GOODWILL AND INTANGIBLE ASSETS - Intangible Assets (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Jan. 28, 2020	Dec. 31, 2019	Aug. 01, 2019
Intangible Assets
Amortizing intangible assets, Cost	$ 535,581,000			$ 537,709,000
Accumulated amortization	(75,346,000)			(66,753,000)
Amortizing intangible assets, Net	460,235,000			470,956,000
Total intangible assets, cost	639,470,000			641,655,000
Total intangible assets, net	564,124,000			574,902,000
Amortization of intangible assets	9,441,000	$ 2,811,000
Goodwill	466,031,000			766,980,000
Permits and licenses
Intangible Assets
Non-amortizing intangible assets	103,769,000			103,816,000
Tradename
Intangible Assets
Non-amortizing intangible assets	120,000			130,000
Permits, licenses and lease
Intangible Assets
Amortizing intangible assets, Cost	172,668,000			174,339,000
Accumulated amortization	(19,239,000)			(18,707,000)
Amortizing intangible assets, Net	153,429,000			155,632,000
Customer relationships
Intangible Assets
Amortizing intangible assets, Cost	333,152,000			333,090,000
Accumulated amortization	(41,781,000)			(35,254,000)
Amortizing intangible assets, Net	291,371,000			297,836,000
Technology - formulae and processes
Intangible Assets
Amortizing intangible assets, Cost	6,421,000			6,964,000
Accumulated amortization	(1,907,000)			(2,013,000)
Amortizing intangible assets, Net	4,514,000			4,951,000
Customer backlog
Intangible Assets
Amortizing intangible assets, Cost	3,652,000			3,652,000
Accumulated amortization	(2,113,000)			(2,022,000)
Amortizing intangible assets, Net	1,539,000			1,630,000
Tradename
Intangible Assets
Amortizing intangible assets, Cost	10,390,000			10,390,000
Accumulated amortization	(5,644,000)			(4,832,000)
Amortizing intangible assets, Net	4,746,000			5,558,000
Developed software
Intangible Assets
Amortizing intangible assets, Cost	2,874,000			2,895,000
Accumulated amortization	(1,936,000)			(1,884,000)
Amortizing intangible assets, Net	938,000			1,011,000
Non-compete agreements
Intangible Assets
Amortizing intangible assets, Cost	5,506,000			5,455,000
Accumulated amortization	(2,372,000)			(1,694,000)
Amortizing intangible assets, Net	3,134,000			3,761,000
Internet domain and website
Intangible Assets
Amortizing intangible assets, Cost	536,000			536,000
Accumulated amortization	(163,000)			(156,000)
Amortizing intangible assets, Net	373,000			380,000
Database
Intangible Assets
Amortizing intangible assets, Cost	382,000			388,000
Accumulated amortization	(191,000)			(191,000)
Amortizing intangible assets, Net	191,000			197,000
Impact Environmental Services Inc
Intangible Assets
Amortizing intangible assets, Cost	900,000
Goodwill	300,000
US Ecology Sarnia
Intangible Assets
Goodwill					$ 7,700,000
Environmental Services
Intangible Assets
Goodwill	474,478,000			475,271,000
Field and Industrial Services
Intangible Assets
Goodwill	$ 298,723,000			$ 298,579,000
Field and Industrial Services | Impact Environmental Services Inc
Intangible Assets
Goodwill			$ 300,000