Minimum Regulatory Capital Requirements - Summary of Actual and Minimum Capital Amounts and Ratios (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]
Total capital (to risk weighted assets), actual amount	$ 84,565	$ 35,242
Tier 1 capital (to risk weighted assets), actual amount	81,294	32,198
Common equity Tier 1 capital (to risk weighted assets), actual amount	81,294	32,198
Tier 1 capital (to average assets), actual amount	$ 81,294	$ 32,198
Total capital (to risk weighted assets), actual ratio	28.50%	14.50%
Tier 1 capital (to risk weighted assets), actual ratio	27.40%	13.20%
Common equity Tier 1 capital (to risk weighted assets), actual ratio	27.40%	13.20%
Tier 1 capital (to average assets), actual ratio	16.90%	8.40%
Total capital (to risk weighted assets), for minimum capital adequacy purposes amount	$ 23,762	$ 19,465
Tier 1 capital (to risk weighted assets), for minimum capital adequacy purposes amount	17,822	14,599
Common equity Tier 1 capital (to risk weighted assets), for minimum capital adequacy amount	13,366	10,949
Common equity Tier 1 capital (to risk weighted assets), for minimum capital adequacy amount	$ 19,277	$ 15,382
Total capital (to risk weighted assets), for minimum capital adequacy purposes ratio	8.00%	8.00%
Tier 1 capital (to risk weighted assets), for minimum capital adequacy purposes ratio	6.00%	6.00%
Common equity Tier 1 capital (to risk weighted assets), for minimum capital adequacy purposes ratio	4.50%	4.50%
Tier 1 capital (to average assets), for minimum capital adequacy purposes ratio	4.00%	4.00%
Bank [Member]
Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]
Total capital (to risk weighted assets), actual amount	$ 73,991	$ 35,142
Tier 1 capital (to risk weighted assets), actual amount	70,720	32,098
Common equity Tier 1 capital (to risk weighted assets), actual amount	70,720	32,098
Tier 1 capital (to average assets), actual amount	$ 70,720	$ 32,098
Total capital (to risk weighted assets), actual ratio	24.90%	14.40%
Tier 1 capital (to risk weighted assets), actual ratio	23.80%	13.20%
Common equity Tier 1 capital (to risk weighted assets), actual ratio	23.80%	13.20%
Tier 1 capital (to average assets), actual ratio	14.70%	8.30%
Total capital (to risk weighted assets), for minimum capital adequacy purposes amount	$ 23,763	$ 19,465
Tier 1 capital (to risk weighted assets), for minimum capital adequacy purposes amount	17,822	14,599
Common equity Tier 1 capital (to risk weighted assets), for minimum capital adequacy amount	13,366	10,949
Common equity Tier 1 capital (to risk weighted assets), for minimum capital adequacy amount	$ 19,277	$ 15,382
Total capital (to risk weighted assets), for minimum capital adequacy purposes ratio	8.00%	8.00%
Tier 1 capital (to risk weighted assets), for minimum capital adequacy purposes ratio	6.00%	6.00%
Common equity Tier 1 capital (to risk weighted assets), for minimum capital adequacy purposes ratio	4.50%	4.50%
Tier 1 capital (to average assets), for minimum capital adequacy purposes ratio	4.00%	4.00%
Total capital (to risk weighted assets), minimum to be well capitalized under prompt corrective action provisions amount	$ 29,703	$ 24,331
Tier 1 capital (to risk weighted assets), minimum to be well capitalized under prompt corrective action provisions amount	23,762	19,465
Common equity Tier 1 capital (to risk weighted assets), minimum to be well capitalized under prompt corrective action provisions amount	19,307	15,815
Tier 1 capital (to average assets), minimum to be well capitalized under prompt corrective action provisions amount	$ 24,096	$ 19,228
Total capital (to risk weighted assets), minimum to be well capitalized under prompt corrective action provisions ratio	10.00%	10.00%
Tier 1 capital (to risk weighted assets), minimum to be well capitalized under prompt corrective action provisions ratio	8.00%	8.00%
Common equity Tier 1 capital (to risk weighted assets), minimum to be well capitalized under prompt corrective action provisions ratio	6.50%	6.50%
Tier 1 capital (to average assets), minimum to be well capitalized under prompt corrective action provisions ratio	5.00%	5.00%