Expenses Applicable to Other Real Estate Owned (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended		12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Real Estate Properties [Line Items]
Loss on sales of OREO
Valuation adjustments	166	204	627
Operating expenses, net of rental income	82	65
Total OREO expense	$ 248	$ 269