Allowance for Loan Losses - Summary of Allowance for Loan Losses (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Allowance for Loan Losses:
Allowance for loan losses, beginning of period	$ 34,949	$ 32,516	$ 35,486	$ 29,585
Charge-offs	(38)	(41)	(134)	(120)
Recoveries	53	19	162	254
Provision (credit)	(200)	900	(750)	3,675
Allowance for loan losses, end of period	34,764	33,394	34,764	33,394
Amount of allowance for loan losses for loans deemed to be impaired	81	87	81	87
Amount of allowance for loan losses for loans not deemed to be impaired	34,683	33,307	34,683	33,307
Loans:
Total loans, net	2,925,477	2,990,133	2,925,477	2,990,133	$ 2,995,829
Loans deemed to be impaired	2,316	3,071	2,316	3,071
Loans not deemed to be impaired	2,923,161	2,987,062	2,923,161	2,987,062
Construction and Land Development [Member]
Allowance for Loan Losses:
Allowance for loan losses, beginning of period	220	289	429	331
Provision (credit)	(3)	76	(212)	34
Allowance for loan losses, end of period	217	365	217	365
Amount of allowance for loan losses for loans not deemed to be impaired	217	365	217	365
Loans:
Total loans, net	6,358	9,116	6,358	9,116	10,909
Loans not deemed to be impaired	6,358	9,116	6,358	9,116
Commercial and Industrial [Member]
Allowance for Loan Losses:
Allowance for loan losses, beginning of period	16,502	13,121	16,713	11,596
Charge-offs		(20)		(31)
Recoveries	30	12	35	182
Provision (credit)	1,134	2,731	918	4,097
Allowance for loan losses, end of period	17,666	15,844	17,666	15,844
Amount of allowance for loan losses for loans deemed to be impaired	10	12	10	12
Amount of allowance for loan losses for loans not deemed to be impaired	17,656	15,832	17,656	15,832
Loans:
Total loans, net	1,321,907	1,315,407	1,321,907	1,315,407	1,314,245
Loans deemed to be impaired	77	160	77	160
Loans not deemed to be impaired	1,321,830	1,315,247	1,321,830	1,315,247
Municipal [Member]
Allowance for Loan Losses:
Allowance for loan losses, beginning of period	2,817	2,868	2,804	2,566
Provision (credit)	(11)	(300)	2	2
Allowance for loan losses, end of period	2,806	2,568	2,806	2,568
Amount of allowance for loan losses for loans not deemed to be impaired	2,806	2,568	2,806	2,568
Loans:
Total loans, net	138,945	130,047	138,945	130,047	137,607
Loans not deemed to be impaired	138,945	130,047	138,945	130,047
Commercial Real Estate [Member]
Allowance for Loan Losses:
Allowance for loan losses, beginning of period	11,708	11,303	11,751	11,464
Provision (credit)	(1,137)	(522)	(1,180)	(683)
Allowance for loan losses, end of period	10,571	10,781	10,571	10,781
Amount of allowance for loan losses for loans deemed to be impaired	71	75	71	75
Amount of allowance for loan losses for loans not deemed to be impaired	10,500	10,706	10,500	10,706
Loans:
Total loans, net	729,384	784,895	729,384	784,895	789,836
Loans deemed to be impaired	2,239	2,675	2,239	2,675
Loans not deemed to be impaired	727,145	782,220	727,145	782,220
Residential Real Estate [Member]
Allowance for Loan Losses:
Allowance for loan losses, beginning of period	2,029	3,094	2,111	2,194
Provision (credit)	(67)	(958)	(149)	(58)
Allowance for loan losses, end of period	1,962	2,136	1,962	2,136
Amount of allowance for loan losses for loans not deemed to be impaired	1,962	2,136	1,962	2,136
Loans:
Total loans, net	466,109	443,703	466,109	443,703	448,436
Loans deemed to be impaired		236		236
Loans not deemed to be impaired	466,109	443,467	466,109	443,467
Consumer [Member]
Allowance for Loan Losses:
Allowance for loan losses, beginning of period	204	289	241	312
Charge-offs	(38)	(21)	(134)	(89)
Recoveries	23	7	127	67
Provision (credit)	10	35	(35)	20
Allowance for loan losses, end of period	199	310	199	310
Amount of allowance for loan losses for loans not deemed to be impaired	199	310	199	310
Loans:
Total loans, net	19,549	19,866	19,549	19,866	20,439
Loans not deemed to be impaired	19,549	19,866	19,549	19,866
Home Equity [Member]
Allowance for Loan Losses:
Allowance for loan losses, beginning of period	957	1,465	1,208	1,065
Recoveries				5
Provision (credit)	(58)	(200)	(309)	195
Allowance for loan losses, end of period	899	1,265	899	1,265
Amount of allowance for loan losses for loans not deemed to be impaired	899	1,265	899	1,265
Loans:
Total loans, net	243,225	287,099	243,225	287,099	$ 274,357
Loans not deemed to be impaired	243,225	287,099	243,225	287,099
Unallocated [Member]
Allowance for Loan Losses:
Allowance for loan losses, beginning of period	512	87	229	57
Provision (credit)	(68)	38	215	68
Allowance for loan losses, end of period	444	125	444	125
Amount of allowance for loan losses for loans not deemed to be impaired	$ 444	$ 125	$ 444	$ 125

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

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- Definition

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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