SEGMENT REPORTING - Reconciliation to Consolidated Statements of Income to Adjusted EBITDA (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Segment Reporting Information [Line Items]
Adjusted EBITDA	$ 180,259	$ 129,451
Reconciliation to Consolidated Statements of Operations:
Accretion of environmental liabilities	3,156	2,953
Stock-based compensation	5,712	3,480
Depreciation and amortization	84,298	72,163
Income from operations	87,093	50,855
Other (income) expense, net	(704)	1,228
Interest expense, net of interest income	25,017	17,918
Income before provision for income taxes	62,780	31,709
Operating segments | Environmental Services
Segment Reporting Information [Line Items]
Adjusted EBITDA	183,602	140,254
Operating segments | Safety-Kleen Sustainability Solutions
Segment Reporting Information [Line Items]
Adjusted EBITDA	51,877	31,632
Corporate
Segment Reporting Information [Line Items]
Adjusted EBITDA	$ (55,220)	$ (42,435)