Goodwill and Intangible Assets - Schedule of Amounts Related to Goodwill (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2021 USD ($)
Goodwill [Line Items]
Balance	$ 274,667
Goodwill acquired during the period	29,570
Balance	304,237
Assessment, Permitting and Response
Goodwill [Line Items]
Balance	162,156
Goodwill acquired during the period	8,944
Balance	171,100
Measurement and Analysis
Goodwill [Line Items]
Balance	69,054
Goodwill acquired during the period	12,879
Balance	81,933
Remediation and Reuse Segment
Goodwill [Line Items]
Balance	43,457
Goodwill acquired during the period	7,747
Balance	$ 51,204