SEGMENT REPORTING - Reconciliation of Third Party Revenues to Direct Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Segment Reporting Information [Line Items]
Total revenues	$ 1,356,312	$ 926,458	$ 2,525,421	$ 1,734,606
Environmental Services
Segment Reporting Information [Line Items]
Total revenues	1,090,743	724,097	2,038,188	1,378,699
Safety-Kleen Sustainability Solutions
Segment Reporting Information [Line Items]
Total revenues	265,490	202,282	487,082	355,749
Operating Segments | Environmental Services
Segment Reporting Information [Line Items]
Total revenues	1,084,506	723,147	2,025,304	1,376,025
Operating Segments | Safety-Kleen Sustainability Solutions
Segment Reporting Information [Line Items]
Total revenues	271,727	203,232	499,966	358,423
Intersegment revenues, net | Environmental Services
Segment Reporting Information [Line Items]
Total revenues	6,237	950	12,884	2,674
Intersegment revenues, net | Safety-Kleen Sustainability Solutions
Segment Reporting Information [Line Items]
Total revenues	(6,237)	(950)	(12,884)	(2,674)
Corporate
Segment Reporting Information [Line Items]
Total revenues	$ 79	$ 79	$ 151	$ 158