Income Taxes - Summary of the Sources of Differences Between Income Taxes At the Federal Statutory Rate and the Provision (Credit) for Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Federal income taxes at statutory rate, Amount	$ 641	$ 92
State income taxes, net of federal income tax benefit, Amount
Increase in cash value of life insurance, Amount	(84)	(117)
Change in valuation allowance, Amount	934
Other, Amount	245	16
Provision (credit) for income taxes	$ 1,736	$ (9)
Reconciliation of statutory to effective rates: Percentage
Federal income taxes at statutory rate, Percentage	21.00%	21.00%
State income taxes, net of federal income tax benefit, Percentage	0.00%	0.00%
Increase in cash value of life insurance, Percentage	(2.75%)	(26.70%)
Change in valuation allowance, Percentage	30.60%	0.00%
Other, Percentage	8.03%	3.65%
Provision (credit) for income taxes, Percentage	56.88%	(2.05%)