Allocation of Allowance for Loan Losses (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Jun. 30, 2013	Dec. 31, 2012
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses	$ 5,672	$ 5,393	$ 4,727
Allowance for loan losses, percentage of total	100.00%		100.00%
Commercial Non Real Estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses	504		420
Allowance for loan losses, percentage of total	13.70%		13.30%
Commercial Real Estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses	3,339		3,338
Allowance for loan losses, percentage of total	57.50%		63.70%
Consumer real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses	1,238		810
Allowance for loan losses, percentage of total	25.30%		19.00%
Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses	198		151
Allowance for loan losses, percentage of total	3.50%		4.00%
Unallocated
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses	$ 393		$ 8
Allowance for loan losses, percentage of total	0.00%		0.00%