Regulatory Matters - Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Corporation [Member]
Total Capital (to Risk-Weighted Assets):
Total Capital (to Risk-Weighted Assets) Actual, Amount	$ 249,388	$ 256,329
Total Capital (to Risk-Weighted Assets) Actual, Ratio	12.91%	13.90%
Total Capital (to Risk-Weighted Assets) For Capital Adequacy, Amount	154,589	147,568
Total Capital (to Risk-Weighted Assets) For Capital Adequacy, Ratio	8.00%	8.00%
Total Capital (to Risk-Weighted Assets) To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	193,237	184,460
Total Capital (to Risk-Weighted Assets) To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	10.00%	10.00%
Tier 1 Capital (to Risk-Weighted Assets):
Tier 1 Capital (to Risk-Weighted Assets) Actual, Amount	227,907	232,946
Tier 1 Capital (to Risk-Weighted Assets) Actual, Ratio	11.79%	12.63%
Tier 1 Capital (to Risk - Weighed Assets) For Capital Adequacy, Amount	77,295	73,784
Tier 1 Capital (to Risk - Weighted Assets) For Capital Adequacy, Ratio	4.00%	4.00%
Tier 1 Capital (to Risk-Weighted Assets) To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	115,942	110,676
Tier 1 Capital (to Risk-Weighted Assets) To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	6.00%	6.00%
Tier 1 Capital (to Average Assets):
Tier 1 Capital (to Average Assets) Actual, Amount	227,907	232,946
Tier 1 Capital (to Average Assets) Actual, Ratio	10.55%	10.85%
Tier 1 Capital (to Average Assets) For Capital Adequacy, Amount	86,371	85,876
Tier 1 Capital (to Average Assets) For Capital Adequacy, Ratio	4.00%	4.00%
Tier 1 Capital (to Average Assets) To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	107,964	107,346
Tier 1 Capital (to Average Assets) To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	5.00%	5.00%
Bank [Member]
Total Capital (to Risk-Weighted Assets):
Total Capital (to Risk-Weighted Assets) Actual, Amount	232,080	238,336
Total Capital (to Risk-Weighted Assets) Actual, Ratio	12.15%	13.06%
Total Capital (to Risk-Weighted Assets) For Capital Adequacy, Amount	152,796	145,991
Total Capital (to Risk-Weighted Assets) For Capital Adequacy, Ratio	8.00%	8.00%
Total Capital (to Risk-Weighted Assets) To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	190,995	182,489
Total Capital (to Risk-Weighted Assets) To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	10.00%	10.00%
Tier 1 Capital (to Risk-Weighted Assets):
Tier 1 Capital (to Risk-Weighted Assets) Actual, Amount	210,816	215,497
Tier 1 Capital (to Risk-Weighted Assets) Actual, Ratio	11.04%	11.81%
Tier 1 Capital (to Risk - Weighed Assets) For Capital Adequacy, Amount	76,398	72,995
Tier 1 Capital (to Risk - Weighted Assets) For Capital Adequacy, Ratio	4.00%	4.00%
Tier 1 Capital (to Risk-Weighted Assets) To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	114,597	109,493
Tier 1 Capital (to Risk-Weighted Assets) To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	6.00%	6.00%
Tier 1 Capital (to Average Assets):
Tier 1 Capital (to Average Assets) Actual, Amount	210,816	215,497
Tier 1 Capital (to Average Assets) Actual, Ratio	9.80%	10.11%
Tier 1 Capital (to Average Assets) For Capital Adequacy, Amount	86,005	85,277
Tier 1 Capital (to Average Assets) For Capital Adequacy, Ratio	4.00%	4.00%
Tier 1 Capital (to Average Assets) To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 107,506	$ 106,597
Tier 1 Capital (to Average Assets) To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	5.00%	5.00%