Leases - Summary of Other Information Concerning the Company's Operating Lease (Detail) - USD ($)	Dec. 31, 2020	Oct. 09, 2020	Sep. 30, 2020	Aug. 28, 2020
Lessee, Lease, Description [Line Items]
Operating lease ROU asset included in other long-term assets	$ 970,000
Current operating lease liability	420,000		$ 328,000
Non-current operating lease liability	686,000		614,000
New Lease Agreement [Member]
Lessee, Lease, Description [Line Items]
Operating lease ROU asset included in other long-term assets		$ 254,000		$ 970,000
Blaw Knox Product Line From Volvo CE [Member] | New Lease Agreement [Member]
Lessee, Lease, Description [Line Items]
Operating lease ROU asset included in other long-term assets	1,106,000		942,000
Current operating lease liability	420,000		328,000
Non-current operating lease liability	$ 686,000		$ 614,000
Weighted average remaining lease term (in years)	2 years 9 months		2 years 11 months 1 day
Weighted average discount rate used in calculating ROU asset	4.00%		4.00%