SEGMENT INFORMATION - Adjusted EBITDA by Reportable Segment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting Information [Line Items]
Adjusted EBITDA	$ 78,806	$ 82,740	$ 233,397	$ 246,169
Utica Shale
Segment Reporting Information [Line Items]
Adjusted EBITDA	7,864	6,521	20,697	24,459
Ohio Gathering
Segment Reporting Information [Line Items]
Adjusted EBITDA	10,435	10,171	29,584	29,583
Williston Basin
Segment Reporting Information [Line Items]
Adjusted EBITDA	13,840	19,849	49,224	54,849
DJ Basin
Segment Reporting Information [Line Items]
Adjusted EBITDA	6,554	2,248	12,043	4,528
Permian Basin
Segment Reporting Information [Line Items]
Adjusted EBITDA	210		(996)
Piceance Basin
Segment Reporting Information [Line Items]
Adjusted EBITDA	24,044	27,583	74,627	82,211
Barnett Shale
Segment Reporting Information [Line Items]
Adjusted EBITDA	10,901	10,818	33,483	31,770
Marcellus Shale
Segment Reporting Information [Line Items]
Adjusted EBITDA	$ 4,958	$ 5,550	$ 14,735	$ 18,769