Acquisition - Schedule of Estimated Fair Values of Assets Acquired and Liabilities Assumed (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Jul. 31, 2020	Jun. 04, 2020	Dec. 31, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Goodwill	$ 161,352			$ 152,020	$ 152,156
Mader Holdings L.P. | Joint Venture Agreement
Business Acquisition [Line Items]
Current assets		$ 2,040
Property and equipment		103
Goodwill		2,000
Total assets acquired		4,430
Current liabilities assumed		(430)
Deferred income tax asset		287
Other liabilities		(500)
Long term debt		(2,508)
Fair value of 30% noncontrolling equity interest in Mader		$ 992
Environmental Integrated Solutions [Member]
Business Acquisition [Line Items]
Current assets			$ 6,416
Property and equipment			26
Other assets			44
Goodwill			7,022
Intangible - finite life			4,840
Total assets acquired			18,348
Current liabilities assumed			(6,514)
Deferred income tax liability			(920)
Net assets acquired			$ 10,914