Fair Values of Assets and Liabilities - Carrying Amounts and Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020
Fair Value Measurements Of Financial Instruments [Line Items]
Cash and due from banks	$ 89,505	$ 100,009
Interest-bearing deposits	194,948	256,572
Securities available for sale, at fair value	1,090,530	831,223
Debt Securities, Held-to-maturity	554,225	361,844
Other investments	11,527	12,227
Loans and Leases Receivable, Net of Deferred Income	6,740,535	6,761,183	$ 6,922,075
Deposits	7,885,019	7,438,666
Short-term borrowings	107,372	117,373
Subordinated debt	170,694	170,612
Long-term debt	5,918	56,258
Capital Lease Obligations	6,155	6,385
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	1,090,530	831,223
Other investments	9,857	10,557
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	89,505	100,009
Interest-bearing deposits	194,948	256,572
Securities available for sale, at fair value	1,090,530	831,223
Debt Securities, Held-to-maturity	554,225	361,844
Other investments	11,527	12,227
Loans Held for sale, Amount	19,530	33,436
Loans and Leases Receivable, Net of Deferred Income	6,740,535	6,761,183
Deposits	7,885,019	7,438,666
Short-term borrowings	107,372	117,373
Subordinated debt	170,694	170,612
Long-term debt	5,918	56,258
Capital Lease Obligations	6,155	6,385
Estimate of Fair Value Measurement [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Cash and due from banks	89,505	100,009
Interest-bearing deposits	194,948	256,572
Securities available for sale, at fair value	1,090,530	831,223
Debt Securities, Held-to-maturity	555,820	369,851
Other investments	11,527	12,227
Loans Held for sale, Amount	19,530	33,436
Loans and Leases Receivable, Net of Deferred Income	7,117,132	7,202,763
Deposits	7,885,040	7,440,906
Short-term borrowings	106,922	117,037
Subordinated debt	174,902	165,665
Long-term debt	6,617	57,881
Capital Lease Obligations	6,155	6,385
Estimate of Fair Value Measurement [Member] | Level 1 [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Cash and due from banks	89,505	100,009
Interest-bearing deposits	194,948	256,572
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	1,090,530	831,223
Debt Securities, Held-to-maturity	555,820	369,851
Other investments	9,857	10,557
Loans Held for sale, Amount	19,530	33,436
Loans and Leases Receivable, Net of Deferred Income	32,510	35,543
Deposits	7,885,040	7,440,906
Short-term borrowings	106,922	117,037
Subordinated debt	0	0
Long-term debt	6,617	57,881
Capital Lease Obligations	6,155	6,385
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	7,084,622	7,167,220
Deposits	0	0
Short-term borrowings	0	0
Subordinated debt	174,902	165,665
Long-term debt	0	0
Capital Lease Obligations	$ 0	$ 0