SEGMENT REPORTING - Reconciliation to Consolidated Statements of Income to Adjusted EBITDA (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Segment Reporting Information [Line Items]
Adjusted EBITDA	$ 308,555	$ 185,084	$ 797,884	$ 502,306
Reconciliation to Consolidated Statements of Operations:
Accretion of environmental liabilities	3,246	2,799	9,599	8,625
Stock-based compensation	7,828	6,001	20,375	12,786
Depreciation and amortization	88,394	71,451	260,560	215,206
Income from operations	209,087	104,833	507,350	265,689
Other (income) expense, net	(104)	(199)	(2,073)	2,509
Gain on sale of business	0	0	(8,864)	0
Interest expense, net of interest income	28,081	17,984	79,354	53,953
Income before provision for income taxes	181,110	87,048	438,933	209,227
Operating segments | Environmental Services
Segment Reporting Information [Line Items]
Adjusted EBITDA	260,687	166,471	713,630	482,766
Operating segments | Safety-Kleen Sustainability Solutions
Segment Reporting Information [Line Items]
Adjusted EBITDA	103,156	70,810	252,043	165,756
Corporate
Segment Reporting Information [Line Items]
Adjusted EBITDA	$ (55,288)	$ (52,197)	$ (167,789)	$ (146,216)