Impaired Loans and Valuation Allowance for Loan Losses - Modified Loans (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013 Contract
Financing Receivable, Modifications [Line Items]
Number of Contracts	18
Pre-Modification Outstanding Recorded Investment	$ 4,542
Post-Modification Outstanding Recorded Investment	4,036
Specific Reserve Recorded	0
Valuation Allowance Recorded	506
Construction and Land Development [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts	1
Pre-Modification Outstanding Recorded Investment	14
Post-Modification Outstanding Recorded Investment	14
Specific Reserve Recorded	0
Valuation Allowance Recorded	0
Residential Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts	8
Pre-Modification Outstanding Recorded Investment	990
Post-Modification Outstanding Recorded Investment	865
Specific Reserve Recorded	0
Valuation Allowance Recorded	125
Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts	7
Pre-Modification Outstanding Recorded Investment	3,421
Post-Modification Outstanding Recorded Investment	3,059
Specific Reserve Recorded	0
Valuation Allowance Recorded	362
Commercial and Financial [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts	1
Pre-Modification Outstanding Recorded Investment	25
Post-Modification Outstanding Recorded Investment	24
Specific Reserve Recorded	0
Valuation Allowance Recorded	1
Consumer [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts	1
Pre-Modification Outstanding Recorded Investment	92
Post-Modification Outstanding Recorded Investment	74
Specific Reserve Recorded	0
Valuation Allowance Recorded	$ 18