REVENUES - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Disaggregation of Revenue [Line Items]
Total revenues	$ 1,307,387	$ 1,169,109
Technical Services
Disaggregation of Revenue [Line Items]
Total revenues	366,509	323,656
Industrial Services and Other
Disaggregation of Revenue [Line Items]
Total revenues	336,486	308,910
Field and Emergency Response Services
Disaggregation of Revenue [Line Items]
Total revenues	148,086	132,359
Safety-Kleen Environmental Services
Disaggregation of Revenue [Line Items]
Total revenues	259,567	220,333
Safety-Kleen Oil
Disaggregation of Revenue [Line Items]
Total revenues	196,739	183,851
United States
Disaggregation of Revenue [Line Items]
Total revenues	1,180,462	1,037,280
Canada
Disaggregation of Revenue [Line Items]
Total revenues	126,925	131,829
Environmental Services
Disaggregation of Revenue [Line Items]
Total revenues	1,070,741	947,445
Safety-Kleen Sustainability Solutions
Disaggregation of Revenue [Line Items]
Total revenues	236,539	221,592
Operating Segments | Environmental Services
Disaggregation of Revenue [Line Items]
Total revenues	1,060,982	940,798
Operating Segments | Environmental Services | Technical Services
Disaggregation of Revenue [Line Items]
Total revenues	366,509	323,656
Operating Segments | Environmental Services | Industrial Services and Other
Disaggregation of Revenue [Line Items]
Total revenues	336,379	308,838
Operating Segments | Environmental Services | Field and Emergency Response Services
Disaggregation of Revenue [Line Items]
Total revenues	148,086	132,359
Operating Segments | Environmental Services | Safety-Kleen Environmental Services
Disaggregation of Revenue [Line Items]
Total revenues	210,008	175,945
Operating Segments | Environmental Services | Safety-Kleen Oil
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Operating Segments | Environmental Services | United States
Disaggregation of Revenue [Line Items]
Total revenues	958,584	834,678
Operating Segments | Environmental Services | Canada
Disaggregation of Revenue [Line Items]
Total revenues	102,398	106,120
Operating Segments | Safety-Kleen Sustainability Solutions
Disaggregation of Revenue [Line Items]
Total revenues	246,298	228,239
Operating Segments | Safety-Kleen Sustainability Solutions | Technical Services
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Operating Segments | Safety-Kleen Sustainability Solutions | Industrial Services and Other
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Operating Segments | Safety-Kleen Sustainability Solutions | Field and Emergency Response Services
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Operating Segments | Safety-Kleen Sustainability Solutions | Safety-Kleen Environmental Services
Disaggregation of Revenue [Line Items]
Total revenues	49,559	44,388
Operating Segments | Safety-Kleen Sustainability Solutions | Safety-Kleen Oil
Disaggregation of Revenue [Line Items]
Total revenues	196,739	183,851
Operating Segments | Safety-Kleen Sustainability Solutions | United States
Disaggregation of Revenue [Line Items]
Total revenues	221,771	202,530
Operating Segments | Safety-Kleen Sustainability Solutions | Canada
Disaggregation of Revenue [Line Items]
Total revenues	24,527	25,709
Corporate
Disaggregation of Revenue [Line Items]
Total revenues	107	72
Corporate | Technical Services
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Corporate | Industrial Services and Other
Disaggregation of Revenue [Line Items]
Total revenues	107	72
Corporate | Field and Emergency Response Services
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Corporate | Safety-Kleen Environmental Services
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Corporate | Safety-Kleen Oil
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Corporate | United States
Disaggregation of Revenue [Line Items]
Total revenues	107	72
Corporate | Canada
Disaggregation of Revenue [Line Items]
Total revenues	$ 0	$ 0