Capital Requirements and Restrictions on Retained Earnings - Summary of Actual and Required Capital Amounts and Ratios (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Consolidated
Total Capital to Risk Weighted Assets
Total Capital to Risk Weighted Assets, Actual Amount	$ 319,340	$ 297,708
Total Capital to Risk Weighted Assets, Actual Ratio	13.21%	14.32%
Total Capital to Risk Weighted Assets, For Capital Adequacy Purposes Amount	$ 238,719	$ 192,341
Total Capital to Risk Weighted Assets, For Capital Adequacy Purposes Ratio	9.875%	9.25%
Tier 1 (Core) Capital to Risk Weighted Assets
Tier 1 (Core) Capital to Risk Weighted Assets, Actual Amount	$ 249,636	$ 228,015
Tier 1 (Core) Capital to Risk Weighted Assets, Actual Ratio	10.33%	10.97%
Tier 1 (Core) Capital to Risk Weighted Assets, For Capital Adequacy Purposes Amount	$ 190,371	$ 150,754
Tier 1 (Core) Capital to Risk Weighted Assets, For Capital Adequacy Purposes Ratio	7.875%	7.25%
Common equity Tier 1 to Risk Weighted Assets
Common equity Tier 1 to Risk Weighted Assets, Actual Amount	$ 229,636	$ 208,015
Common equity Tier 1 to Risk Weighted Assets, Actual Ratio	9.50%	10.00%
Common equity Tier 1 to Risk Weighted Assets, For Capital Adequacy Purposes Amount	$ 154,110	$ 119,563
Common equity Tier 1 to Risk Weighted Assets, For Capital Adequacy Purposes Ratio	6.375%	5.75%
Tier 1 (Core) Capital to Average Assets
Tier 1 (Core) Capital to Average Assets, Actual Amount	$ 249,636	$ 228,015
Tier 1 (Core) Capital to Average Assets, Actual Ratio	7.87%	8.45%
Tier 1 (Core) Capital to Average Assets, For Capital Adequacy Purposes, Amount	$ 126,882	$ 107,969
Tier 1 (Core) Capital to Average Assets, For Capital Adequacy Purposes, Ratio	4.00%	4.00%
Bank
Total Capital to Risk Weighted Assets
Total Capital to Risk Weighted Assets, Actual Amount	$ 302,627	$ 279,704
Total Capital to Risk Weighted Assets, Actual Ratio	12.59%	13.58%
Total Capital to Risk Weighted Assets, For Capital Adequacy Purposes Amount	$ 237,325	$ 190,513
Total Capital to Risk Weighted Assets, For Capital Adequacy Purposes Ratio	9.875%	9.25%
Total Capital to Risk Weighted Assets, To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 240,329	$ 205,960
Total Capital to Risk Weighted Assets, To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio	10.00%	10.00%
Tier 1 (Core) Capital to Risk Weighted Assets
Tier 1 (Core) Capital to Risk Weighted Assets, Actual Amount	$ 284,722	$ 261,643
Tier 1 (Core) Capital to Risk Weighted Assets, Actual Ratio	11.85%	12.70%
Tier 1 (Core) Capital to Risk Weighted Assets, For Capital Adequacy Purposes Amount	$ 189,259	$ 149,321
Tier 1 (Core) Capital to Risk Weighted Assets, For Capital Adequacy Purposes Ratio	7.875%	7.25%
Tier 1 (Core) Capital to Risk Weighted Assets, To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 192,263	$ 164,768
Tier 1 (Core) Capital to Risk Weighted Assets, To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	8.00%	8.00%
Common equity Tier 1 to Risk Weighted Assets
Common equity Tier 1 to Risk Weighted Assets, Actual Amount	$ 277,343	$ 254,264
Common equity Tier 1 to Risk Weighted Assets, Actual Ratio	11.54%	12.35%
Common equity Tier 1 to Risk Weighted Assets, For Capital Adequacy Purposes Amount	$ 153,210	$ 118,427
Common equity Tier 1 to Risk Weighted Assets, For Capital Adequacy Purposes Ratio	6.375%	5.75%
Common equity Tier 1 to Risk Weighted Assets, To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 156,214	$ 133,874
Common equity Tier 1 to Risk Weighted Assets, To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	6.50%	6.50%
Tier 1 (Core) Capital to Average Assets
Tier 1 (Core) Capital to Average Assets, Actual Amount	$ 284,722	$ 261,643
Tier 1 (Core) Capital to Average Assets, Actual Ratio	9.12%	9.80%
Tier 1 (Core) Capital to Average Assets, For Capital Adequacy Purposes, Amount	$ 124,903	$ 106,798
Tier 1 (Core) Capital to Average Assets, For Capital Adequacy Purposes, Ratio	4.00%	4.00%
Tier 1 (Core) Capital to Average Assets, To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 156,128	$ 133,498
Tier 1 (Core) Capital to Average Assets, To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	5.00%	5.00%