Fair Values of Assets and Liabilities - Carrying Amounts and Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair Value Measurements Of Financial Instruments [Line Items]
Cash and due from banks	$ 95,934	$ 98,624
Interest-bearing deposits	3,013	8,668
Securities available for sale	909,247	731,358
Debt Securities, Held-to-maturity	393,855	422,096
Other investments	32,126	29,837
Loans	5,774,139	5,407,376	$ 4,879,347
Deposits	5,897,992	5,580,705
Short-term borrowings	721,823	707,466	$ 867,943
Long-term debt	7,551	8,161
Subordinated Debentures outstanding, Amount	170,288	72,167
Capital Lease Obligations, Current	7,217	7,590
Level 1 [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Securities available for sale	0	0
Other investments	0
Fair Value, Inputs, Level 2 [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Securities available for sale	909,247	706,042
Other investments	30,456
Level 3 [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Securities available for sale	0	25,316
Carrying Amount [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Cash and due from banks	95,934	98,624
Interest-bearing deposits	3,013	8,668
Securities available for sale	909,247	731,358
Debt Securities, Held-to-maturity	393,855	422,096
Other investments	32,126	29,837
Loans held for sale	11,881	14,850
Loans	5,774,139	5,407,376
Deposits	5,897,992	5,580,705
Short-term borrowings	721,823	707,466
Long-term debt	7,551	8,161
Subordinated Debentures outstanding, Amount	170,288	72,167
Capital Lease Obligations, Current	7,217	7,590
Estimated Fair Value [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Cash and due from banks	95,934	98,624
Interest-bearing deposits	3,013	8,668
Securities available for sale	909,247	731,358
Debt Securities, Held-to-maturity	383,993	418,249
Other investments	32,126	29,837
Loans held for sale	11,881	14,850
Loans	5,821,791	5,443,434
Deposits	5,904,147	5,580,812
Short-term borrowings	721,532	707,263
Long-term debt	7,720	8,548
Subordinated Debentures outstanding, Amount	168,067	65,785
Capital Lease Obligations, Current	7,217	7,590
Estimated Fair Value [Member] \| Level 1 [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Cash and due from banks	95,934	98,624
Interest-bearing deposits	3,013	8,668
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 Obligations, Current	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	0
Interest-bearing deposits	0	0
Securities available for sale	909,247	706,042
Debt Securities, Held-to-maturity	383,993	418,249
Other investments	30,456	29,837
Loans held for sale	11,881	14,850
Loans	15,076	23,249
Deposits	5,904,147	5,580,812
Short-term borrowings	721,532	707,263
Long-term debt	7,720	8,548
Subordinated Debentures outstanding, Amount	0	0
Capital Lease Obligations, Current	7,217	7,590
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	25,316
Debt Securities, Held-to-maturity	0	0
Other investments	1,670	0
Loans held for sale	0	0
Loans	5,806,715	5,420,185
Deposits	0	0
Short-term borrowings	0	0
Long-term debt	0	0
Subordinated Debentures outstanding, Amount	168,067	65,785
Capital Lease Obligations, Current	$ 0	$ 0

Fair Value Measurements Of Financial Instruments [Line Items]

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