Allowances for Loan Losses - Additional Information (Detail) $ in Thousands	9 Months Ended	10 Months Ended	12 Months Ended
Sep. 30, 2021 USD ($) Loans	Dec. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)
Loans and Leases Receivable Disclosure [Line Items]
Purchased loans acquired with deteriorated credit quality	$ 5,385
Unpaid principal balance	170	$ 292	$ 292
Non accrual loans recorded investment	416	469	469
Total Loans	668,672	236,840	236,840
Federal Home Loan Bank (FHLB) [Member]
Loans and Leases Receivable Disclosure [Line Items]
Borrowings secured by loans pledged to FHLB	0	1,120	1,120
Real Estate Commercial Loans And Construction And Development [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	$ 309,079
Loan portfolio percentage	46.20%
Commercial Real Estate Portfolio Segment [Member]
Loans and Leases Receivable Disclosure [Line Items]
Purchased loans acquired with deteriorated credit quality	$ 3,467
Unpaid principal balance	0	0	0
Non accrual loans recorded investment	0	0	0
Total Loans	309,079	$ 27,261	$ 27,261
Purchased Credit Impaired Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Purchased loans acquired with deteriorated credit quality	5,384
Unpaid principal balance	6,627
Estimated fair value of loans	5,384
Contractual principal and interest at merger	8,509
Preliminary estimate of expected cash flows	5,793
Established credit risk related non-accretable discount	2,716
Accretable discount	409
Covid -19 [Member] \| Small Business Administration (SBA) [Member]
Loans and Leases Receivable Disclosure [Line Items]
Maximum overdue period for a loan modification not to be classfied as troubled debt restructuring			30 days
Maximum period within which the loan must have been executed from the date of declaration of national emergency		60 days
Loan receivable for which payment has been deferred	$ 8,558
Number of loans deferred \| Loans	3
Owner Occupied [Member] \| Commercial Real Estate Portfolio Segment [Member]
Loans and Leases Receivable Disclosure [Line Items]
Mortgage loans on real estate	$ 83,334

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Financing receivable loans acquired with deteriorated credit quality.

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Loan portfolio percentage.

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Maximum period within which the loan must have been executed from the date of declaration of national emergency.

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