REVENUE - Schedule of Disaggregated Revenue by Geographic Area and Major Products and Services Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation Of Revenue [Line Items]
Total revenues	$ 128,183	$ 101,792	$ 245,503	$ 237,597
Utica Shale
Disaggregation Of Revenue [Line Items]
Total revenues	10,422		20,463
Williston Basin
Disaggregation Of Revenue [Line Items]
Total revenues	33,416		61,840
Piceance/DJ Basins
Disaggregation Of Revenue [Line Items]
Total revenues	42,992		84,579
Barnett Shale
Disaggregation Of Revenue [Line Items]
Total revenues	16,155		32,325
Marcellus Shale
Disaggregation Of Revenue [Line Items]
Total revenues	8,050		15,875
Total Reportable Segments
Disaggregation Of Revenue [Line Items]
Total revenues	111,035		215,082
All Other Segments
Disaggregation Of Revenue [Line Items]
Total revenues	17,148		30,421
Gathering Services and Related Fees
Disaggregation Of Revenue [Line Items]
Total revenues	89,585		173,946
Gathering Services and Related Fees | Utica Shale
Disaggregation Of Revenue [Line Items]
Total revenues	10,422		20,463
Gathering Services and Related Fees | Williston Basin
Disaggregation Of Revenue [Line Items]
Total revenues	23,106		40,772
Gathering Services and Related Fees | Piceance/DJ Basins
Disaggregation Of Revenue [Line Items]
Total revenues	36,170		71,464
Gathering Services and Related Fees | Barnett Shale
Disaggregation Of Revenue [Line Items]
Total revenues	14,080		27,717
Gathering Services and Related Fees | Marcellus Shale
Disaggregation Of Revenue [Line Items]
Total revenues	8,050		15,875
Gathering Services and Related Fees | Total Reportable Segments
Disaggregation Of Revenue [Line Items]
Total revenues	91,828		176,291
Gathering Services and Related Fees | All Other Segments
Disaggregation Of Revenue [Line Items]
Total revenues	(2,243)		(2,345)
Natural Gas, NGLs and Condensate Sales
Disaggregation Of Revenue [Line Items]
Total revenues	31,891		58,008
Natural Gas, NGLs and Condensate Sales | Utica Shale
Disaggregation Of Revenue [Line Items]
Total revenues	0		0
Natural Gas, NGLs and Condensate Sales | Williston Basin
Disaggregation Of Revenue [Line Items]
Total revenues	7,350		15,196
Natural Gas, NGLs and Condensate Sales | Piceance/DJ Basins
Disaggregation Of Revenue [Line Items]
Total revenues	4,675		9,000
Natural Gas, NGLs and Condensate Sales | Barnett Shale
Disaggregation Of Revenue [Line Items]
Total revenues	381		926
Natural Gas, NGLs and Condensate Sales | Marcellus Shale
Disaggregation Of Revenue [Line Items]
Total revenues	0		0
Natural Gas, NGLs and Condensate Sales | Total Reportable Segments
Disaggregation Of Revenue [Line Items]
Total revenues	12,406		25,122
Natural Gas, NGLs and Condensate Sales | All Other Segments
Disaggregation Of Revenue [Line Items]
Total revenues	19,485		32,886
Other Revenues
Disaggregation Of Revenue [Line Items]
Total revenues	6,707		13,549
Other Revenues | Utica Shale
Disaggregation Of Revenue [Line Items]
Total revenues	0		0
Other Revenues | Williston Basin
Disaggregation Of Revenue [Line Items]
Total revenues	2,960		5,872
Other Revenues | Piceance/DJ Basins
Disaggregation Of Revenue [Line Items]
Total revenues	2,147		4,115
Other Revenues | Barnett Shale
Disaggregation Of Revenue [Line Items]
Total revenues	1,694		3,682
Other Revenues | Marcellus Shale
Disaggregation Of Revenue [Line Items]
Total revenues	0		0
Other Revenues | Total Reportable Segments
Disaggregation Of Revenue [Line Items]
Total revenues	6,801		13,669
Other Revenues | All Other Segments
Disaggregation Of Revenue [Line Items]
Total revenues	$ (94)		$ (120)