Business Acquisitions - Summary of Elements of Purchase Price of Acquisitions (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Business Acquisition [Line Items]
Cash	$ 40,004	$ 175,450
Common Stock	6,020	25,000
Other Purchase Price Components Current	15,828	(1,889)
Contingent Consideration Current	1,000	34,661
Other Purchase Price Components Long Term		100
Contingent Consideration Long Term	6,004	10,543
Total Purchase Price	68,856	243,865
MSE Group
Business Acquisition [Line Items]
Cash	9,082
Common Stock	2,271
Other Purchase Price Components Current	10,280
Contingent Consideration Long Term	1,804
Total Purchase Price	23,437
Vista
Business Acquisition [Line Items]
Cash	9,025
Common Stock	475
Other Purchase Price Components Current	172
Contingent Consideration Long Term	1,000
Total Purchase Price	10,672
EI
Business Acquisition [Line Items]
Cash	15,397
Common Stock	2,274
Other Purchase Price Components Current	5,324
Total Purchase Price	22,995
Sensible
Business Acquisition [Line Items]
Cash	6,500
Common Stock	1,000
Other Purchase Price Components Current	52
Contingent Consideration Current	1,000
Contingent Consideration Long Term	3,200
Total Purchase Price	$ 11,752
CTEH
Business Acquisition [Line Items]
Cash		175,000
Common Stock		25,000
Other Purchase Price Components Current		(1,939)
Contingent Consideration Current		34,451
Contingent Consideration Long Term		10,543
Total Purchase Price		243,055
Other Acquisition
Business Acquisition [Line Items]
Cash		450
Other Purchase Price Components Current		50
Contingent Consideration Current		210
Other Purchase Price Components Long Term		100
Total Purchase Price		$ 810