Allowance for Loan Losses - Allowance for Loan Losses (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of the period	$ 17,821	$ 16,474	$ 17,820	$ 16,394
Total loans charged-off	714	417	1,375	1,133
Total loan recoveries	302	379	600	608
Net loans charged-off	412	38	775	525
Total provision charged to operating expense	896	635	1,260	1,202
Balance at the end of the period	18,305	17,071	18,305	17,071
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off	339		416	13
Total loan recoveries	74	40	90	91
Total provision charged to operating expense	590	985	1,712	(306)
Commercial [Member] \| Owner Occupied Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off	336		337	13
Total loan recoveries				12
Commercial [Member] \| Non Owner Occupied Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off			64
Total loan recoveries	4	12	10	17
Commercial [Member] \| Residential Spec Homes [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off	3		3
Total loan recoveries	1	2	3	4
Commercial [Member] \| Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off			12
Total loan recoveries	69	26	77	58
Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off	48	3	48	15
Total loan recoveries	7	5	34	11
Total provision charged to operating expense	211	(117)	104	(369)
Real Estate [Member] \| Residential Mortgage [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off	48	3	48	15
Total loan recoveries	7	5	34	11
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off	327	414	911	1,105
Total loan recoveries	221	334	476	506
Total provision charged to operating expense	95	(233)	(556)	1,877
Consumer [Member] \| Direct Installment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off	37	49	65	104
Total loan recoveries	75	21	86	32
Consumer [Member] \| Indirect Installment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off	251	365	791	870
Total loan recoveries	182	132	383	271
Consumer [Member] \| Home Equity Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off	39		55	131
Total loan recoveries	$ (36)	$ 181	$ 7	$ 203

Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

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Amount, after recoveries, of loans and leases that have been written-off.

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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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Amount of expense related to estimated loss from loan and lease transactions.

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