Regulatory Capital - Summary of Regulatory Capital Requirement (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Schedule Of Regulatory Assets And Liabilities [Line Items]
Total capital (to risk-weighted assets), Actual, Amount	$ 251,434	$ 264,452
Total capital (to risk-weighted assets), Actual, Ratio	13.57%	13.99%
Total capital (to risk-weighted assets), For capital adequacy purposes, Amount	$ 159,902	$ 151,223
Total capital (to risk-weighted assets), For capital adequacy purposes, Ratio	8.63%	8.00%
Tier 1 capital (to average assets), Actual, Amount	$ 203,797	$ 249,918
Tier 1 capital (to average assets), Actual, Ratio	12.80%	13.22%
Tier 1 capital (to average assets), For capital adequacy purposes, Amount	$ 105,560	$ 113,427
Tier 1 capital (to average assets), For capital adequacy purpose, Ratio	6.63%	6.00%
Common equity tier 1 capital, Actual Amount	$ 203,797	$ 204,350
Common equity tier 1 capital, Actual Ratio	11.00%	10.81%
Common equity tier 1 capital,For capital adequacy purposes, Amount	$ 95,044	$ 85,067
Common equity tier 1 capital, For capital adequacy purpose, Ratio	5.13%	4.50%
Tier 1 capital (to average assets), Actual, Amount	$ 237,198	$ 249,918
Tier 1 capital (to average assets), Actual, Ratio	9.32%	9.82%
Tier 1 capital (to average assets), For capital adequacy purposes, Amount	$ 101,802	$ 101,800
Tier 1 capital (to average assets), For capital adequacy purpose, Ratio	4.00%	4.00%
Bank [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Total capital (to risk-weighted assets), Actual, Amount	$ 242,478	$ 237,348
Total capital (to risk-weighted assets), Actual, Ratio	13.10%	12.57%
Total capital (to risk-weighted assets), For capital adequacy purposes, Amount	$ 159,739	$ 151,057
Total capital (to risk-weighted assets), For capital adequacy purposes, Ratio	8.63%	8.00%
Total capital (to risk-weighted assets), For well capitalized purpose, Amount	$ 185,098	$ 188,821
Total capital (to risk-weighted assets), For well capitalized purpose, Ratio	10.00%	10.00%
Tier 1 capital (to average assets), Actual, Amount	$ 228,242	$ 222,814
Tier 1 capital (to average assets), Actual, Ratio	12.33%	11.80%
Tier 1 capital (to average assets), For capital adequacy purposes, Amount	$ 122,729	$ 113,295
Tier 1 capital (to average assets), For capital adequacy purpose, Ratio	6.63%	6.00%
Tier 1 capital (to average assets), For well capitalized purpose, Amount	$ 148,089	$ 151,060
Tier 1 capital (to average assets), For well capitalized purposes, Ratio	8.00%	8.00%
Common equity tier 1 capital, Actual Amount	$ 228,242	$ 222,814
Common equity tier 1 capital, Actual Ratio	12.33%	11.80%
Common equity tier 1 capital,For capital adequacy purposes, Amount	$ 94,962	$ 84,971
Common equity tier 1 capital, For capital adequacy purpose, Ratio	5.13%	4.50%
Common equity tier 1 capital, For well capitalized purpose, Amount	$ 120,322	$ 122,737
Common equity tier 1 capital, For well capitalized purposes, Ratio	6.50%	6.50%
Tier 1 capital (to average assets), Actual, Amount	$ 228,242	$ 222,814
Tier 1 capital (to average assets), Actual, Ratio	8.98%	8.77%
Tier 1 capital (to average assets), For capital adequacy purposes, Amount	$ 101,667	$ 101,626
Tier 1 capital (to average assets), For capital adequacy purpose, Ratio	4.00%	4.00%
Tier 1 capital (to average assets), For well capitalized purpose, Amount	$ 127,084	$ 127,032
Tier 1 capital (to average assets), For well capitalized purposes, Ratio	5.00%	5.00%