Loans and Allowance for Loan Losses - Summary of Company's Loans by Risk Rating (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	$ 497,761	$ 489,305
Commercial Real Estate Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	146,930	143,893
Commercial Real Estate Loans [Member] | Pass [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	133,014	129,925
Commercial Real Estate Loans [Member] | Special Mention [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	8,154	9,257
Commercial Real Estate Loans [Member] | Substandard [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	5,762	4,711
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	23,869	20,259
Commercial and Industrial [Member] | Pass [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	23,459	19,828
Commercial and Industrial [Member] | Special Mention [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	410	431
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	8,724	10,289
Consumer [Member] | Note Rated [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	8,724	10,289
One-to-Four Family [Member] | Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	239,190	235,648
One-to-Four Family [Member] | Residential Real Estate [Member] | Note Rated [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	237,032	233,773
One-to-Four Family [Member] | Residential Real Estate [Member] | Special Mention [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	1,094	803
One-to-Four Family [Member] | Residential Real Estate [Member] | Substandard [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	1,064	1,072
Second Mortgages and HELOC [Member] | Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	49,073	48,166
Second Mortgages and HELOC [Member] | Residential Real Estate [Member] | Note Rated [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	48,690	47,582
Second Mortgages and HELOC [Member] | Residential Real Estate [Member] | Special Mention [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	383	584
Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	29,975	31,050
Construction [Member] | Pass [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	$ 29,975	$ 31,050