EQUITY METHOD INTERESTS - Information of Equity Method Investments (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2019 USD ($) pipeline	Dec. 31, 2018 USD ($)	Nov. 09, 2018 pipeline
Schedule of Equity Method Investments [Line Items]
Number of pipeline options exercised | pipeline				4
Number of pipeline | pipeline				5		5
Equity method interests	$ 91,100	$ 91,100		$ 1,258,048	$ 91,100
Difference between carrying amount and underlying equity				$ 29,700	$ 5,800
Movement In Equity Method Interests [Roll Forward]
Balance at December 31, 2018	91,100
Acquisitions	670,625	91,100	$ 0
Contributions	501,352	0	0
Distributions	(25,316)	0	0
Capitalized interest	2,370	8,200	7,100
Equity income (loss), net	19,069	0	$ 0
Accumulated other comprehensive loss	(1,152)
Balance at December 31, 2019	1,258,048	91,100
Gulf Coast Express Pipeline LLC
Schedule of Equity Method Investments [Line Items]
Ownership percentage				16.00%	15.00%
Equity method interests	91,100	91,100		$ 291,628	$ 91,100
Movement In Equity Method Interests [Roll Forward]
Balance at December 31, 2018	91,100
Acquisitions	15,274
Contributions	183,915
Distributions	(16,208)
Capitalized interest	0
Equity income (loss), net	17,547
Accumulated other comprehensive loss	0
Balance at December 31, 2019	291,628	91,100
Undistributed earnings	1,400
EPIC Crude Holdings, LP
Schedule of Equity Method Investments [Line Items]
Ownership percentage				15.00%	0.00%
Equity method interests	163,199	0		$ 163,199	$ 0
Movement In Equity Method Interests [Roll Forward]
Balance at December 31, 2018	0
Acquisitions	51,810
Contributions	123,750
Distributions	0
Capitalized interest	0
Equity income (loss), net	(11,209)
Accumulated other comprehensive loss	(1,152)
Balance at December 31, 2019	163,199	0
Permian Highway Pipeline
Schedule of Equity Method Investments [Line Items]
Ownership percentage				26.70%	0.00%
Equity method interests	0	0		$ 310,421	$ 0
Movement In Equity Method Interests [Roll Forward]
Balance at December 31, 2018	0
Acquisitions	161,081
Contributions	146,580
Distributions	0
Capitalized interest	2,370
Equity income (loss), net	390
Accumulated other comprehensive loss	0
Balance at December 31, 2019	310,421	0
Breviloba LLC
Schedule of Equity Method Investments [Line Items]
Ownership percentage				33.00%	0.00%
Equity method interests	492,800	0		$ 492,800	$ 0
Movement In Equity Method Interests [Roll Forward]
Balance at December 31, 2018	0
Acquisitions	442,460
Contributions	47,107
Distributions	(9,108)
Capitalized interest	0
Equity income (loss), net	12,341
Accumulated other comprehensive loss	0
Balance at December 31, 2019	492,800	$ 0
Undistributed earnings	$ 3,400