GOODWILL - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Goodwill [Line Items]
Goodwill impairment	$ 16,211	$ 0	$ 16,211
Mountaineer Midstream
Goodwill [Line Items]
Goodwill impairment	$ 16,200		$ 16,200

Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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