Allowance for Loan Losses - Allowance for Loan Losses (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of the period	$ 15,027	$ 14,226	$ 14,837	$ 14,534
Total loans charged-off	663	406	1,683	2,108
Total loan recoveries	512	249	1,062	879
Net loans charged-off (recovered)	151	157	621	1,229
Total provision charged to operating expense	710	455	1,370	1,219
Balance at the end of the period	15,586	14,524	15,586	14,524
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off	264	11	306	700
Total loan recoveries	95	17	247	199
Total provision charged to operating expense	429	165	1,357	(471)
Commercial [Member] \| Owner Occupied Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off	12	4	12	182
Total loan recoveries	7	2	8	31
Commercial [Member] \| Non Owner Occupied Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off	20	(1)	20	471
Total loan recoveries	4	1	29	55
Commercial [Member] \| Residential Development [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loan recoveries	2	2	6	6
Commercial [Member] \| Development & Spec Land Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off			1
Commercial [Member] \| Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off	232	8	273	47
Total loan recoveries	82	12	204	107
Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off	37	12	89	127
Total loan recoveries	13	12	35	75
Total provision charged to operating expense	361	102	(113)	(147)
Real Estate [Member] \| Residential Mortgage [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off	37	12	89	127
Total loan recoveries	13	12	35	75
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off	362	383	1,288	1,281
Total loan recoveries	404	220	780	605
Total provision charged to operating expense	(80)	188	126	1,837
Consumer [Member] \| Direct Installment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off	84	55	331	159
Total loan recoveries	260	26	311	70
Consumer [Member] \| Indirect Installment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off	254	296	862	851
Total loan recoveries	119	160	384	400
Consumer [Member] \| Home Equity Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans charged-off	24	32	95	271
Total loan recoveries	$ 25	$ 34	$ 85	$ 135

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.

+ References

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

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