Loans - Summary of Composition of Loan Portfolio (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	$ 2,426,119	$ 2,285,578
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	786,102	750,362
Residential Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	371,897	348,250
Consumer Portfolio Segment Other Than Overdrafts [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	21,071	21,359
Municipal [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	120,455	97,290
Construction and land development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	8,992	13,628
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	812,417	761,625
Home Equity [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	304,363	292,340
Overdrafts [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	$ 822	$ 724