Allowance for Loan Losses - Summary of Allowance for Loan Losses (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Allowance for Loan Losses:
Allowance for loan losses, beginning of year	$ 28,543	$ 26,255	$ 24,406
Charge-offs	(454)	(833)	(390)
Recoveries	246	1,771	449
Provision	1,250	1,350
Allowance for loan losses, end of year	29,585	28,543	26,255
Amount of allowance for loan losses for loans deemed to be impaired	102	145
Amount of allowance for loan losses for loans not deemed to be impaired	29,483	28,398
Loans:
Total loans, net	2,426,119	2,285,578
Loans deemed to be impaired	3,252	3,051	7,114
Loans not deemed to be impaired	2,422,867	2,282,527
Construction and Land Development [Member]
Allowance for Loan Losses:
Allowance for loan losses, beginning of year	1,092	1,645
Recoveries		1,436
Provision	(761)	(1,989)
Allowance for loan losses, end of year	331	1,092	1,645
Amount of allowance for loan losses for loans not deemed to be impaired	331	1,092
Loans:
Total loans, net	8,992	13,628
Loans not deemed to be impaired	8,992	13,628
Commercial and Industrial [Member]
Allowance for Loan Losses:
Allowance for loan losses, beginning of year	10,998	9,651
Charge-offs	(137)	(67)
Recoveries	60	57
Provision	675	1,357
Allowance for loan losses, end of year	11,596	10,998	9,651
Amount of allowance for loan losses for loans deemed to be impaired	15	54
Amount of allowance for loan losses for loans not deemed to be impaired	11,581	10,944
Loans:
Total loans, net	812,417	761,625
Loans deemed to be impaired	906	401
Loans not deemed to be impaired	811,511	761,224
Municipal [Member]
Allowance for Loan Losses:
Allowance for loan losses, beginning of year	1,838	1,720
Provision	728	118
Allowance for loan losses, end of year	2,566	1,838	1,720
Amount of allowance for loan losses for loans not deemed to be impaired	2,566	1,838
Loans:
Total loans, net	120,455	97,290
Loans not deemed to be impaired	120,455	97,290
Commercial Real Estate [Member]
Allowance for Loan Losses:
Allowance for loan losses, beginning of year	10,663	9,728
Provision	801	935
Allowance for loan losses, end of year	11,464	10,663	9,728
Amount of allowance for loan losses for loans deemed to be impaired	87	91
Amount of allowance for loan losses for loans not deemed to be impaired	11,377	10,572
Loans:
Total loans, net	786,102	750,362
Loans deemed to be impaired	2,346	2,650
Loans not deemed to be impaired	783,756	747,712
Residential Real Estate [Member]
Allowance for Loan Losses:
Allowance for loan losses, beginning of year	2,190	1,873
Charge-offs		(450)
Recoveries		75
Provision	4	692
Allowance for loan losses, end of year	2,194	2,190	1,873
Amount of allowance for loan losses for loans not deemed to be impaired	2,194	2,190
Loans:
Total loans, net	371,897	348,250
Loans not deemed to be impaired	371,897	348,250
Consumer [Member]
Allowance for Loan Losses:
Allowance for loan losses, beginning of year	365	373
Charge-offs	(295)	(316)
Recoveries	186	203
Provision	56	105
Allowance for loan losses, end of year	312	365	373
Amount of allowance for loan losses for loans not deemed to be impaired	312	365
Loans:
Total loans, net	21,893	22,083
Loans not deemed to be impaired	21,893	22,083
Home Equity [Member]
Allowance for Loan Losses:
Allowance for loan losses, beginning of year	1,111	989
Charge-offs	(22)
Provision	(24)	122
Allowance for loan losses, end of year	1,065	1,111	989
Amount of allowance for loan losses for loans not deemed to be impaired	1,065	1,111
Loans:
Total loans, net	304,363	292,340
Loans not deemed to be impaired	304,363	292,340
Unallocated [Member]
Allowance for Loan Losses:
Allowance for loan losses, beginning of year	286	276
Provision	(229)	10
Allowance for loan losses, end of year	57	286	$ 276
Amount of allowance for loan losses for loans not deemed to be impaired	$ 57	$ 286

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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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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