Loans and Allowance for Loan Losses - Summary of Activity in the Allowance for Loan Losses by Loan Category (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	$ 6,784	$ 4,280
Provision (credit) for loan losses	(213)	724
Loans charged-off	(10)	(16)
Recoveries	2	8
Ending balance	6,563	4,996
Commercial Real Estate Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	3,402	1,840
Provision (credit) for loan losses	(12)	401
Ending balance	3,390	2,241
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	416	235
Provision (credit) for loan losses	(15)	45
Ending balance	401	280
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	127	128
Provision (credit) for loan losses	(12)	21
Loans charged-off	(10)	(16)
Recoveries		4
Ending balance	105	137
One-to-Four Family [Member] \| Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	1,646	1,096
Provision (credit) for loan losses	(126)	123
Recoveries	2	4
Ending balance	1,522	1,223
Second Mortgages and HELOC [Member] \| Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	442	289
Provision (credit) for loan losses	(17)	54
Ending balance	425	343
Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	751	692
Provision (credit) for loan losses	(31)	80
Ending balance	$ 720	$ 772

Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

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