BUSINESS COMBINATIONS - Preliminary fair value estimates of assets acquired and liabilities assumed recognized (Details) $ in Thousands, $ in Millions					3 Months Ended	12 Months Ended
	Oct. 31, 2020 USD ($)	Jan. 28, 2020 USD ($)	Aug. 01, 2019 USD ($)	Aug. 01, 2019 CAD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Nov. 01, 2019 USD ($)
Consideration paid and the fair value of assets acquired and liabilities assumed
Goodwill					$ 413,037	$ 413,126	$ 413,037	$ 766,980
Depreciation and amortization of plant and equipment						70,799	66,561	41,423
Amortization of intangibles assets						34,614	37,344	15,491
Environmental Services
Consideration paid and the fair value of assets acquired and liabilities assumed
Goodwill					166,863	166,925	166,863	166,415
Field & Industrial Services
Consideration paid and the fair value of assets acquired and liabilities assumed
Goodwill					237,341	237,368	237,341	$ 298,579
Goodwill impairment charges					$ 14,400
NRC
Consideration paid and the fair value of assets acquired and liabilities assumed
Current assets	$ 130,110
Property and equipment	170,208
Identifiable intangible assets	309,500
Other assets	41,687
Current liabilities	(89,733)
Deferred income tax liabilities	(54,974)
Other liabilities	(59,363)
Total identifiable net assets	447,435
Goodwill	577,398					$ 577,400			$ 577,400
Total purchase price	$ 1,024,833
Goodwill expected to be deductible for income tax purposes									33,300
Goodwill impairment charges							383,800
Adjustments
Goodwill - adjustment							28,912
NRC | Environmental Services
Consideration paid and the fair value of assets acquired and liabilities assumed
Goodwill									399,500
NRC | Field & Industrial Services
Consideration paid and the fair value of assets acquired and liabilities assumed
Goodwill									$ 177,900
Goodwill impairment charges							19,900
Adjustments
Goodwill - adjustment							$ (61,735)
US Ecology Sarnia
Consideration paid and the fair value of assets acquired and liabilities assumed
Identifiable intangible assets			$ 6,200
Goodwill			7,700
Total purchase price			$ 17,900	$ 23.5
Impact Environmental Services Inc
Consideration paid and the fair value of assets acquired and liabilities assumed
Identifiable intangible assets		$ 900
Goodwill		300
Total purchase price		$ 3,300