Fair Values of Assets and Liabilities - Carrying Amounts and Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Fair Value Measurements Of Financial Instruments [Line Items]
Cash and due from banks	$ 108,970	$ 102,346
Interest-bearing deposits	348,763	19,510
Securities available for sale, at fair value	902,140	902,292
Debt Securities, Held-to-maturity	297,986	337,123
Other investments	12,272	16,761
Loans and Leases Receivable, Net of Deferred Income	6,922,075	6,189,148	$ 6,003,059
Deposits	7,782,201	6,677,615
Short-term borrowings	108,484	201,853
Subordinated debt	170,531	170,450
Long-term debt	56,590	56,917
Capital Lease Obligations	6,602	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	902,140	902,292
Other investments	10,602	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	108,970	102,346
Interest-bearing deposits	348,763	19,510
Securities available for sale, at fair value	902,140	902,292
Debt Securities, Held-to-maturity	297,986	337,123
Other investments	12,272	16,761
Loans Held for sale, Amount	30,409	15,989
Loans and Leases Receivable, Net of Deferred Income	6,922,075	6,189,148
Deposits	7,782,201	6,677,615
Short-term borrowings	108,484	201,853
Subordinated debt	170,531	170,450
Long-term debt	56,590	56,917
Capital Lease Obligations	6,602	6,815
Estimate of Fair Value Measurement [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Cash and due from banks	108,970	102,346
Interest-bearing deposits	348,763	19,510
Securities available for sale, at fair value	902,140	902,292
Debt Securities, Held-to-maturity	307,874	338,718
Other investments	12,272	16,761
Loans Held for sale, Amount	30,409	15,989
Loans and Leases Receivable, Net of Deferred Income	7,273,280	6,393,872
Deposits	7,788,041	6,677,595
Short-term borrowings	107,903	201,151
Subordinated debt	159,149	171,772
Long-term debt	58,476	58,051
Capital Lease Obligations	6,602	6,815
Estimate of Fair Value Measurement [Member] | Level 1 [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Cash and due from banks	108,970	102,346
Interest-bearing deposits	348,763	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	902,140	902,292
Debt Securities, Held-to-maturity	307,874	338,718
Other investments	10,602	15,091
Loans Held for sale, Amount	30,409	15,989
Loans and Leases Receivable, Net of Deferred Income	30,026	12,267
Deposits	7,788,041	6,677,595
Short-term borrowings	107,903	201,151
Subordinated debt	0	0
Long-term debt	58,476	58,051
Capital Lease Obligations	6,602	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	7,243,254	6,381,605
Deposits	0	0
Short-term borrowings	0	0
Subordinated debt	159,149	171,772
Long-term debt	0	0
Capital Lease Obligations	$ 0	$ 0