GOODWILL AND OTHER INTANGIBLE ASSETS (Changes to Goodwill) (Details) $ in Thousands	3 Months Ended
Mar. 31, 2021 USD ($)
Goodwill [Roll Forward]
Balance at January 1, 2021	$ 527,023
Increase from current period acquisition	15,875
Foreign currency translation	707
Balance at March 31, 2021	543,605
Environmental Services
Goodwill [Roll Forward]
Balance at January 1, 2021	401,918
Increase from current period acquisition	0
Foreign currency translation	520
Balance at March 31, 2021	402,438
Safety-Kleen Sustainability Solutions
Goodwill [Roll Forward]
Balance at January 1, 2021	125,105
Increase from current period acquisition	15,875
Foreign currency translation	187
Balance at March 31, 2021	$ 141,167

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.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
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Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

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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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