GOODWILL AND INTANGIBLE ASSETS - Intangible Assets (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Jan. 28, 2020	Dec. 31, 2019	Aug. 01, 2019
Intangible Assets
Amortizing intangible assets, Cost	$ 536,970,000		$ 536,970,000			$ 537,709,000
Accumulated amortization	(84,912,000)		(84,912,000)			(66,753,000)
Amortizing intangible assets, Net	452,058,000		452,058,000			470,956,000
Total intangible assets, cost	640,885,000		640,885,000			641,655,000
Total intangible assets, net	555,973,000		555,973,000			574,902,000
Amortization of intangible assets	9,193,000	$ 2,863,000	18,634,000	$ 5,674,000
Goodwill	469,278,000		469,278,000			766,980,000
Permits and licenses
Intangible Assets
Non-amortizing intangible assets	103,790,000		103,790,000			103,816,000
Tradename
Intangible Assets
Non-amortizing intangible assets	125,000		125,000			130,000
Permits, licenses and lease
Intangible Assets
Amortizing intangible assets, Cost	173,435,000		173,435,000			174,339,000
Accumulated amortization	(20,492,000)		(20,492,000)			(18,707,000)
Amortizing intangible assets, Net	152,943,000		152,943,000			155,632,000
Customer relationships
Intangible Assets
Amortizing intangible assets, Cost	333,491,000		333,491,000			333,090,000
Accumulated amortization	(48,275,000)		(48,275,000)			(35,254,000)
Amortizing intangible assets, Net	285,216,000		285,216,000			297,836,000
Technology - formulae and processes
Intangible Assets
Amortizing intangible assets, Cost	6,670,000		6,670,000			6,964,000
Accumulated amortization	(2,035,000)		(2,035,000)			(2,013,000)
Amortizing intangible assets, Net	4,635,000		4,635,000			4,951,000
Customer backlog
Intangible Assets
Amortizing intangible assets, Cost	3,652,000		3,652,000			3,652,000
Accumulated amortization	(2,204,000)		(2,204,000)			(2,022,000)
Amortizing intangible assets, Net	1,448,000		1,448,000			1,630,000
Tradename
Intangible Assets
Amortizing intangible assets, Cost	10,390,000		10,390,000			10,390,000
Accumulated amortization	(6,457,000)		(6,457,000)			(4,832,000)
Amortizing intangible assets, Net	3,933,000		3,933,000			5,558,000
Developed software
Intangible Assets
Amortizing intangible assets, Cost	2,884,000		2,884,000			2,895,000
Accumulated amortization	(2,018,000)		(2,018,000)			(1,884,000)
Amortizing intangible assets, Net	866,000		866,000			1,011,000
Non-compete agreements
Intangible Assets
Amortizing intangible assets, Cost	5,528,000		5,528,000			5,455,000
Accumulated amortization	(3,063,000)		(3,063,000)			(1,694,000)
Amortizing intangible assets, Net	2,465,000		2,465,000			3,761,000
Internet domain and website
Intangible Assets
Amortizing intangible assets, Cost	536,000		536,000			536,000
Accumulated amortization	(170,000)		(170,000)			(156,000)
Amortizing intangible assets, Net	366,000		366,000			380,000
Database
Intangible Assets
Amortizing intangible assets, Cost	384,000		384,000			388,000
Accumulated amortization	(198,000)		(198,000)			(191,000)
Amortizing intangible assets, Net	186,000		186,000			197,000
Impact Environmental Services Inc
Intangible Assets
Amortizing intangible assets, Cost	900,000		900,000
Goodwill	300,000		300,000
US Ecology Sarnia
Intangible Assets
Goodwill							$ 7,700,000
Environmental Services
Intangible Assets
Goodwill	476,425,000		476,425,000			475,271,000
Field and Industrial Services
Intangible Assets
Goodwill	$ 300,023,000		$ 300,023,000			$ 298,579,000
Field and Industrial Services | Impact Environmental Services Inc
Intangible Assets
Goodwill					$ 300,000