Equity, Equity Activity (Details) - USD ($) $ in Millions		3 Months Ended								6 Months Ended
		Jun. 30, 2019		Mar. 31, 2019		Jun. 30, 2018		Mar. 31, 2018		Jun. 30, 2019	Jun. 30, 2018		Dec. 31, 2018
Changes in carrying amount of Equity
Balance at December 31		$ 4,590		$ 4,674		$ 4,914		$ 4,806		$ 4,674	$ 4,806
Partners Capital Contribution Other	[1]					7		16
Distributions to common and preferred unitholders (a)	[2]	(241)		(261)		(206)		(213)
Net earnings attributable to partners		160		157		148		139		317	287
Cumulative effect of accounting standard adoption								(22)
Contributions (b)		25	[1]	19	[1]	139		197
Loss attributable to Predecessors		0				(16)	[3]	(8)		0	(24)	[3]
Other				1		1		(1)
Balance at March 31		4,534		4,590		4,987		4,914		4,534	4,987
Common unitholders; 245,630,444 units issued and outstanding (245,493,184 in 2018)		3,931								3,931
Preferred unitholders; 600,000 units issued and outstanding in 2019 and 2018		603								$ 603
Predecessor Equity
Changes in carrying amount of Equity
Balance at December 31						1,481		1,292	[4]		1,292	[4]
Partners Capital Contribution Other						0	[1]	0
Distributions to common and preferred unitholders (a)						0		0
Net earnings attributable to partners						0		0
Cumulative effect of accounting standard adoption								0
Contributions (b)						139		197	[4]
Loss attributable to Predecessors						(16)		(8)	[4]
Other						0		0
Balance at March 31						1,604	[4]	1,481			1,604	[4]
Common
Changes in carrying amount of Equity
Balance at December 31		3,997				2,839		2,925			2,925
Partners Capital Contribution Other	[1]					7		16
Distributions to common and preferred unitholders (a)	[2]	241		240		(206)		(205)
Net earnings attributable to partners		150		147		138		125
Cumulative effect of accounting standard adoption								(22)
Contributions (b)		25	[1]	19	[1]	0		0
Loss attributable to Predecessors						0		0
Other				1		1		0
Balance at March 31				3,997		2,779		2,839			2,779
Common unitholders; 245,630,444 units issued and outstanding (245,493,184 in 2018)													$ 4,070
Preferred Partner
Changes in carrying amount of Equity
Balance at December 31		593				594		589			589
Partners Capital Contribution Other	[1]					0		0
Distributions to common and preferred unitholders (a)	[2]	0		21		0		(8)
Net earnings attributable to partners		10		10		10		14
Cumulative effect of accounting standard adoption								0
Contributions (b)		$ 0	[1]	0	[1]	0		0
Loss attributable to Predecessors						0		0
Other				0		0		(1)
Balance at March 31				$ 593		$ 604		$ 594			$ 604
Preferred unitholders; 600,000 units issued and outstanding in 2019 and 2018													$ 604

[1] Includes Marathon and TLGP contributions to us primarily related to reimbursements for capital spending pursuant predominantly to the Amended Omnibus Agreement and the Carson Assets Indemnity Agreement.

[2] Represents cash distributions declared and paid during the period.

[3] Adjusted to include the historical results of the Predecessors. See Note 1 for further discussion.

[4] Adjusted to include the historical results of the Predecessors. See Note 1 for further discussion.