Loans - Allowance for Loan Losses and Recorded Investment in Loans by Portfolio Segment and Based on Impairment Method (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Allowance For Loan Losses And Recorded Investment In Loans [Line Items]
Individually evaluated for impairment	$ 20,771	$ 17
Collectively evaluated for impairment	24,665	23,434
Total ending allowance balance	45,436	23,451
Individually evaluated for impairment	27,035	5,654
Collectively evaluated for impairment	2,789,429	2,669,289
Total	2,816,464	2,674,943
Construction and Land Development
Allowance For Loan Losses And Recorded Investment In Loans [Line Items]
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	4,847	4,743
Total ending allowance balance	4,847	4,743
Individually evaluated for impairment	30	2,298
Collectively evaluated for impairment	591,511	582,142
Total	591,541	584,440
Commercial Real Estate
Allowance For Loan Losses And Recorded Investment In Loans [Line Items]
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	8,113	6,725
Total ending allowance balance	8,113	6,725
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	993,912	805,260
Total	993,912	805,260
Residential Real Estate
Allowance For Loan Losses And Recorded Investment In Loans [Line Items]
Individually evaluated for impairment	17	0
Collectively evaluated for impairment	4,445	4,743
Total ending allowance balance	4,462	4,743
Individually evaluated for impairment	2,477	3,189
Collectively evaluated for impairment	641,124	679,693
Total	643,601	682,882
Commercial and Industrial
Allowance For Loan Losses And Recorded Investment In Loans [Line Items]
Individually evaluated for impairment	20,754	17
Collectively evaluated for impairment	7,203	7,149
Total ending allowance balance	27,957	7,166
Individually evaluated for impairment	24,528	167
Collectively evaluated for impairment	558,113	596,626
Total	582,641	596,793
Consumer and Other
Allowance For Loan Losses And Recorded Investment In Loans [Line Items]
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	57	74
Total ending allowance balance	57	74
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	4,769	5,568
Total	$ 4,769	$ 5,568

Allowance For Loan Losses And Recorded Investment In Loans Line Items.

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- Definition

The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

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- Definition

Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

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- Definition

Amount, before allowance for credit loss and fee, of financing receivable. Excludes financing receivable covered under loss sharing agreement.

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The balance of financing receivables that were collectively evaluated for impairment.

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The balance of financing receivables that were individually evaluated for impairment.

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- Definition

Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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