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, 2019	Dec. 31, 2018
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Federal income taxes at statutory rate, Amount	$ 92	$ (41)
State income taxes, net of federal income tax benefit, Amount		(34)
Increase in cash value of life insurance, Amount	(117)	(142)
Other, Amount	16	40
Credit for income taxes	$ (9)	$ (177)
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%	17.34%
Increase in cash value of life insurance, Percentage	(26.70%)	72.73%
Change in valuation allowance, Percentage	0.00%	0.00%
Other, Percentage	3.65%	(20.41%)
Provision (credit) for income taxes, Percentage	(2.05%)	90.66%