SEGMENT REPORTING - Reconciliation to Consolidated Statements of Income to Adjusted EBITDA (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Segment Reporting Information [Line Items]
Adjusted EBITDA	$ 287,506		$ 309,070	$ 502,644	$ 489,329
Reconciliation to Consolidated Statements of Operations:
Accretion of environmental liabilities	3,486		3,197	6,893	6,353
Stock-based compensation	4,500		6,835	10,518	12,547
Depreciation and amortization	89,697		87,868	174,455	172,166
Income from operations	189,823		211,170	310,778	298,263
Other expense (income), net	1,283		(1,265)	1,167	(1,969)
Loss on early extinguishment of debt	0	$ 2,400	0	2,362	0
Gain on sale of business	0		(8,864)	0	(8,864)
Interest expense, net of interest income	30,072		26,256	50,704	51,273
Income before provision for income taxes	158,468		195,043	256,545	257,823
Operating Segments | Environmental Services
Segment Reporting Information [Line Items]
Adjusted EBITDA	305,622		269,341	533,967	452,943
Operating Segments | Safety-Kleen Sustainability Solutions
Segment Reporting Information [Line Items]
Adjusted EBITDA	53,415		97,010	94,878	148,887
Corporate
Segment Reporting Information [Line Items]
Adjusted EBITDA	$ (71,531)		$ (57,281)	$ (126,201)	$ (112,501)