EQUITY METHOD INTERESTS (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Dec. 31, 2018
Schedule of Equity Method Investments [Line Items]
Equity method interests	$ 209,403		$ 209,403	$ 91,100
Difference between carrying amount and underlying equity			$ 1,300	$ 5,800
Movement In Equity Method Interests [Roll Forward]
Balance at December 31, 2018	91,100
Acquisitions	51,809	$ 0
Contributions	66,224	0
Income from equity method interests	270	$ 0
Balance at March 31, 2019	209,403
Gulf Coast Express Pipeline LLC
Schedule of Equity Method Investments [Line Items]
Ownership percentage			15.00%	15.00%
Equity method interests	91,100		$ 157,594	$ 91,100
Movement In Equity Method Interests [Roll Forward]
Balance at December 31, 2018	91,100
Acquisitions	0
Contributions	66,224
Income from equity method interests	270
Balance at March 31, 2019	157,594
EPIC Crude Holdings, LP
Schedule of Equity Method Investments [Line Items]
Ownership percentage			15.00%	0.00%
Equity method interests	0		$ 51,809	$ 0
Movement In Equity Method Interests [Roll Forward]
Balance at December 31, 2018	0
Acquisitions	51,809
Contributions	0
Income from equity method interests	0
Balance at March 31, 2019	$ 51,809