Fair Values of Assets and Liabilities - Carrying Amounts and Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Fair Value Measurements Of Financial Instruments [Line Items]
Cash and due from banks	$ 100,009	$ 102,346
Interest-bearing deposits	256,572	19,510
Securities available for sale	831,223	902,292
Debt Securities, Held-to-maturity	361,844	337,123
Other investments	12,227	16,761
Premises and Equipment	442
Loans	6,761,183	6,189,148	$ 5,774,139
Deposits	7,438,666	6,677,615
Short-term borrowings	117,373	201,853	$ 721,823
Long-term debt	56,258	56,917
Subordinated Debentures outstanding, Amount	170,612	170,450
Capital lease obligation	6,385	6,815
Loans Held for Sale	33,436	15,989
Level 1 [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Securities available for sale	0	0
Other investments	0
Premises and Equipment	0
Loans Held for Sale	0	0
Fair Value, Inputs, Level 2 [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Securities available for sale	831,223	902,292
Other investments	10,557	15,091
Premises and Equipment	442
Loans Held for Sale	33,436	15,989
Level 3 [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Securities available for sale	0	0
Premises and Equipment	0
Loans Held for Sale	0	0
Carrying Amount [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Cash and due from banks	100,009	102,346
Interest-bearing deposits	256,572	19,510
Securities available for sale	831,223	902,292
Debt Securities, Held-to-maturity	361,844	337,123
Other investments	12,227	16,761
Loans held for sale	33,436	15,989
Loans	6,761,183	6,189,148
Deposits	7,438,666	6,677,615
Short-term borrowings	117,373	201,853
Long-term debt	56,258	56,917
Subordinated Debentures outstanding, Amount	170,612	170,450
Capital lease obligation	6,385	6,815
Estimated Fair Value [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Cash and due from banks	100,009	102,346
Interest-bearing deposits	256,572	19,510
Securities available for sale	831,223	902,292
Debt Securities, Held-to-maturity	369,851	338,718
Other investments	12,227	16,761
Loans held for sale	33,436	15,989
Loans	7,202,763	6,393,872
Deposits	7,440,906	6,677,595
Short-term borrowings	117,037	201,151
Long-term debt	57,881	58,051
Subordinated Debentures outstanding, Amount	165,665	171,772
Capital lease obligation	6,385	6,815
Estimated Fair Value [Member] \| Level 1 [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Cash and due from banks	100,009	102,346
Interest-bearing deposits	256,572	19,510
Securities available for sale	0	0
Debt Securities, Held-to-maturity	0	0
Other investments	0	0
Loans held for sale	0	0
Loans	0	0
Deposits	0	0
Short-term borrowings	0	0
Long-term debt	0	0
Subordinated Debentures outstanding, Amount	0	0
Capital lease obligation	0	0
Estimated Fair Value [Member] \| Fair Value, Inputs, Level 2 [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Cash and due from banks	0
Interest-bearing deposits	0	0
Securities available for sale	831,223	902,292
Debt Securities, Held-to-maturity	369,851	338,718
Other investments	10,557	15,091
Loans held for sale	33,436	15,989
Loans	35,543	12,267
Deposits	7,440,906	6,677,595
Short-term borrowings	117,037	201,151
Long-term debt	57,881	58,051
Subordinated Debentures outstanding, Amount	0	0
Capital lease obligation	6,385	6,815
Estimated Fair Value [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	0	0
Debt Securities, Held-to-maturity	0	0
Other investments	1,670	1,670
Loans held for sale	0	0
Loans	7,167,220	6,381,605
Deposits	0	0
Short-term borrowings	0	0
Long-term debt	0	0
Subordinated Debentures outstanding, Amount	165,665	171,772
Capital lease obligation	$ 0	$ 0

Fair Value Measurements Of Financial Instruments [Line Items]

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