SEGMENT REPORTING (Third Party Revenues to Direct Revenues) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Total revenues	$ 843,181	$ 755,846	$ 2,442,099	$ 2,197,575
Intersegment revenues, net
Segment Reporting Information [Line Items]
Total revenues	0	0	0	0
Corporate Items, net
Segment Reporting Information [Line Items]
Total revenues	0	0	0	0
Direct revenues
Segment Reporting Information [Line Items]
Total revenues	843,181	755,846	2,442,099	2,197,575
Environmental Services
Segment Reporting Information [Line Items]
Total revenues	508,813	440,163	1,468,417	1,285,701
Environmental Services | Intersegment revenues, net
Segment Reporting Information [Line Items]
Total revenues	33,022	31,757	99,278	95,465
Environmental Services | Corporate Items, net
Segment Reporting Information [Line Items]
Total revenues	1,145	761	2,546	2,001
Environmental Services | Direct revenues
Segment Reporting Information [Line Items]
Total revenues	542,980	472,681	1,570,241	1,383,167
Safety-Kleen
Segment Reporting Information [Line Items]
Total revenues	333,901	315,028	972,534	910,885
Safety-Kleen | Intersegment revenues, net
Segment Reporting Information [Line Items]
Total revenues	(33,022)	(31,757)	(99,278)	(95,465)
Safety-Kleen | Corporate Items, net
Segment Reporting Information [Line Items]
Total revenues	6	3	28	4
Safety-Kleen | Direct revenues
Segment Reporting Information [Line Items]
Total revenues	300,885	283,274	873,284	815,424
Corporate Items
Segment Reporting Information [Line Items]
Total revenues	467	655	1,148	989
Corporate Items | Intersegment revenues, net
Segment Reporting Information [Line Items]
Total revenues	0	0	0	0
Corporate Items | Corporate Items, net
Segment Reporting Information [Line Items]
Total revenues	(1,151)	(764)	(2,574)	(2,005)
Corporate Items | Direct revenues
Segment Reporting Information [Line Items]
Total revenues	$ (684)	$ (109)	$ (1,426)	$ (1,016)