GOODWILL AND OTHER INTANGIBLE ASSETS (Rollforward of Goodwill) (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2016 USD ($)
Goodwill [Roll Forward]
Balance at beginning of year	$ 453,105
Acquired from acquisitions	1,197
Measurement period adjustment from prior acquisitions	2,095
Foreign currency translation and other	5,094
Balance at end of year	461,491
Technical Services
Goodwill [Roll Forward]
Balance at beginning of year	49,267
Balance at end of year	48,688
Industrial and Field Services
Goodwill [Roll Forward]
Balance at beginning of year	105,286
Balance at end of year	106,605
Kleen Performance Products
Goodwill [Roll Forward]
Balance at beginning of year	49,755
Balance at end of year	51,109
SK Environmental Services
Goodwill [Roll Forward]
Balance at beginning of year	216,589
Balance at end of year	220,824
Lodging Services
Goodwill [Roll Forward]
Balance at beginning of year	32,208
Balance at end of year	34,265
Oil and Gas Field Services
Goodwill [Roll Forward]
Balance at beginning of year	0
Balance at end of year	0
Operating Segments | Technical Services
Goodwill [Roll Forward]
Balance at beginning of year	49,267
Acquired from acquisitions	0
Measurement period adjustment from prior acquisitions	0
Foreign currency translation and other	(579)
Balance at end of year	48,688
Operating Segments | Industrial and Field Services
Goodwill [Roll Forward]
Balance at beginning of year	105,286
Acquired from acquisitions	0
Measurement period adjustment from prior acquisitions	0
Foreign currency translation and other	1,319
Balance at end of year	106,605
Operating Segments | Kleen Performance Products
Goodwill [Roll Forward]
Balance at beginning of year	49,755
Acquired from acquisitions	1,197
Measurement period adjustment from prior acquisitions	0
Foreign currency translation and other	157
Balance at end of year	51,109
Operating Segments | SK Environmental Services
Goodwill [Roll Forward]
Balance at beginning of year	216,589
Acquired from acquisitions	0
Measurement period adjustment from prior acquisitions	2,095
Foreign currency translation and other	2,140
Balance at end of year	220,824
Operating Segments | Lodging Services
Goodwill [Roll Forward]
Balance at beginning of year	32,208
Acquired from acquisitions	0
Measurement period adjustment from prior acquisitions	0
Foreign currency translation and other	2,057
Balance at end of year	34,265
Operating Segments | Oil and Gas Field Services
Goodwill [Roll Forward]
Balance at beginning of year	0
Acquired from acquisitions	0
Measurement period adjustment from prior acquisitions	0
Foreign currency translation and other	0
Balance at end of year	$ 0