SEGMENT REPORTING (Third Party Revenues to Direct Revenues) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Segment Reporting Information [Line Items]
Total revenues	$ 752,788	$ 697,510	$ 1,441,729	$ 1,333,593
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	752,788	697,510	1,441,729	1,333,593
Technical Services
Segment Reporting Information [Line Items]
Total revenues	254,487	229,130	484,705	448,235
Technical Services | Intersegment revenues, net
Segment Reporting Information [Line Items]
Total revenues	40,001	35,578	80,045	70,422
Technical Services | Corporate Items, net
Segment Reporting Information [Line Items]
Total revenues	408	667	1,130	1,055
Technical Services | Direct revenues
Segment Reporting Information [Line Items]
Total revenues	294,896	265,375	565,880	519,712
Industrial and Field Services
Segment Reporting Information [Line Items]
Total revenues	167,899	164,641	301,456	294,828
Industrial and Field Services | Intersegment revenues, net
Segment Reporting Information [Line Items]
Total revenues	(9,067)	(7,922)	(17,426)	(14,597)
Industrial and Field Services | Corporate Items, net
Segment Reporting Information [Line Items]
Total revenues	(133)	(303)	(29)	(316)
Industrial and Field Services | Direct revenues
Segment Reporting Information [Line Items]
Total revenues	158,699	156,416	284,001	279,915
Safety-Kleen
Segment Reporting Information [Line Items]
Total revenues	302,956	277,715	595,857	524,676
Safety-Kleen | Intersegment revenues, net
Segment Reporting Information [Line Items]
Total revenues	(31,639)	(29,092)	(63,708)	(57,613)
Safety-Kleen | Corporate Items, net
Segment Reporting Information [Line Items]
Total revenues	(2)	1	1	367
Safety-Kleen | Direct revenues
Segment Reporting Information [Line Items]
Total revenues	271,315	248,624	532,150	467,430
Oil, Gas and Lodging Services
Segment Reporting Information [Line Items]
Total revenues	27,245	24,860	59,377	63,911
Oil, Gas and Lodging Services | Intersegment revenues, net
Segment Reporting Information [Line Items]
Total revenues	705	1,436	1,089	1,788
Oil, Gas and Lodging Services | Corporate Items, net
Segment Reporting Information [Line Items]
Total revenues	45	79	139	183
Oil, Gas and Lodging Services | Direct revenues
Segment Reporting Information [Line Items]
Total revenues	27,995	26,375	60,605	65,882
Corporate Items
Segment Reporting Information [Line Items]
Total revenues	201	1,164	334	1,943
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	(318)	(444)	(1,241)	(1,289)
Corporate Items | Direct revenues
Segment Reporting Information [Line Items]
Total revenues	$ (117)	$ 720	$ (907)	$ 654