EQUITY METHOD INTERESTS - Summarized Financial Information of Equity Method Investments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Schedule of Equity Method Investments [Line Items]
Revenues		$ 10,378
Operating expenses		5,159
Operating income (loss)		5,219
Net income (loss)		5,219
Gulf Coast Express Pipeline LLC
Schedule of Equity Method Investments [Line Items]
Revenues	$ 92,205	1,643
Operating expenses	26,499	(395)
Operating income (loss)	65,706	2,038
Net income (loss)	65,658	2,707
Other comprehensive loss	0	0
EPIC Crude Holdings, LP
Schedule of Equity Method Investments [Line Items]
Revenues	40,759	0
Operating expenses	46,430	3,181
Operating income (loss)	(5,671)	(3,181)
Net income (loss)	(10,944)	(7,601)
Other comprehensive loss	(7,887)	0
Permian Highway Pipeline LLC
Schedule of Equity Method Investments [Line Items]
Revenues	0	0
Operating expenses	23	10
Operating income (loss)	(23)	(10)
Net income (loss)	425	(10)
Other comprehensive loss	0	$ 0
Breviloba, LLC
Schedule of Equity Method Investments [Line Items]
Revenues	42,818
Operating expenses	17,229
Operating income (loss)	25,589
Net income (loss)	22,184
Other comprehensive loss	$ 0