REVENUES (Narrative) (Details)	3 Months Ended
	Mar. 31, 2021 source
Disaggregation of Revenue [Line Items]
Deferred contract cost, recognition period	3 months
Environmental Services
Disaggregation of Revenue [Line Items]
Number of revenue sources	4
Safety-Kleen Sustainability Solutions
Disaggregation of Revenue [Line Items]
Number of revenue sources	2