Allowance for Loan Losses - Summary of Nonaccrual Loans (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment [Line Items]
Total, Non-Accrual Status	$ 12,920	$ 13,558
Commercial and Agriculture [Member]
Financing Receivable, Recorded Investment [Line Items]
Total, Non-Accrual Status	1,496	1,264
Commercial Real Estate Owner Occupied [Member]
Financing Receivable, Recorded Investment [Line Items]
Total, Non-Accrual Status	4,054	3,403
Commercial Real Estate Non Owner Occupied [Member]
Financing Receivable, Recorded Investment [Line Items]
Total, Non-Accrual Status	1,658	2,134
Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total, Non-Accrual Status	5,608	6,674
Real Estate Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Total, Non-Accrual Status	31	41
Consumer and Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total, Non-Accrual Status	$ 73	$ 42