REVENUES - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Disaggregation of Revenue [Line Items]
Total revenues	$ 1,356,312	$ 926,458	$ 2,525,421	$ 1,734,606
Technical Services
Disaggregation of Revenue [Line Items]
Total revenues	387,019	306,865	710,675	578,905
Field and Emergency Response Services
Disaggregation of Revenue [Line Items]
Total revenues	144,860	106,986	277,219	212,154
Field and Emergency Response Services | HydroChemPSC
Disaggregation of Revenue [Line Items]
Total revenues	34,200		62,200
Industrial Services and Other
Disaggregation of Revenue [Line Items]
Total revenues	360,949	150,446	669,859	270,335
Industrial Services and Other | HydroChemPSC
Disaggregation of Revenue [Line Items]
Total revenues	173,700		329,800
Safety-Kleen Environmental Services
Disaggregation of Revenue [Line Items]
Total revenues	241,138	199,382	461,471	394,220
Safety-Kleen Oil
Disaggregation of Revenue [Line Items]
Total revenues	222,346	162,779	406,197	278,992
United States
Disaggregation of Revenue [Line Items]
Total revenues	1,182,537	796,880	2,219,817	1,511,457
Canada
Disaggregation of Revenue [Line Items]
Total revenues	173,775	129,578	305,604	223,149
Environmental Services
Disaggregation of Revenue [Line Items]
Total revenues	1,090,743	724,097	2,038,188	1,378,699
Safety-Kleen Sustainability Solutions
Disaggregation of Revenue [Line Items]
Total revenues	265,490	202,282	487,082	355,749
Operating segments | Environmental Services
Disaggregation of Revenue [Line Items]
Total revenues	1,084,506	723,147	2,025,304	1,376,025
Operating segments | Environmental Services | Technical Services
Disaggregation of Revenue [Line Items]
Total revenues	387,019	306,865	710,675	578,905
Operating segments | Environmental Services | Field and Emergency Response Services
Disaggregation of Revenue [Line Items]
Total revenues	144,860	106,986	277,219	212,154
Operating segments | Environmental Services | Industrial Services and Other
Disaggregation of Revenue [Line Items]
Total revenues	360,870	150,367	669,708	270,177
Operating segments | Environmental Services | Safety-Kleen Environmental Services
Disaggregation of Revenue [Line Items]
Total revenues	191,757	158,929	367,702	314,789
Operating segments | Environmental Services | Safety-Kleen Oil
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Operating segments | Environmental Services | United States
Disaggregation of Revenue [Line Items]
Total revenues	945,579	616,585	1,780,257	1,192,093
Operating segments | Environmental Services | Canada
Disaggregation of Revenue [Line Items]
Total revenues	138,927	106,562	245,047	183,932
Operating segments | Safety-Kleen Sustainability Solutions
Disaggregation of Revenue [Line Items]
Total revenues	271,727	203,232	499,966	358,423
Operating segments | Safety-Kleen Sustainability Solutions | Technical Services
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Operating segments | Safety-Kleen Sustainability Solutions | Field and Emergency Response Services
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Operating segments | Safety-Kleen Sustainability Solutions | Industrial Services and Other
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Operating segments | Safety-Kleen Sustainability Solutions | Safety-Kleen Environmental Services
Disaggregation of Revenue [Line Items]
Total revenues	49,381	40,453	93,769	79,431
Operating segments | Safety-Kleen Sustainability Solutions | Safety-Kleen Oil
Disaggregation of Revenue [Line Items]
Total revenues	222,346	162,779	406,197	278,992
Operating segments | Safety-Kleen Sustainability Solutions | United States
Disaggregation of Revenue [Line Items]
Total revenues	236,879	180,216	439,409	319,206
Operating segments | Safety-Kleen Sustainability Solutions | Canada
Disaggregation of Revenue [Line Items]
Total revenues	34,848	23,016	60,557	39,217
Corporate
Disaggregation of Revenue [Line Items]
Total revenues	79	79	151	158
Corporate | Technical Services
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Corporate | Field and Emergency Response Services
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Corporate | Industrial Services and Other
Disaggregation of Revenue [Line Items]
Total revenues	79	79	151	158
Corporate | Safety-Kleen Environmental Services
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Corporate | Safety-Kleen Oil
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Corporate | United States
Disaggregation of Revenue [Line Items]
Total revenues	79	79	151	158
Corporate | Canada
Disaggregation of Revenue [Line Items]
Total revenues	$ 0	$ 0	$ 0	$ 0