Loans - Summary of Composition of Loan Portfolio (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	$ 1,923,933	$ 1,731,536
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	696,173	721,506
Residential Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	241,357	255,346
Consumer Portfolio Segment Other Than Overdrafts [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	11,013	10,744
Municipal [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	135,418	85,685
Construction and Land Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	14,928	27,421
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	612,503	452,235
Home Equity [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	211,857	178,020
Overdrafts [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	$ 684	$ 579