Regulatory Capital Requirements - Additional Information (Detail)	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Jan. 31, 2013	Jun. 30, 2012
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 capital to average total assets, ratio	10.26%	8.70%	8.50%	9.00%
Minimum total risk-based Capital Ratio	12.00%
Maximum period to restore capital ratio to required level	90 days
Minimum Tier 1 leverage ratio to prevent from restoring capital ratios		9.00%
Bank's commitment, effective date	Mar. 31, 2013
Total risk-based capital to risk-weighted assets, ratio	19.78%		12.00%	12.00%
Minimum [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 capital to risk-weighted assets, ratio	4.50%
Tier 1 capital to risk-based assets	4.00%
Higher risk weight	150.00%
Period of nonaccrual status	90 days
Common equity Tier 1 capital risk-based weighted assets	2.50%
Maximum [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 capital to risk-based assets	6.00%
Minimum Capital Requirements Per Memorandum of Understanding [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 capital to average total assets, ratio	8.50%
Total risk-based capital to risk-weighted assets, ratio	12.00%
Tier 1 capital to risk-weighted assets, ratio