SEGMENT REPORTING (Third Party Revenues to Direct Revenues) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information [Line Items]
Total revenues	$ 849,140	$ 752,788	$ 1,598,918	$ 1,441,729
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	849,140	752,788	1,598,918	1,441,729
Environmental Services
Segment Reporting Information [Line Items]
Total revenues	519,916	449,631	959,604	845,538
Environmental Services | Intersegment revenues, net
Segment Reporting Information [Line Items]
Total revenues	34,291	31,639	66,256	63,708
Environmental Services | Corporate Items, net
Segment Reporting Information [Line Items]
Total revenues	607	320	1,401	1,240
Environmental Services | Direct revenues
Segment Reporting Information [Line Items]
Total revenues	554,814	481,590	1,027,261	910,486
Safety-Kleen
Segment Reporting Information [Line Items]
Total revenues	328,715	302,956	638,633	595,857
Safety-Kleen | Intersegment revenues, net
Segment Reporting Information [Line Items]
Total revenues	(34,291)	(31,639)	(66,256)	(63,708)
Safety-Kleen | Corporate Items, net
Segment Reporting Information [Line Items]
Total revenues	11	(2)	22	1
Safety-Kleen | Direct revenues
Segment Reporting Information [Line Items]
Total revenues	294,435	271,315	572,399	532,150
Corporate Items
Segment Reporting Information [Line Items]
Total revenues	509	201	681	334
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	(618)	(318)	(1,423)	(1,241)
Corporate Items | Direct revenues
Segment Reporting Information [Line Items]
Total revenues	$ (109)	$ (117)	$ (742)	$ (907)