BUSINESS COMBINATIONS - NRCG Merger (Details) $ in Thousands, $ in Millions			3 Months Ended		12 Months Ended
	Aug. 01, 2019 USD ($)	Aug. 01, 2019 CAD ($)	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)	Nov. 01, 2019 USD ($)
Acquisition
Payment to acquire business, net of cash acquired			$ 3,309
Consideration paid and the fair value of assets acquired and liabilities assumed
Goodwill			466,031		$ 766,980
Additional information
Revenue since acquisition included in consolidated statements of operations			86,600
Operating loss since acquisition included in consolidated statements of operations			304,000
Acquisition-related costs included in selling, general and administrative expenses			2,907	$ 141
Field and Industrial Services
Consideration paid and the fair value of assets acquired and liabilities assumed
Goodwill			298,723		298,579
NRC
Acquisition
Acquisition price			1,024,833		1,024,833
Consideration paid and the fair value of assets acquired and liabilities assumed
Current assets			131,653		131,653
Property and equipment			197,045		197,045
Identifiable intangible assets			303,600		303,600
Other assets			41,687		41,687
Current liabilities			(84,675)		(83,460)
Other liabilities			(57,581)		(57,581)
Total identifiable net assets			475,327		476,348
Goodwill			549,506		548,485	$ 549,500
Total purchase price			1,024,833		$ 1,024,833
Adjustments
Current liabilities - adjustments			1,215
Deferred income tax liabilities - adjustments			(194)
Total identifiable net assets - adjustment			(1,021)
Goodwill - adjustment			1,021
Pro forma combined:
Revenue				231,195
Net loss				$ (2,857)
NRC | Field and Industrial Services
Consideration paid and the fair value of assets acquired and liabilities assumed
Goodwill						$ 240,100
Adjustments
Goodwill - adjustment			$ 446
US Ecology Sarnia
Acquisition
Percentage of outstanding shares acquired	100.00%
Acquisition price	$ 17,900	$ 23.5
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
Additional information
Weighted average amortization period	14 years	14 years