratio	4.00%	4.00%
Tier 1 leverage capital to adjusted total assets, To be Well Capitalized for Prompt Corrective Action Provision, Ratio	5.00%	5.00%
Total capital to risk weighted assets, Actual Ratio	15.90%	16.00%
Total capital to risk weighted assets, Minimum Capital Required - Basel III Phase-In Schedule, Ratio	8.00%	8.00%
Total capital to risk weighted assets, To be Well Capitalized for Prompt Corrective Action Provision, Ratio	10.00%	10.00%
Tier 1 capital to risk weighted assets, Actual Ratio	15.20%	15.20%
Tier 1 capital to risk weighted assets, Minimum Capital Required - Basel III Phase-In Schedule, Ratio	6.00%	6.00%
Tier 1 capital to risk weighted assets, To be Well Capitalized for Prompt Corrective Action Provision, Ratio	8.00%	8.00%
Common equity tier 1 capital to risk weighted assets, Actual Ratio	15.20%	15.20%
Common equity tier 1 capital to risk weighted assets, Minimum Capital Required - Basel III Phase-In Schedule, Ratio	4.50%	4.50%
Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 leverage capital to adjusted total assets, Actual Amount	$ 97,110	$ 95,123
Tier 1 leverage capital to adjusted total assets, Minimum Capital Required - Basel III Phase-In Schedule, Amount	36,115	36,090
Tier 1 leverage capital to adjusted total assets, To be Well Capitalized for Prompt Corrective Action Provision, Amount	45,143	45,112
Total capital to risk weighted assets, Actual Amount	101,663	99,949
Total capital to risk weighted assets, Minimum Capital Required - Basel III Phase-In Schedule, Amount	51,639	50,314
Total capital to risk weighted assets, To be Well Capitalized for Prompt Corrective Action Provision, Amount	64,549	62,892
Tier 1 capital to risk weighted assets, Actual Amount	97,110	95,123
Tier 1 capital to risk weighted assets, Minimum Capital Required - Basel III Phase-In Schedule, Amount	38,729	37,735
Tier 1 capital to risk weighted assets, To be Well Capitalized for Prompt Corrective Action Provision, Amount	51,639	50,314
Common equity tier 1 capital to risk weighted assets, Actual Amount	97,110	95,123
Common equity tier 1 capital to risk weighted assets, Minimum Capital Required - Basel III Phase-In Schedule, Amount	29,047	28,301
Common equity tier 1 capital to risk weighted assets, To be Well Capitalized for Prompt Corrective Action Provision, Amount	$ 42,207	$ 40,880
Tier 1 leverage capital to adjusted total assets, Actual Ratio	10.80%	10.50%
Tier 1 leverage capital to adjusted total assets, Minimum Capital Required - Basel III Phase-In Schedule, Ratio	4.00%	4.00%
Tier 1 leverage capital to adjusted total assets, To be Well Capitalized for Prompt Corrective Action Provision, Ratio	5.00%	5.00%
Total capital to risk weighted assets, Actual Ratio	15.80%	15.90%
Total capital to risk weighted assets, Minimum Capital Required - Basel III Phase-In Schedule, Ratio	8.00%	8.00%
Total capital to risk weighted assets, To be Well Capitalized for Prompt Corrective Action Provision, Ratio	10.00%	10.00%
Tier 1 capital to risk weighted assets, Actual Ratio	15.00%	15.10%
Tier 1 capital to risk weighted assets, Minimum Capital Required - Basel III Phase-In Schedule, Ratio	6.00%	6.00%
Tier 1 capital to risk weighted assets, To be Well Capitalized for Prompt Corrective Action Provision, Ratio	8.00%	8.00%
Common equity tier 1 capital to risk weighted assets, Actual Ratio	15.00%	15.10%
Common equity tier 1 capital to risk weighted assets, Minimum Capital Required - Basel III Phase-In Schedule, Ratio	4.50%	4.50%
Common equity tier 1 capital to risk weighted assets, To be Well Capitalized for Prompt Corrective Action Provision, Ratio	6.50%	6.50%