Allowance for Loan Losses - Allowance for Loan Losses (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of the period	$ 18,305	$ 17,071	$ 17,820	$ 16,394
Total loans charged-off	982	671	2,357	1,804
Total loan recoveries	257	222	857	830
Net loans charged-off	725	449	1,500	974
Total provision charged to operating expense	376	1,176	1,636	2,378
Balance at the end of the period	17,956	17,798	17,956	17,798
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off	224	206	640	219
Total loan recoveries	32	27	122	118
Total provision charged to operating expense	393	1,895	2,105	1,589
Commercial [Member] \| Owner Occupied Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off	9	97	346	110
Total loan recoveries	9	7	9	19
Commercial [Member] \| Non Owner Occupied Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off			64
Total loan recoveries	5	5	15	22
Commercial [Member] \| Residential Spec Homes [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off			3
Total loan recoveries	2	2	5	6
Commercial [Member] \| Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off	215	109	227	109
Total loan recoveries	16	13	93	71
Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off		2	48	17
Total loan recoveries	7	4	41	15
Total provision charged to operating expense	(289)	(243)	(185)	(612)
Real Estate [Member] \| Residential Mortgage [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off		2	48	17
Total loan recoveries	7	4	41	15
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off	758	463	1,669	1,568
Total loan recoveries	218	191	694	697
Total provision charged to operating expense	272	(476)	(284)	1,401
Consumer [Member] \| Direct Installment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off	69	20	134	124
Total loan recoveries	24	10	47	42
Consumer [Member] \| Indirect Installment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off	601	432	1,392	1,302
Total loan recoveries	129	107	512	378
Consumer [Member] \| Home Equity Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off	88	11	143	142
Total loan recoveries	$ 65	$ 74	$ 135	$ 277

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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