BUSINESS COMBINATIONS - NRCG Merger (Details) $ in Thousands, $ in Millions			3 Months Ended		6 Months Ended		12 Months Ended
	Aug. 01, 2019 USD ($)	Aug. 01, 2019 CAD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	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			$ 469,278		469,278		$ 766,980
Additional information
Revenue since acquisition included in consolidated statements of operations			70,400		157,000
Operating loss since acquisition included in consolidated statements of operations			12,300		316,300
Acquisition-related costs included in selling, general and administrative expenses			2,973	$ 2,530	5,880	$ 2,671
Field and Industrial Services
Consideration paid and the fair value of assets acquired and liabilities assumed
Goodwill			300,023		300,023		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		131,653
Property and equipment			197,045		197,045		197,045
Identifiable intangible assets			303,600		303,600		303,600
Other assets			41,687		41,687		41,687
Current liabilities			(87,496)		(87,496)		(83,460)
Other liabilities			(57,581)		(57,581)		(57,581)
Total identifiable net assets			472,983		472,983		476,348
Goodwill			551,850		551,850		548,485	$ 551,900
Total purchase price					1,024,833		$ 1,024,833
Adjustments
Current liabilities - adjustments					4,036
Deferred income tax liabilities - adjustments					(671)
Total identifiable net assets - adjustment					(3,365)
Goodwill - adjustment					3,365
Additional information
Acquisition-related costs included in selling, general and administrative expenses			$ 2,900		5,800
Pro forma combined:
Revenue				276,862		508,057
Net income				$ 6,163		$ 3,306
NRC | Field and Industrial Services
Consideration paid and the fair value of assets acquired and liabilities assumed
Goodwill								$ 241,100
Adjustments
Goodwill - adjustment					$ 1,470
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