Fair Values of Assets and Liabilities - Carrying Amounts and Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018
Fair Value Measurements Of Financial Instruments [Line Items]
Cash and due from banks	$ 112,241	$ 95,934
Interest-bearing deposits	16,408	3,013
Securities available for sale, at fair value	812,383	909,247
Debt Securities, Held-to-maturity	357,890	393,855
Other investments	11,561	32,126
Loans and Leases Receivable, Net of Deferred Income	6,099,561	5,774,139	$ 5,662,782
Deposits	6,677,996	5,897,992
Short-term borrowings	83,735	721,823
Subordinated debt	170,409	170,288
Long-term debt	57,078	7,551
Capital Lease Obligations	6,917	7,217
Level 1 [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Securities available for sale, at fair value	0	0
Other investments	0	0
Level 2 [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Securities available for sale, at fair value	812,383	909,247
Other investments	9,891	30,456
Level 3 [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Securities available for sale, at fair value	0	0
Other investments	1,670	1,670
Carrying Amount [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Cash and due from banks	112,241	95,934
Interest-bearing deposits	16,408	3,013
Securities available for sale, at fair value	812,383	909,247
Debt Securities, Held-to-maturity	357,890	393,855
Other investments	11,561	32,126
Loans Held for sale, Amount	20,288	11,881
Loans and Leases Receivable, Net of Deferred Income	6,099,561	5,774,139
Deposits	6,677,996	5,897,992
Short-term borrowings	83,735	721,823
Subordinated debt	170,409	170,288
Long-term debt	57,078	7,551
Capital Lease Obligations	6,917	7,217
Estimate of Fair Value Measurement [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Cash and due from banks	112,241	95,934
Interest-bearing deposits	16,408	3,013
Securities available for sale, at fair value	812,383	909,247
Debt Securities, Held-to-maturity	360,224	383,993
Other investments	11,561	32,126
Loans Held for sale, Amount	20,288	11,881
Loans and Leases Receivable, Net of Deferred Income	6,213,529	5,821,791
Deposits	6,685,082	5,904,147
Short-term borrowings	83,698	721,532
Subordinated debt	169,601	168,067
Long-term debt	57,389	7,720
Capital Lease Obligations	6,917	7,217
Estimate of Fair Value Measurement [Member] \| Level 1 [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Cash and due from banks	112,241	95,934
Interest-bearing deposits	16,408	3,013
Securities available for sale, at fair value	0	0
Debt Securities, Held-to-maturity	0	0
Other investments	0	0
Loans Held for sale, Amount	0	0
Loans and Leases Receivable, Net of Deferred Income	0	0
Deposits	0	0
Short-term borrowings	0	0
Subordinated debt	0	0
Long-term debt	0	0
Capital Lease Obligations	0	0
Estimate of Fair Value Measurement [Member] \| Level 2 [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Cash and due from banks	0	0
Interest-bearing deposits	0	0
Securities available for sale, at fair value	812,383	909,247
Debt Securities, Held-to-maturity	360,224	383,993
Other investments	9,891	30,456
Loans Held for sale, Amount	20,288	11,881
Loans and Leases Receivable, Net of Deferred Income	20,407	15,076
Deposits	6,685,082	5,904,147
Short-term borrowings	83,698	721,532
Subordinated debt	0	0
Long-term debt	57,389	7,720
Capital Lease Obligations	6,917	7,217
Estimate of Fair Value Measurement [Member] \| Level 3 [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Cash and due from banks	0	0
Interest-bearing deposits	0	0
Securities available for sale, at fair value	0	0
Debt Securities, Held-to-maturity	0	0
Other investments	1,670	1,670
Loans Held for sale, Amount	0	0
Loans and Leases Receivable, Net of Deferred Income	6,193,122	5,806,715
Deposits	0	0
Short-term borrowings	0	0
Subordinated debt	169,601	168,067
Long-term debt	0	0
Capital Lease Obligations	$ 0	$ 0

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Amount equal to the present value (the principal) at the beginning of the lease term of minimum lease payments during the lease term (excluding that portion of the payments representing executory costs such as insurance, maintenance, and taxes to be paid by the lessor, together with any profit thereon) net of payments or other amounts applied to the principal through the balance sheet date.

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For banks and other depository institutions: Includes cash on hand (currency and coin), cash items in process of collection, noninterest bearing deposits due from other financial institutions (including corporate credit unions), and noninterest bearing balances with the Federal Reserve Banks, Federal Home Loan Banks and central banks.

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The aggregate of all deposit liabilities held by the entity, including foreign and domestic, interest and noninterest bearing; may include demand deposits, saving deposits, Negotiable Order of Withdrawal (NOW) and time deposits among others.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount of investment in debt security measured at amortized cost (held-to-maturity).

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For banks and other depository institutions (including Federal Reserve Banks, if applicable): Interest-bearing deposits in other financial institutions for relatively short periods of time including, for example, certificates of deposits, which are presented separately from cash on the balance sheet.

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Amount before allowance and after 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.

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Amount of investments classified as other.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of subordinated debt (with initial maturities beyond one year or beyond the operating cycle if longer). Subordinated debt places a lender in a lien position behind debt having a higher priority of repayment in liquidation of the entity's assets.

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