EQUITY METHOD INTERESTS - Rollforward Activity (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Movement In Equity Method Interests [Roll Forward]
Equity method interest, beginning balance	$ 1,258
Acquisitions	0	$ 671	$ 91
Capital contributions	327	501	0
Equity method interest, ending balance	1,555	1,258
Shin Oak Pipeline (Breviloba, LLC)
Movement In Equity Method Interests [Roll Forward]
Equity method interest, beginning balance	493
Equity method interest, ending balance		493
ALTM
Movement In Equity Method Interests [Roll Forward]
Equity method interest, beginning balance	1,258	91
Acquisitions		671
Capital contributions	327	501
Distributions	(97)	(25)
Capitalized interest	8	2
Equity income (loss), net	59	19
Accumulated other comprehensive loss		(1)
Equity method interest, ending balance	1,555	1,258	91
ALTM | Gulf Coast Express Pipeline LLC
Movement In Equity Method Interests [Roll Forward]
Equity method interest, beginning balance	291	91
Acquisitions		15
Capital contributions	2	184
Distributions	(51)	(16)
Capitalized interest	0	0
Equity income (loss), net	42	17
Accumulated other comprehensive loss		0
Equity method interest, ending balance	284	291	91
ALTM | EPIC Crude Holdings, LP
Movement In Equity Method Interests [Roll Forward]
Equity method interest, beginning balance	163	0
Acquisitions		52
Capital contributions	29	123
Distributions	0
Capitalized interest	0	0
Equity income (loss), net	(16)	(11)
Accumulated other comprehensive loss		(1)
Equity method interest, ending balance	176	163	0
ALTM | Permian Highway Pipeline LLC
Movement In Equity Method Interests [Roll Forward]
Equity method interest, beginning balance	311	0
Acquisitions		162
Capital contributions	296	147
Distributions	0
Capitalized interest	8	2
Equity income (loss), net	0	0
Accumulated other comprehensive loss		0
Equity method interest, ending balance	615	311	0
ALTM | Shin Oak Pipeline (Breviloba, LLC)
Movement In Equity Method Interests [Roll Forward]
Equity method interest, beginning balance	493	0
Acquisitions		442
Capital contributions	0	47
Distributions	(46)	(9)
Capitalized interest	0	0
Equity income (loss), net	33	13
Accumulated other comprehensive loss		0
Equity method interest, ending balance	$ 480	$ 493	$ 0