REVENUE RECOGNITION - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Midstream services revenue - affiliate	$ 40,767	$ 33,847
Gas gathering and compression
Disaggregation of Revenue [Line Items]
Midstream services revenue - affiliate	5,720	3,613
Gas processing
Disaggregation of Revenue [Line Items]
Midstream services revenue - affiliate	29,896	25,286
Transmission
Disaggregation of Revenue [Line Items]
Midstream services revenue - affiliate	4,175	4,853
NGL transmission
Disaggregation of Revenue [Line Items]
Midstream services revenue - affiliate	826	95
Other
Disaggregation of Revenue [Line Items]
Midstream services revenue - affiliate	$ 150	$ 0

Amount, including tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value-added and excise.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130545-203045

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130543-203045

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration