Loans - Summary of Loan Balances (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	$ 819,571	$ 815,553
Allowance for loan losses	(17,297)	(19,742)
Net loans	802,274	795,811
Commercial and Agriculture [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	105,830	100,661
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	431,733	434,808
Residential Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	244,393	250,598
Real Estate Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	26,661	19,677
Consumer and Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	$ 10,954	$ 9,809