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

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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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Amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

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Allowance for Loan Losses - Allowance for Loan Losses and Recorded Investment in Loans by Portfolio Segment (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Allowance for Credit Losses [Line Items]
Total ending allowance balance	$ 17,821	$ 17,820	$ 16,474	$ 16,394
Total ending loans balance	6,233		$ 6,824
Allowance for Loan Losses [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance For Loan Losses, Individually evaluated for impairment	915	1,035
Allowance For Loan Losses, Collectively evaluated for impairment	16,906	16,785
Total ending allowance balance	17,821	17,820
Commercial [Member] \| Allowance for Loan Losses [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance For Loan Losses, Individually evaluated for impairment	915	1,035
Allowance For Loan Losses, Collectively evaluated for impairment	10,641	9,460
Total ending allowance balance	11,556	10,495
Real Estate [Member] \| Allowance for Loan Losses [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance For Loan Losses, Collectively evaluated for impairment	1,588	1,676
Total ending allowance balance	1,588	1,676
Consumer [Member] \| Allowance for Loan Losses [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance For Loan Losses, Collectively evaluated for impairment	3,663	4,643
Total ending allowance balance	3,663	4,643
Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans: Individually evaluated for impairment	6,233	6,708
Loans: Collectively evaluated for impairment	3,617,928	3,010,063
Total ending loans balance	3,624,161	3,016,771
Loans [Member] \| Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans: Individually evaluated for impairment	6,233	6,708
Loans: Collectively evaluated for impairment	2,087,011	1,718,661
Total ending loans balance	2,093,244	1,725,369
Loans [Member] \| Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans: Collectively evaluated for impairment	821,767	670,166
Total ending loans balance	821,767	670,166
Loans [Member] \| Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans: Collectively evaluated for impairment	637,206	547,116
Total ending loans balance	637,206	547,116
Mortgage Warehousing [Member] \| Allowance for Loan Losses [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance For Loan Losses, Collectively evaluated for impairment	1,014	1,006
Total ending allowance balance	1,014	1,006
Mortgage Warehousing [Member] \| Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans: Collectively evaluated for impairment	71,944	74,120
Total ending loans balance	$ 71,944	$ 74,120