Regulatory Matters - The Company's Consolidated Capital Ratios and the Bank's Actual Capital Amounts and Ratios (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 leverage capital to adjusted total assets, Actual Amount	$ 96,428	$ 92,803
Tier 1 leverage capital to adjusted total assets, Minimum Capital Required - Basel III Phase-In Schedule, Amount	36,273	34,392
Tier 1 leverage capital to adjusted total assets, To be Well Capitalized for Prompt Corrective Action Provision, Amount	45,341	42,990
Total capital to risk weighted assets, Actual Amount	101,228	98,915
Total capital to risk weighted assets, Minimum Capital Required - Basel III Phase-In Schedule, Amount	57,354	52,682
Total capital to risk weighted assets, To be Well Capitalized for Prompt Corrective Action Provision, Amount	62,005	61,080
Tier 1 capital to risk weighted assets, Actual Amount	96,428	92,803
Tier 1 capital to risk weighted assets, Minimum Capital Required - Basel III Phase-In Schedule, Amount	44,953	40,466
Tier 1 capital to risk weighted assets, To be Well Capitalized for Prompt Corrective Action Provision, Amount	49,604	48,864
Common equity tier 1 capital to risk weighted assets, Actual Amount	96,428	92,803
Common equity tier 1 capital to risk weighted assets, Minimum Capital Required - Basel III Phase-In Schedule, Amount	$ 35,653	$ 31,304
Tier 1 leverage capital to adjusted total assets, Actual Ratio	10.90%	10.80%
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	16.30%	16.20%
Total capital to risk weighted assets, Minimum Capital Required - Basel III Phase-In Schedule, Ratio	9.25%	8.625%
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	15.60%	15.20%
Tier 1 capital to risk weighted assets, Minimum Capital Required - Basel III Phase-In Schedule, Ratio	7.25%	6.625%
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	15.60%	15.20%
Common equity tier 1 capital to risk weighted assets, Minimum Capital Required - Basel III Phase-In Schedule, Ratio	5.75%	5.125%
Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 leverage capital to adjusted total assets, Actual Amount	$ 94,196	$ 91,617
Tier 1 leverage capital to adjusted total assets, Minimum Capital Required - Basel III Phase-In Schedule, Amount	35,461	34,315
Tier 1 leverage capital to adjusted total assets, To be Well Capitalized for Prompt Corrective Action Provision, Amount	44,326	42,894
Total capital to risk weighted assets, Actual Amount	98,995	97,729
Total capital to risk weighted assets, Minimum Capital Required - Basel III Phase-In Schedule, Amount	57,225	52,561
Total capital to risk weighted assets, To be Well Capitalized for Prompt Corrective Action Provision, Amount	61,865	60,941
Tier 1 capital to risk weighted assets, Actual Amount	94,196	91,617
Tier 1 capital to risk weighted assets, Minimum Capital Required - Basel III Phase-In Schedule, Amount	44,852	40,373
Tier 1 capital to risk weighted assets, To be Well Capitalized for Prompt Corrective Action Provision, Amount	49,492	48,753
Common equity tier 1 capital to risk weighted assets, Actual Amount	94,196	91,617
Common equity tier 1 capital to risk weighted assets, Minimum Capital Required - Basel III Phase-In Schedule, Amount	35,573	31,232
Common equity tier 1 capital to risk weighted assets, To be Well Capitalized for Prompt Corrective Action Provision, Amount	$ 40,213	$ 39,611
Tier 1 leverage capital to adjusted total assets, Actual Ratio	10.60%	10.70%
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	16.00%	16.00%
Total capital to risk weighted assets, Minimum Capital Required - Basel III Phase-In Schedule, Ratio	9.25%	8.625%
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%	15.00%
Tier 1 capital to risk weighted assets, Minimum Capital Required - Basel III Phase-In Schedule, Ratio	7.25%	6.625%
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%	15.00%
Common equity tier 1 capital to risk weighted assets, Minimum Capital Required - Basel III Phase-In Schedule, Ratio	5.75%	5.125%
Common equity tier 1 capital to risk weighted assets, To be Well Capitalized for Prompt Corrective Action Provision, Ratio	6.50%	6.50%