Loans (Impaired Loans) - Additional Information (Detail) - USD ($)	6 Months Ended
	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired loans classified as troubled debt restructured	$ 1,300,000	$ 797,200	$ 964,000
Troubled debt restructuring	$ 0		$ 0
Maximum time for re-evaluation (in months)	12 months
Re-evaluation period for real estate	2 years
Unsecured consumer loans, credit card credits and overdraft lines of credit reach	90 days
Delinquent period for charging down consumer loans	120 days
Delinquent period for charging down commercial and agricultural credits	120 days
Foreclosed residential real estate property	$ 1,098,000	$ 1,094,000
Consumer Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Foreclosed residential real estate property	452,000
Residential real estate properties foreclosure proceedings	$ 138,000