Allowance for Loan Losses - Summary of Allowance for Loan Losses (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Allowance for loan losses:
Allowance for loan losses, beginning of year	$ 23,075	$ 22,318	$ 20,941
Charge-offs	(389)	(781)	(1,382)
Recoveries	434	1,338	709
Reclassification to other liabilities	(89)
Provision	1,375	200
Allowance for loan losses, end of year	24,406	23,075	22,318
Amount of allowance for loan losses for loans deemed to be impaired	173	250
Amount of allowance for loan losses for loans not deemed to be impaired	24,233	22,825
Loans:
Total loans, net	1,923,933	1,731,536
Loans deemed to be impaired	3,830	3,225	6,327
Loans not deemed to be impaired	1,920,103	1,728,311
Construction and Land Development [Member]
Allowance for loan losses:
Allowance for loan losses, beginning of year	2,041	1,592
Recoveries		780
Reclassification to other liabilities	(5)
Provision	(1,024)	(331)
Allowance for loan losses, end of year	1,012	2,041	1,592
Amount of allowance for loan losses for loans deemed to be impaired	3	10
Amount of allowance for loan losses for loans not deemed to be impaired	1,009	2,031
Loans:
Total loans, net	14,928	27,421
Loans deemed to be impaired	94	98
Loans not deemed to be impaired	14,834	27,323
Commercial and Industrial [Member]
Allowance for loan losses:
Allowance for loan losses, beginning of year	5,899	4,757
Charge-offs		(172)
Recoveries	132	212
Reclassification to other liabilities	(25)
Provision	966	1,102
Allowance for loan losses, end of year	6,972	5,899	4,757
Amount of allowance for loan losses for loans deemed to be impaired	23	19
Amount of allowance for loan losses for loans not deemed to be impaired	6,949	5,880
Loans:
Total loans, net	612,503	452,235
Loans deemed to be impaired	389	443
Loans not deemed to be impaired	612,114	451,792
Municipal [Member]
Allowance for loan losses:
Allowance for loan losses, beginning of year	994	1,488
Provision	618	(494)
Allowance for loan losses, end of year	1,612	994	1,488
Amount of allowance for loan losses for loans not deemed to be impaired	1,612	994
Loans:
Total loans, net	135,418	85,685
Loans not deemed to be impaired	135,418	85,685
Commercial Real Estate [Member]
Allowance for loan losses:
Allowance for loan losses, beginning of year	10,589	11,199
Charge-offs		(298)
Recoveries		84
Reclassification to other liabilities	(9)
Provision	555	(396)
Allowance for loan losses, end of year	11,135	10,589	11,199
Amount of allowance for loan losses for loans deemed to be impaired	140	99
Amount of allowance for loan losses for loans not deemed to be impaired	10,995	10,490
Loans:
Total loans, net	696,173	721,506
Loans deemed to be impaired	3,149	1,678
Loans not deemed to be impaired	693,024	719,828
Residential Real Estate [Member]
Allowance for loan losses:
Allowance for loan losses, beginning of year	1,320	776
Recoveries	6	7
Reclassification to other liabilities	(3)
Provision	375	537
Allowance for loan losses, end of year	1,698	1,320	776
Amount of allowance for loan losses for loans deemed to be impaired	7	32
Amount of allowance for loan losses for loans not deemed to be impaired	1,691	1,288
Loans:
Total loans, net	241,357	255,346
Loans deemed to be impaired	198	916
Loans not deemed to be impaired	241,159	254,430
Consumer [Member]
Allowance for loan losses:
Allowance for loan losses, beginning of year	644	810
Charge-offs	(362)	(311)
Recoveries	296	255
Reclassification to other liabilities	(3)
Provision	7	(110)
Allowance for loan losses, end of year	582	644	810
Amount of allowance for loan losses for loans not deemed to be impaired	582	644
Loans:
Total loans, net	11,697	11,323
Loans not deemed to be impaired	11,697	11,323
Home Equity [Member]
Allowance for loan losses:
Allowance for loan losses, beginning of year	1,077	599
Charge-offs	(27)
Reclassification to other liabilities	(44)
Provision	96	478
Allowance for loan losses, end of year	1,102	1,077	599
Amount of allowance for loan losses for loans deemed to be impaired		90
Amount of allowance for loan losses for loans not deemed to be impaired	1,102	987
Loans:
Total loans, net	211,857	178,020
Loans deemed to be impaired		90
Loans not deemed to be impaired	211,857	177,930
Unallocated [Member]
Allowance for loan losses:
Allowance for loan losses, beginning of year	511	1,097
Provision	(218)	(586)
Allowance for loan losses, end of year	293	511	$ 1,097
Amount of allowance for loan losses for loans not deemed to be impaired	$ 293	$ 511

Amount of allowance for loans losses for loans not deemed to be impaired.

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Provision for loan losses gains expensed.

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Reclassification of other liabilities.

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

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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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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The recorded amount of loans and debt securities, with evidence of deterioration of credit quality since origination that were acquired by completion of a transfer for which it was probable, at acquisition, that the investor would be unable to collect all contractually required payments receivable, but which are not deemed to be impaired since the acquisition by transfer. Therefore, no allowance for credit losses is recorded.

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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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Amount of allowance for credit losses related to recorded investment.

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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 before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

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