Allowance for Loan Losses - Summary of Nonaccrual Loans (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Financing Receivable, Recorded Investment [Line Items]
Total, Non-Accrual Status	$ 21,184	$ 20,459
Commercial and Agriculture [Member]
Financing Receivable, Recorded Investment [Line Items]
Total, Non-Accrual Status	2,438	1,590
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total, Non-Accrual Status	9,521	9,609
Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total, Non-Accrual Status	9,171	9,210
Real Estate Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Total, Non-Accrual Status
Consumer and other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total, Non-Accrual Status	$ 54	$ 50