Fair Values of Assets and Liabilities - Carrying Amounts and Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020
Fair Value Measurements Of Financial Instruments [Line Items]
Cash and due from banks	$ 83,989	$ 100,009
Interest-bearing deposits	420,645	256,572
Securities available for sale, at fair value	1,043,258	831,223
Debt Securities, Held-to-maturity	407,833	361,844
Other investments	13,445	12,227
Loans and Leases Receivable, Net of Deferred Income	6,736,894	6,761,183	$ 6,313,944
Deposits	7,869,256	7,438,666
Short-term borrowings	110,762	117,373
Subordinated debt	170,653	170,612
Long-term debt	56,089	56,258
Capital Lease Obligations	6,270	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	1,043,258	831,223
Other investments	11,775	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	83,989	100,009
Interest-bearing deposits	420,645	256,572
Securities available for sale, at fair value	1,043,258	831,223
Debt Securities, Held-to-maturity	407,833	361,844
Other investments	13,445	12,227
Loans Held for sale, Amount	20,604	33,436
Loans and Leases Receivable, Net of Deferred Income	6,736,894	6,761,183
Deposits	7,869,256	7,438,666
Short-term borrowings	110,762	117,373
Subordinated debt	170,653	170,612
Long-term debt	56,089	56,258
Capital Lease Obligations	6,270	6,385
Estimate of Fair Value Measurement [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Cash and due from banks	83,989	100,009
Interest-bearing deposits	420,645	256,572
Securities available for sale, at fair value	1,043,258	831,223
Debt Securities, Held-to-maturity	408,118	369,851
Other investments	13,445	12,227
Loans Held for sale, Amount	20,604	33,436
Loans and Leases Receivable, Net of Deferred Income	7,111,000	7,202,763
Deposits	7,869,730	7,440,906
Short-term borrowings	110,446	117,037
Subordinated debt	172,619	165,665
Long-term debt	57,276	57,881
Capital Lease Obligations	6,270	6,385
Estimate of Fair Value Measurement [Member] | Level 1 [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Cash and due from banks	83,989	100,009
Interest-bearing deposits	420,645	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	1,043,258	831,223
Debt Securities, Held-to-maturity	408,118	369,851
Other investments	11,775	10,557
Loans Held for sale, Amount	20,604	33,436
Loans and Leases Receivable, Net of Deferred Income	29,467	35,543
Deposits	7,869,730	7,440,906
Short-term borrowings	110,446	117,037
Subordinated debt	0	0
Long-term debt	57,276	57,881
Capital Lease Obligations	6,270	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	7,081,533	7,167,220
Deposits	0	0
Short-term borrowings	0	0
Subordinated debt	172,619	165,665
Long-term debt	0	0
Capital Lease Obligations	$ 0	$ 0