GOODWILL AND OTHER INTANGIBLE ASSETS - Rollforward of Goodwill (Details) $ in Thousands	6 Months Ended
Jun. 30, 2020 USD ($)
Goodwill [Roll Forward]
Balance at January 1, 2020	$ 525,013
Increase from current period acquisition	1,487
Measurement period adjustments from prior period acquisitions	23
Decrease from disposition of businesses	(674)
Foreign currency translation	(2,695)
Balance at June 30, 2020	523,154
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	(1,263)
Balance at June 30, 2020	210,617
Safety-Kleen
Goodwill [Roll Forward]
Balance at January 1, 2020	312,482
Increase from current period acquisition	1,487
Measurement period adjustments from prior period acquisitions	0
Decrease from disposition of businesses	0
Foreign currency translation	(1,432)
Balance at June 30, 2020	$ 312,537

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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