EQUITY METHOD INTERESTS - Information of Equity Method Investments (Details)	3 Months Ended
	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)	Mar. 31, 2020 USD ($) pipeline	Dec. 31, 2019 USD ($)
Schedule of Equity Method Investments [Line Items]
Number of pipeline | pipeline			4
Equity method interests	$ 1,336,810,000		$ 1,336,810,000	$ 1,258,048,000
Difference between carrying amount and underlying equity			32,800,000	29,700,000
Movement In Equity Method Interests [Roll Forward]
Balance at December 31, 2019	1,258,048,000
Contributions	82,827,000	$ 66,224,000
Distributions	(22,537,000)
Capitalized interest	3,358,000
Equity income (loss), net	16,298,000	$ 270,000
Accumulated other comprehensive loss	(1,184,000)
Balance at March 31, 2020	1,336,810,000
Retained earnings, undistributed earnings			$ 1,600,000
Gulf Coast Express Pipeline LLC
Schedule of Equity Method Investments [Line Items]
Ownership percentage			16.00%
Equity method interests	291,628,000		$ 289,541,000	291,628,000
Movement In Equity Method Interests [Roll Forward]
Balance at December 31, 2019	291,628,000
Contributions	919,000
Distributions	(13,462,000)
Capitalized interest	0
Equity income (loss), net	10,456,000
Accumulated other comprehensive loss	0
Balance at March 31, 2020	289,541,000
EPIC Crude Holdings, LP
Schedule of Equity Method Investments [Line Items]
Ownership percentage			15.00%
Equity method interests	163,199,000		$ 175,549,000	163,199,000
Movement In Equity Method Interests [Roll Forward]
Balance at December 31, 2019	163,199,000
Contributions	15,000,000
Distributions	0
Capitalized interest	0
Equity income (loss), net	(1,466,000)
Accumulated other comprehensive loss	(1,184,000)
Balance at March 31, 2020	175,549,000
Permian Highway Pipeline LLC
Schedule of Equity Method Investments [Line Items]
Ownership percentage			26.70%
Equity method interests	380,800,000		$ 380,800,000	310,421,000
Movement In Equity Method Interests [Roll Forward]
Balance at December 31, 2019	310,421,000
Contributions	66,908,000
Distributions	0
Capitalized interest	3,358,000
Equity income (loss), net	113,000
Accumulated other comprehensive loss	0
Balance at March 31, 2020	380,800,000
Breviloba, LLC
Schedule of Equity Method Investments [Line Items]
Ownership percentage			33.00%
Equity method interests	492,800,000		$ 490,920,000	$ 492,800,000
Movement In Equity Method Interests [Roll Forward]
Balance at December 31, 2019	492,800,000
Contributions	0
Distributions	(9,075,000)
Capitalized interest	0
Equity income (loss), net	7,195,000
Accumulated other comprehensive loss	0
Balance at March 31, 2020	$ 490,920,000