SEGMENT REPORTING (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014 segment	Mar. 31, 2013
Segment reporting information
Number of reportable segments	5
Number of operations for which the revenues are insignificant	2
Total revenues	$ 846,667	$ 862,163
Adjusted EBITDA, Total	101,986	111,228
Reconciliation to Consolidated Statements of Income:
Pre-tax, non-cash acquisition accounting inventory adjustment	0	13,559
Accretion of environmental liabilities	2,724	2,835
Depreciation and amortization	69,356	60,006
Income from operations	29,906	34,828
Other income	(4,178)	(525)
Interest expense, net of interest income	19,554	19,873
Income before provision for income taxes	14,530	15,480
Technical Services
Segment reporting information
Total revenues	274,614	259,210
Adjusted EBITDA, Total	62,177	60,045
Oil Re-refining and Recycling
Segment reporting information
Total revenues	81,773	90,370
Adjusted EBITDA, Total	13,432	15,312
SK Environmental Services
Segment reporting information
Total revenues	180,318	194,444
Adjusted EBITDA, Total	21,976	27,040
Industrial and Field Services
Segment reporting information
Total revenues	204,719	208,200
Adjusted EBITDA, Total	34,141	36,346
Oil and Gas Field Services
Segment reporting information
Total revenues	105,601	120,638
Adjusted EBITDA, Total	16,299	27,551
Corporate Items
Segment reporting information
Total revenues	(358)	(10,699)
Adjusted EBITDA, Total	(46,039)	(55,066)
Third party revenues
Segment reporting information
Total revenues	846,667	862,163
Third party revenues | Technical Services
Segment reporting information
Total revenues	236,781	233,939
Third party revenues | Oil Re-refining and Recycling
Segment reporting information
Total revenues	137,986	146,931
Third party revenues | SK Environmental Services
Segment reporting information
Total revenues	152,322	152,955
Third party revenues | Industrial and Field Services
Segment reporting information
Total revenues	215,676	221,418
Third party revenues | Oil and Gas Field Services
Segment reporting information
Total revenues	103,751	116,696
Third party revenues | Corporate Items
Segment reporting information
Total revenues	151	(9,776)
Intersegment revenues, net
Segment reporting information
Total revenues
Intersegment revenues, net | Technical Services
Segment reporting information
Total revenues	37,434	24,419
Intersegment revenues, net | Oil Re-refining and Recycling
Segment reporting information
Total revenues	(56,213)	(56,561)
Intersegment revenues, net | SK Environmental Services
Segment reporting information
Total revenues	28,054	41,405
Intersegment revenues, net | Industrial and Field Services
Segment reporting information
Total revenues	(11,113)	(13,356)
Intersegment revenues, net | Oil and Gas Field Services
Segment reporting information
Total revenues	1,838	4,093
Intersegment revenues, net | Corporate Items
Segment reporting information
Total revenues	0	0
Corporate Items, net
Segment reporting information
Total revenues	0	0
Corporate Items, net | Technical Services
Segment reporting information
Total revenues	399	852
Corporate Items, net | Oil Re-refining and Recycling
Segment reporting information
Total revenues	0	0
Corporate Items, net | SK Environmental Services
Segment reporting information
Total revenues	(58)	84
Corporate Items, net | Industrial and Field Services
Segment reporting information
Total revenues	156	138
Corporate Items, net | Oil and Gas Field Services
Segment reporting information
Total revenues	12	(151)
Corporate Items, net | Corporate Items
Segment reporting information
Total revenues	$ (509)	$ (923)