SEGMENT INFORMATION - Reconciliation of Net Income to Adjusted EBITDA (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting [Abstract]
Income (loss) before income taxes and income (loss) from equity method investees	$ 88,614,000	$ (7,768,000)	$ (216,268,000)
Add:
Corporate and other	39,140,000	37,589,000	27,352,000
Interest expense	68,131,000	63,810,000	59,092,000
Early extinguishment of debt	22,039,000	0	0
Deferred Purchase Price Obligation	(200,322,000)	55,854,000	0
Depreciation and amortization	114,872,000	112,661,000	105,903,000
Proportional adjusted EBITDA for equity method investees	41,246,000	45,602,000	33,667,000
Adjustments related to MVC shortfall payments	(41,373,000)	11,600,000	(11,902,000)
Unit-based and noncash compensation	7,951,000	7,985,000	7,017,000
Loss (gain) on asset sales, net	527,000	93,000	(172,000)
Long-lived asset impairment	188,702,000	1,764,000	9,305,000
Goodwill impairment	0	0	248,851,000
Less:
Interest income	0	0	2,000
Total of reportable segments' measures of profit or loss	$ 329,527,000	$ 329,190,000	$ 262,843,000