EQUITY METHOD INTERESTS - Summarized Financial Information of Equity Method Investments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Schedule of Equity Method Investments [Line Items]
Operating income (loss)	$ 11,711	$ (4,942)	$ 30,352	$ (711)
Net income (loss)	$ 17,662	$ (5,498)	(9,130)	230
Equity Method Investment, Nonconsolidated Investee or Group of Investees
Schedule of Equity Method Investments [Line Items]
Revenues				46,928
Operating expenses				14,744
Operating income (loss)				32,184
Net income (loss)				32,184
Equity Method Investment, Nonconsolidated Investee or Group of Investees | Gulf Coast Express Pipeline LLC
Schedule of Equity Method Investments [Line Items]
Revenues			182,231	4,974
Operating expenses			53,359	512
Operating income (loss)			128,872	4,462
Net income (loss)			128,470	5,382
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			85,971	0
Operating expenses			83,508	7,728
Operating income (loss)			2,463	(7,728)
Net income (loss)			(16,263)	(16,653)
Other comprehensive loss			(5,037)	(9,337)
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			46	35
Operating income (loss)			(46)	(35)
Net income (loss)			480	422
Other comprehensive loss			0	$ 0
Equity Method Investment, Nonconsolidated Investee or Group of Investees | Breviloba, LLC
Schedule of Equity Method Investments [Line Items]
Revenues			83,120
Operating expenses			31,831
Operating income (loss)			51,289
Net income (loss)			46,345
Other comprehensive loss			$ 0