GOODWILL AND INTANGIBLE ASSETS - Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Intangible Assets
Amortizing intangible assets, Cost	$ 214,639		$ 214,373
Accumulated amortization	(34,512)		(31,788)
Amortizing intangible assets, Net	180,127		182,585
Total intangible assets, cost	266,417		266,144
Total intangible assets, net	231,905		234,356
Amortization of intangibles	2,670	$ 2,610
Permits and licenses
Intangible Assets
Nonamortizing intangible assets	51,650		51,645
Tradename
Intangible Assets
Nonamortizing intangible assets	128		126
Permits, licenses and lease
Intangible Assets
Amortizing intangible assets, Cost	110,517		110,341
Accumulated amortization	(10,170)		(9,462)
Amortizing intangible assets, Net	100,347		100,879
Customer relationships
Intangible Assets
Amortizing intangible assets, Cost	84,740		84,711
Accumulated amortization	(15,920)		(14,519)
Amortizing intangible assets, Net	68,820		70,192
Technology - formulae and processes
Intangible Assets
Amortizing intangible assets, Cost	6,827		6,770
Accumulated amortization	(1,371)		(1,305)
Amortizing intangible assets, Net	5,456		5,465
Customer backlog
Intangible Assets
Amortizing intangible assets, Cost	3,652		3,652
Accumulated amortization	(1,017)		(926)
Amortizing intangible assets, Net	2,635		2,726
Tradename
Intangible Assets
Amortizing intangible assets, Cost	4,318		4,318
Accumulated amortization	(4,009)		(3,650)
Amortizing intangible assets, Net	309		668
Developed software
Intangible Assets
Amortizing intangible assets, Cost	2,910		2,907
Accumulated amortization	(1,073)		(994)
Amortizing intangible assets, Net	1,837		1,913
Non-compete agreements
Intangible Assets
Amortizing intangible assets, Cost	747		747
Accumulated amortization	(746)		(742)
Amortizing intangible assets, Net	1		5
Internet domain and website
Intangible Assets
Amortizing intangible assets, Cost	540		540
Accumulated amortization	(79)		(72)
Amortizing intangible assets, Net	461		468
Database
Intangible Assets
Amortizing intangible assets, Cost	388		387
Accumulated amortization	(127)		(118)
Amortizing intangible assets, Net	$ 261		$ 269

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6388964&loc=d3e16225-109274

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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