Loans - Schedule of Loans Not Rated by Class of Loans (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Financing Receivable, Recorded Investment [Line Items]
Loans not rated by class of loans	$ 122,879	$ 120,685
Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans not rated by class of loans	424	285
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans not rated by class of loans	1,823	2,460
Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans not rated by class of loans	112,528	110,159
Construction & Land Development [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans not rated by class of loans	1,266	1,301
Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans not rated by class of loans	6,838	6,480
Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans not rated by class of loans	121,813	119,795
Performing [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans not rated by class of loans	424	285
Performing [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans not rated by class of loans	1,823	2,460
Performing [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans not rated by class of loans	111,462	109,276
Performing [Member] | Construction & Land Development [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans not rated by class of loans	1,266	1,294
Performing [Member] | Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans not rated by class of loans	6,838	6,480
Non-Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans not rated by class of loans	1,066	890
Non-Performing [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans not rated by class of loans
Non-Performing [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans not rated by class of loans
Non-Performing [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans not rated by class of loans	1,066	883
Non-Performing [Member] | Construction & Land Development [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans not rated by class of loans		7
Non-Performing [Member] | Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans not rated by class of loans