Revenue - Schedule of Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Total revenue	$ 118,715	$ 121,113	$ 416,491	$ 405,307
Unapproved change orders	2,459		2,459
Approved change orders	909		909
Environmental Solutions
Disaggregation of Revenue [Line Items]
Total revenue	45,800	46,013	120,327	141,346
Environmental Solutions | United States
Disaggregation of Revenue [Line Items]
Total revenue	45,729	46,013	119,410	141,346
Environmental Solutions | Foreign
Disaggregation of Revenue [Line Items]
Total revenue	71	0	917	0
Maintenance and Technical Services
Disaggregation of Revenue [Line Items]
Total revenue	72,915	75,100	296,164	263,961
Maintenance and Technical Services | United States
Disaggregation of Revenue [Line Items]
Total revenue	72,915	75,100	296,164	263,961
Product sales | Environmental Solutions
Disaggregation of Revenue [Line Items]
Total revenue	22,940	28,995	66,101	76,397
Construction contracts | Environmental Solutions
Disaggregation of Revenue [Line Items]
Total revenue	21,590	16,841	51,784	63,048
Services | Environmental Solutions
Disaggregation of Revenue [Line Items]
Total revenue	1,270	177	2,442	1,901
Services | Maintenance and Technical Services
Disaggregation of Revenue [Line Items]
Total revenue	$ 72,915	$ 75,100	$ 296,164	$ 263,961