GOODWILL AND OTHER INTANGIBLE ASSETS - Rollforward of Goodwill (Details) $ in Thousands	9 Months Ended
Sep. 30, 2020 USD ($)
Goodwill [Roll Forward]
Balance at January 1, 2020	$ 525,013
Increase from current period acquisition	1,440
Measurement period adjustments from prior period acquisitions	23
Decrease from disposition of businesses	(674)
Foreign currency translation	(1,541)
Balance at September 30, 2020	524,261
Environmental Services
Goodwill [Roll Forward]
Balance at January 1, 2020	212,531
Increase from current period acquisition	0
Measurement period adjustments from prior period acquisitions	23
Decrease from disposition of businesses	(674)
Foreign currency translation	(741)
Balance at September 30, 2020	211,139
Safety-Kleen
Goodwill [Roll Forward]
Balance at January 1, 2020	312,482
Increase from current period acquisition	1,440
Measurement period adjustments from prior period acquisitions	0
Decrease from disposition of businesses	0
Foreign currency translation	(800)
Balance at September 30, 2020	$ 313,122

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount of foreign currency translation gain (loss) which increases (decreases) an asset representing future economic benefits from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount of divestiture of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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