Discontinued Operations - Summary of Gain on Sale of Discontinued Operations (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Discontinued Operations And Disposal Groups [Abstract]
Indemnification escrow proceeds				$ 862,000
Costs incurred related to environmental remediation				359,000
Gain from discontinued operations before income taxes				503,000
Income tax expense (benefit):
Current	$ (24,000)	$ (49,000)	$ (52,000)	137,000
Deferred	$ 24,000	$ 49,000	$ 52,000	(37,000)
Income tax (benefit) from discontinued operation				100,000
Gain from discontinued operations, net of taxes				$ 403,000