GOODWILL AND INTANGIBLE ASSETS - Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Intangible Assets
Amortizing intangible assets, Cost	$ 216,839		$ 216,839		$ 214,373
Accumulated amortization	(39,930)		(39,930)		(31,788)
Amortizing intangible assets, Net	176,909		176,909		182,585
Total intangible assets, cost	268,666		268,666		266,144
Total intangible assets, net	228,736		228,736		234,356
Amortization of intangibles	2,300	$ 2,651	7,586	$ 7,907
Permits and licenses
Intangible Assets
Nonamortizing intangible assets	51,691		51,691		51,645
Tradename
Intangible Assets
Nonamortizing intangible assets	136		136		126
Permits, licenses and lease
Intangible Assets
Amortizing intangible assets, Cost	111,961		111,961		110,341
Accumulated amortization	(11,814)		(11,814)		(9,462)
Amortizing intangible assets, Net	100,147		100,147		100,879
Customer relationships
Intangible Assets
Amortizing intangible assets, Cost	85,003		85,003		84,711
Accumulated amortization	(18,781)		(18,781)		(14,519)
Amortizing intangible assets, Net	66,222		66,222		70,192
Technology - Formulae and processes
Intangible Assets
Amortizing intangible assets, Cost	7,296		7,296		6,770
Accumulated amortization	(1,582)		(1,582)		(1,305)
Amortizing intangible assets, Net	5,714		5,714		5,465
Customer backlog
Intangible Assets
Amortizing intangible assets, Cost	3,652		3,652		3,652
Accumulated amortization	(1,200)		(1,200)		(926)
Amortizing intangible assets, Net	2,452		2,452		2,726
Tradename
Intangible Assets
Amortizing intangible assets, Cost	4,318		4,318		4,318
Accumulated amortization	(4,318)		(4,318)		(3,650)
Amortizing intangible assets, Net					668
Developed software
Intangible Assets
Amortizing intangible assets, Cost	2,928		2,928		2,907
Accumulated amortization	(1,246)		(1,246)		(994)
Amortizing intangible assets, Net	1,682		1,682		1,913
Non-compete agreements
Intangible Assets
Amortizing intangible assets, Cost	748		748		747
Accumulated amortization	(748)		(748)		(742)
Amortizing intangible assets, Net					5
Internet domain and website
Intangible Assets
Amortizing intangible assets, Cost	540		540		540
Accumulated amortization	(93)		(93)		(72)
Amortizing intangible assets, Net	447		447		468
Database
Intangible Assets
Amortizing intangible assets, Cost	393		393		387
Accumulated amortization	(148)		(148)		(118)
Amortizing intangible assets, Net	$ 245		$ 245		$ 269