Goodwill & Intangibles - Additional Information (Detail) - USD ($) $ in Thousands		3 Months Ended
	Jul. 17, 2017	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Schedule Of Goodwill And Intangible Assets [Line Items]
Goodwill		$ 1,702		$ 1,702
General and Administrative Expense [Member]
Schedule Of Goodwill And Intangible Assets [Line Items]
Intangible asset amortization		$ 17	$ 17
Customer Relationships [Member]
Schedule Of Goodwill And Intangible Assets [Line Items]
Amortization period of intangible assets		4 years
Comstock Environmental [Member]
Schedule Of Goodwill And Intangible Assets [Line Items]
Purchase price of business assets	$ 2,300