Fair Values of Assets and Liabilities - Carrying Amounts and Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Fair Value Measurements Of Financial Instruments [Line Items]
Cash and due from banks	$ 118,413	$ 102,346
Interest-bearing deposits	15,762	19,510
Securities available for sale, at fair value	972,626	902,292
Debt Securities, Held-to-maturity	318,256	337,123
Other investments	19,415	16,761
Loans and Leases Receivable, Net of Deferred Income	6,313,944	6,189,148	$ 5,871,070
Deposits	6,923,088	6,677,615
Short-term borrowings	146,971	201,853
Subordinated debt	170,490	170,450
Long-term debt	56,755	56,917
Capital Lease Obligations	6,710	6,815
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	972,626	902,292
Other investments	17,745	15,091
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	118,413	102,346
Interest-bearing deposits	15,762	19,510
Securities available for sale, at fair value	972,626	902,292
Debt Securities, Held-to-maturity	318,256	337,123
Other investments	19,415	16,761
Loans Held for sale, Amount	25,783	15,989
Loans and Leases Receivable, Net of Deferred Income	6,313,944	6,189,148
Deposits	6,923,088	6,677,615
Short-term borrowings	146,971	201,853
Subordinated debt	170,490	170,450
Long-term debt	56,755	56,917
Capital Lease Obligations	6,710	6,815
Estimate of Fair Value Measurement [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Cash and due from banks	118,413	102,346
Interest-bearing deposits	15,762	19,510
Securities available for sale, at fair value	972,626	902,292
Debt Securities, Held-to-maturity	327,592	338,718
Other investments	19,415	16,761
Loans Held for sale, Amount	25,783	15,989
Loans and Leases Receivable, Net of Deferred Income	6,702,184	6,393,872
Deposits	6,930,139	6,677,595
Short-term borrowings	146,405	201,151
Subordinated debt	156,508	171,772
Long-term debt	58,804	58,051
Capital Lease Obligations	6,710	6,815
Estimate of Fair Value Measurement [Member] | Level 1 [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Cash and due from banks	118,413	102,346
Interest-bearing deposits	15,762	19,510
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	972,626	902,292
Debt Securities, Held-to-maturity	327,592	338,718
Other investments	17,745	15,091
Loans Held for sale, Amount	25,783	15,989
Loans and Leases Receivable, Net of Deferred Income	34,995	12,267
Deposits	6,930,139	6,677,595
Short-term borrowings	146,405	201,151
Subordinated debt	0	0
Long-term debt	58,804	58,051
Capital Lease Obligations	6,710	6,815
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	6,667,189	6,381,605
Deposits	0	0
Short-term borrowings	0	0
Subordinated debt	156,508	171,772
Long-term debt	0	0
Capital Lease Obligations	$ 0	$ 0