Loans and Allowance for Loan Losses - Schedule of Change in Troubled Debt Restructuring (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Financing Receivable Modifications Number Of Contracts [Line Items]
Post-Modification Principal Balance	$ 7,834	$ 12,516
Change	(4,682)
Construction, Land Development and Other Land Loans [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Post-Modification Principal Balance	5,279	9,988
Change	(4,709)
Secured by 1-4 Family Residential Properties [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Post-Modification Principal Balance	591	586
Change	5
Secured by Non-farm, Non-residential Properties [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Post-Modification Principal Balance	1,633	1,586
Change	47
Commercial loans [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Post-Modification Principal Balance	331	356
Change	$ (25)