Loans - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Specific reserves to customers whose loan terms have been modified in troubled debt restructurings	$ 0	$ 1,945
Charge-offs due to troubled debt restructurings	0	834
Defaulted payment following modification for troubled debt restructurings	1,942	527
Loans individually analyzed for credit quality based on credit risk, individual outstanding balance	2	10
Provision for Loan Losses	2,230	4,226
Troubled Debt Restructuring [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for Loan Losses	88	77
Subsequently Defaulted [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Specific reserves to customers whose loan terms have been modified in troubled debt restructurings	12	500
Charge-offs due to troubled debt restructurings	$ 306	$ 500