EQUITY METHOD INTERESTS - Summarized Financial Information of Equity Method Investments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Schedule of Equity Method Investments [Line Items]
Revenues	$ 40,172	$ 34,009	$ 113,152	$ 91,994
Operating income (loss)	18,948	(6,583)	49,381	(7,294)
Net income (loss)	$ 29,322	$ (8,188)	20,192	(7,958)
Equity Method Investment, Nonconsolidated Investee or Group of Investees
Schedule of Equity Method Investments [Line Items]
Revenues				78,749
Operating expenses				27,189
Operating income (loss)				51,560
Net income (loss)				51,560
Equity Method Investment, Nonconsolidated Investee or Group of Investees | Gulf Coast Express Pipeline LLC
Schedule of Equity Method Investments [Line Items]
Revenues			273,760	16,476
Operating expenses			77,606	1,218
Operating income (loss)			196,154	15,258
Net income (loss)			195,460	17,090
Other comprehensive loss			0	0
Equity Method Investment, Nonconsolidated Investee or Group of Investees | EPIC Crude Holdings, LP
Schedule of Equity Method Investments [Line Items]
Revenues			128,837	8,015
Operating expenses			138,945	33,610
Operating income (loss)			(10,108)	(25,595)
Net income (loss)			(53,048)	(35,620)
Other comprehensive loss			(752)	(11,450)
Equity Method Investment, Nonconsolidated Investee or Group of Investees | Permian Highway Pipeline LLC
Schedule of Equity Method Investments [Line Items]
Revenues			0	0
Operating expenses			69	41
Operating income (loss)			(69)	(41)
Net income (loss)			587	785
Other comprehensive loss			0	$ 0
Equity Method Investment, Nonconsolidated Investee or Group of Investees | Breviloba, LLC
Schedule of Equity Method Investments [Line Items]
Revenues			128,727
Operating expenses			47,980
Operating income (loss)			80,747
Net income (loss)			74,188
Other comprehensive loss			$ 0