Condensed Consolidated Statements of Changes in Equity - USD ($) shares in Millions, $ in Millions		Total	Preferred Units [Member]	Preferred Partner [Member]	Units [Member]	Limited Partners [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Non-controlling Interests [Member]	Common Stock [Member]
Beginning balance, units at Dec. 31, 2018			14.0		56.1
Beginning balance at Dec. 31, 2018		$ 5,538		$ 548		$ 1,804	$ (6)	$ 3,192
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common units (in units)					0.1
Issuance of common units - net		1				1
Net income (loss)		(121)		6		(22)		(105)
Other comprehensive income (loss)		(5)					(2)	(3)
Related party contributions		1						1
Related party distributions		(51)						(51)
Other differential membership interests activity		24						24
Changes in non-economic ownership interests		(6)						(6)
Payments to Class B noncontrolling interests investors		(5)						(5)
Distributions to unitholders	[1]	(32)		(6)		(26)
Other		1						1
Ending balance, units at Mar. 31, 2019			14.0		56.2
Ending balance at Mar. 31, 2019		5,345		548		1,757	(8)	3,048
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Distributions per common unit (usd per share)									$ 0.4650
Accrued preferred distributions		$ 6
Beginning balance, units at Dec. 31, 2019		65.5	4.7		65.5
Beginning balance at Dec. 31, 2019		$ 7,066		183		2,008	(8)	4,883
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)		(720)		2		(222)		(500)
Other comprehensive income (loss)		0
Related party contributions		3						3
Related party distributions		(62)						(62)
Other differential membership interests activity		40						40
Payments to Class B noncontrolling interests investors		(10)						(10)
Distributions to unitholders	[2]	(37)		(2)		(35)
Other		$ (1)				(1)		0
Ending balance, units at Mar. 31, 2020		65.5	4.7		65.5
Ending balance at Mar. 31, 2020		$ 6,279		$ 183		$ 1,750	$ (8)	$ 4,354
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Distributions per common unit (usd per share)									$ 0.5350
Accrued preferred distributions		$ 2

[1] Distributions per common unit of $0.4650 were paid during the three months ended March 31, 2019.

[2] Distributions per common unit of $0.5350 were paid during the three months ended March 31, 2020. At March 31, 2020, $2 million of preferred unit distributions were accrued and are payable in May 2020.