GOODWILL AND OTHER INTANGIBLE ASSETS - Changes to Goodwill (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2022 USD ($)
Goodwill [Roll Forward]
Balance at January 1, 2022	$ 1,227,042
Measurement period adjustments from prior period acquisitions	(6,557)
Foreign currency translation	914
Balance at March 31, 2022	1,221,399
Environmental Services
Goodwill [Roll Forward]
Balance at January 1, 2022	1,085,534
Measurement period adjustments from prior period acquisitions	(6,557)
Foreign currency translation	671
Balance at March 31, 2022	1,079,648
Safety-Kleen Sustainability Solutions
Goodwill [Roll Forward]
Balance at January 1, 2022	141,508
Measurement period adjustments from prior period acquisitions	0
Foreign currency translation	243
Balance at March 31, 2022	$ 141,751