Loans - Schedule of Net Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Loan Portfolio By Loan Grade [Line Items]
Loans	$ 2,809,197	$ 2,479,348
Less: unearned discount	(5,162)	(4,791)
allowance for loan losses	(19,473)	(19,704)
Net loans	2,784,562	2,454,853
Commercial, industrial, and agricultural
Loan Portfolio By Loan Grade [Line Items]
Loans	1,046,665	916,297
Net loans	1,046,665	916,297
Commercial mortgages
Loan Portfolio By Loan Grade [Line Items]
Loans	814,002	697,776
Net loans	814,002	697,776
Residential real estate
Loan Portfolio By Loan Grade [Line Items]
Loans	814,030	771,309
Consumer
Loan Portfolio By Loan Grade [Line Items]
Loans	124,785	86,035
Credit cards
Loan Portfolio By Loan Grade [Line Items]
Loans	7,569	7,623
Overdrafts
Loan Portfolio By Loan Grade [Line Items]
Loans	$ 2,146	$ 308

Loan portfolio by loan grade.

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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Amount of deferred interest and fee income, unamortized costs incurred to originate loans and leases, unamortized loan commitments and loan syndication fees, and premiums over or discounts from face amounts of acquired loans. Excludes amounts for loans and leases covered under loss sharing agreements.

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Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements and loans held for sale.

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