GOODWILL AND INTANGIBLE ASSETS, NET - Intangible Assets, Net (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Intangible Assets, Net
Gross carrying amount	$ 333,787	$ 333,787
Accumulated amortization	(213,722)	(178,355)
Net book value	120,065	155,432
Impairment of intangible assets	0	0	$ 11,900
Amortization expense for definite lived intangible assets	35,367	47,576	$ 41,135
2018	26,200
2019	21,800
2020	18,200
2021	11,500
2022	7,300
Trademarks and trade names
Intangible Assets, Net
Gross carrying amount	15,354	15,354
Accumulated amortization	(8,881)	(7,724)
Net book value	$ 6,473	7,630
Trademarks and trade names | Weighted average
Intangible Assets, Net
Estimated useful lives	13 years
Customer related intangible assets
Intangible Assets, Net
Gross carrying amount	$ 277,828	277,828
Accumulated amortization	(188,258)	(156,980)
Net book value	$ 89,570	120,848
Customer related intangible assets | Weighted average
Intangible Assets, Net
Estimated useful lives	10 years
Operating agreement
Intangible Assets, Net
Gross carrying amount	$ 35,000	35,000
Accumulated amortization	(13,865)	(12,104)
Net book value	$ 21,135	22,896
Operating agreement | Weighted average
Intangible Assets, Net
Estimated useful lives	20 years
Non-compete agreements
Intangible Assets, Net
Gross carrying amount	$ 1,560	1,560
Accumulated amortization	(897)	(507)
Net book value	$ 663	1,053
Non-compete agreements | Weighted average
Intangible Assets, Net
Estimated useful lives	4 years
Intellectual property
Intangible Assets, Net
Gross carrying amount	$ 300	300
Accumulated amortization	(115)	(85)
Net book value	$ 185	215
Intellectual property | Weighted average
Intangible Assets, Net
Estimated useful lives	10 years
Other intangible assets
Intangible Assets, Net
Gross carrying amount	$ 3,745	3,745
Accumulated amortization	(1,706)	(955)
Net book value	$ 2,039	$ 2,790
Other intangible assets | Weighted average
Intangible Assets, Net
Estimated useful lives	5 years