Unpaid Principal Balance and Recorded Investment of Loans Modified and Classified as TDRs (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Financing Receivable, Modifications [Line Items]
Unpaid Principal Balance of TDRs	$ 776
Recorded Investment of TDRs With Allowance
Recorded Investment of TDRs Without Allowance	246
Total Recorded Investment of TDR	246
Residential real estate loans
Financing Receivable, Modifications [Line Items]
Unpaid Principal Balance of TDRs	726
Recorded Investment of TDRs With Allowance
Recorded Investment of TDRs Without Allowance	208
Total Recorded Investment of TDR	208
Commercial real estate loans
Financing Receivable, Modifications [Line Items]
Unpaid Principal Balance of TDRs	50
Recorded Investment of TDRs With Allowance
Recorded Investment of TDRs Without Allowance	38
Total Recorded Investment of TDR	38
Commercial loans
Financing Receivable, Modifications [Line Items]
Recorded Investment of TDRs With Allowance