SEGMENT INFORMATION - Adjusted EBITDA by Reportable Segment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Segment Reporting Information [Line Items]
Adjusted EBITDA	$ 78,775	$ 80,932
Utica Shale
Segment Reporting Information [Line Items]
Adjusted EBITDA	6,193	8,715
Ohio Gathering
Segment Reporting Information [Line Items]
Adjusted EBITDA	9,210	10,477
Williston Basin
Segment Reporting Information [Line Items]
Adjusted EBITDA	18,734	15,970
DJ Basin
Segment Reporting Information [Line Items]
Adjusted EBITDA	2,673	1,321
Barnett Shale
Segment Reporting Information [Line Items]
Adjusted EBITDA	11,374	9,859
Permian Basin
Segment Reporting Information [Line Items]
Adjusted EBITDA	(550)
Marcellus Shale
Segment Reporting Information [Line Items]
Adjusted EBITDA	5,142	6,676
Piceance Basin
Segment Reporting Information [Line Items]
Adjusted EBITDA	$ 25,999	$ 27,914