SEGMENT REPORTING (Assets by Reportable Segment) (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Property, plant and equipment, net	$ 1,596,872	$ 1,532,467
Goodwill	460,642	453,105
Permits and other intangible, net	502,532	506,818
Total assets	3,641,675	3,431,428
Technical Services
Segment Reporting Information [Line Items]
Property, plant and equipment, net	499,464	483,425
Goodwill	48,694	49,267
Permits and other intangible, net	73,632	73,601
Total assets	818,098	800,060
Industrial and Field Services
Segment Reporting Information [Line Items]
Property, plant and equipment, net	234,088	237,660
Goodwill	106,637	105,286
Permits and other intangible, net	14,215	14,649
Total assets	378,639	368,858
Kleen Performance Products
Segment Reporting Information [Line Items]
Property, plant and equipment, net	202,445	193,855
Goodwill	50,143	49,755
Permits and other intangible, net	139,725	140,410
Total assets	501,019	492,483
SK Environmental Services
Segment Reporting Information [Line Items]
Property, plant and equipment, net	306,462	264,539
Goodwill	220,854	216,589
Permits and other intangible, net	254,230	256,251
Total assets	858,544	805,488
Lodging Services
Segment Reporting Information [Line Items]
Property, plant and equipment, net	108,489	105,208
Goodwill	34,314	32,208
Permits and other intangible, net	7,004	7,045
Total assets	188,547	181,357
Oil and Gas Field Services
Segment Reporting Information [Line Items]
Property, plant and equipment, net	153,869	156,286
Goodwill	0	0
Permits and other intangible, net	13,726	14,862
Total assets	243,543	244,210
Corporate Items
Segment Reporting Information [Line Items]
Property, plant and equipment, net	92,055	91,494
Goodwill	0	0
Permits and other intangible, net	0	0
Total assets	$ 653,285	$ 538,972