GOODWILL AND INTANGIBLE ASSETS - Goodwill (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Jan. 28, 2020	Dec. 31, 2019	Nov. 01, 2019	Aug. 01, 2019
Changes in goodwill
Balance at the beginning of the period	$ 766,980,000
Foreign currency translation	(1,970,000)
Balance at the end of the period	466,031,000
Accumulated Impairment
Impairment charges	(300,300,000)
NRC
Changes in goodwill
Balance at the beginning of the period	548,485,000
Purchase price allocation adjustment	1,021,000
Balance at the end of the period	549,506,000
Identifiable intangible assets	303,600,000		$ 303,600,000
Total identified intangible assets				$ 246,200,000
Impact Environmental Services Inc
Changes in goodwill
Acquisition	300,000
Balance at the end of the period	300,000
US Ecology Sarnia
Changes in goodwill
Identifiable intangible assets					$ 6,200,000
Environmental Services
Changes in goodwill
Balance at the beginning of the period	475,271,000
Foreign currency translation	(1,368,000)
Balance at the end of the period	474,478,000
Accumulated Impairment
Accumulated impairment at the beginning	(6,870,000)
Impairment charges	(283,600,000)
Accumulated impairment at the ending	(290,470,000)
Environmental Services | NRC
Changes in goodwill
Purchase price allocation adjustment	575,000
Field and Industrial Services
Changes in goodwill
Balance at the beginning of the period	298,579,000
Foreign currency translation	(602,000)
Balance at the end of the period	298,723,000
Accumulated Impairment
Impairment charges	(16,700,000)
Accumulated impairment at the ending	(16,700,000)
Field and Industrial Services | NRC
Changes in goodwill
Purchase price allocation adjustment	$ 446,000
Field and Industrial Services | Impact Environmental Services Inc
Changes in goodwill
Identifiable intangible assets		$ 900,000