Loans - Nonaccrual Loans and Loans Past Due over 90 Days Still Accruing Interest by Class of Loans (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	$ 10,412	$ 11,573
Past Due Over 90 Days Still on Accrual	350	344
Commercial, Industrial, and Agricultural [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	1,272	1,006
Past Due Over 90 Days Still on Accrual	0	0
Commercial Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	5,002	7,236
Past Due Over 90 Days Still on Accrual	199	0
Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	3,048	2,389
Past Due Over 90 Days Still on Accrual	106	150
Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	1,090	942
Past Due Over 90 Days Still on Accrual	0	170
Credit Cards [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	0	0
Past Due Over 90 Days Still on Accrual	$ 45	$ 24