Allowance for Loan Losses - Schedule of Troubled Debt Restructurings (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013 Contract	Sep. 30, 2012 Contract	Sep. 30, 2013 Contract	Sep. 30, 2012 Contract
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number of Contracts	1	4	2	35
Pre-Modification Outstanding Recorded Investment	$ 422	$ 601	$ 547	$ 3,505
Post-Modification Outstanding Recorded Investment	422	901	547	3,419
Commercial and Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number of Contracts		2		6
Pre-Modification Outstanding Recorded Investment		197		983
Post-Modification Outstanding Recorded Investment		497		976
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number of Contracts	1		2	3
Pre-Modification Outstanding Recorded Investment	422		547	1,206
Post-Modification Outstanding Recorded Investment	422		547	1,206
Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number of Contracts		1		21
Pre-Modification Outstanding Recorded Investment		385		1,250
Post-Modification Outstanding Recorded Investment		385		1,171
Real Estate Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number of Contracts
Pre-Modification Outstanding Recorded Investment
Post-Modification Outstanding Recorded Investment
Consumer and Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number of Contracts		1		5
Pre-Modification Outstanding Recorded Investment		19		66
Post-Modification Outstanding Recorded Investment		$ 19		$ 66