Fair Value Disclosures of Financial Assets (Estimated Fair Value of Off-Balance Sheet Financial Instruments) (Detail) (Commitments To Extend Credit [Member], USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Commitments To Extend Credit [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commitments to extend credit	$ 5,123	$ 4,445