EQUITY METHOD INTERESTS - Rollforward Activity (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Movement In Equity Method Interests [Roll Forward]
Equity method interest, beginning balance	$ 1,555
Capital contributions	27	$ 286
Distributions	(128)
Equity income (loss), net	83
Accumulated other comprehensive income	1
Equity method interest, ending balance	1,538
Gulf Coast Express Pipeline, LLC
Movement In Equity Method Interests [Roll Forward]
Equity method interest, beginning balance	284
Capital contributions	0
Distributions	(37)
Equity income (loss), net	30
Accumulated other comprehensive income	0
Equity method interest, ending balance	277
EPIC Crude Holdings, LP
Movement In Equity Method Interests [Roll Forward]
Equity method interest, beginning balance	176
Capital contributions	2
Distributions	0
Equity income (loss), net	(14)
Accumulated other comprehensive income	1
Equity method interest, ending balance	165
Permian Highway Pipeline, LLC
Movement In Equity Method Interests [Roll Forward]
Equity method interest, beginning balance	615
Capital contributions	25
Distributions	(52)
Equity income (loss), net	44
Accumulated other comprehensive income	0
Equity method interest, ending balance	632
Shin Oak Pipeline (Breviloba, LLC)
Movement In Equity Method Interests [Roll Forward]
Equity method interest, beginning balance	480
Capital contributions	0
Distributions	(39)
Equity income (loss), net	23
Accumulated other comprehensive income	0
Equity method interest, ending balance	$ 464