SEGMENT INFORMATION - Assets, Revenues, Depreciation and Amortization, and Capital Expenditures 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	Dec. 31, 2018
Segment Reporting Information [Line Items]
Assets	$ 2,901,456		$ 2,901,456		$ 3,020,562
Revenues	100,187	$ 127,479	331,281	$ 372,982
Depreciation and amortization	27,640	26,592	82,919	79,752
Capital expenditures			151,663	137,033
Reportable Segments
Segment Reporting Information [Line Items]
Assets	2,852,673		2,852,673		2,980,700
Revenues	99,653	107,619	304,303	322,701
Depreciation and amortization	26,917	26,104	81,083	78,288
Capital expenditures			135,541	135,662
Reportable Segments | Utica Shale
Segment Reporting Information [Line Items]
Assets	207,850		207,850		207,357
Revenues	8,865	7,974	23,951	28,437
Depreciation and amortization	1,913	1,887	5,744	5,773
Capital expenditures			2,473	3,922
Reportable Segments | Ohio Gathering
Segment Reporting Information [Line Items]
Assets	620,496		620,496		649,250
Reportable Segments | Williston Basin
Segment Reporting Information [Line Items]
Assets	445,838		445,838		526,819
Revenues	21,118	29,010	77,440	90,850
Depreciation and amortization	4,788	5,672	14,958	16,903
Capital expenditures			20,288	18,463
Reportable Segments | DJ Basin
Segment Reporting Information [Line Items]
Assets	187,542		187,542		166,580
Revenues	7,867	3,782	17,839	10,355
Depreciation and amortization	775	783	2,038	2,349
Capital expenditures			66,775	38,864
Reportable Segments | Barnett Shale
Segment Reporting Information [Line Items]
Assets	354,173		354,173		376,564
Revenues	17,820	21,020	52,452	53,345
Depreciation and amortization	4,045	3,760	12,542	11,276
Capital expenditures			317	914
Reportable Segments | Permian Basin
Segment Reporting Information [Line Items]
Assets	184,386		184,386		145,702
Revenues	4,885		12,545
Depreciation and amortization	1,312		3,547
Capital expenditures			43,422	67,640
Reportable Segments | Marcellus Shale
Segment Reporting Information [Line Items]
Assets	186,899		186,899		208,790
Revenues	5,987	7,150	18,081	23,025
Depreciation and amortization	2,286	2,273	6,855	6,819
Capital expenditures			347	557
Reportable Segments | Piceance Basin
Segment Reporting Information [Line Items]
Assets	665,489		665,489		699,638
Revenues	33,111	38,683	101,995	116,689
Depreciation and amortization	11,798	11,729	35,399	35,168
Capital expenditures			1,919	5,302
Corporate and Other
Segment Reporting Information [Line Items]
Assets	48,783		48,783		44,181
Revenues	534	23,636	31,196	57,234
Depreciation and amortization	$ 723	488	1,836	1,464
Capital expenditures			16,122	1,371
Eliminations
Segment Reporting Information [Line Items]
Assets					$ (4,319)
Revenues		$ (3,776)	$ (4,218)	$ (6,953)