Equity Equity, Earnings Per Unit (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended							6 Months Ended
		Jun. 30, 2019		Mar. 31, 2019	Dec. 31, 2018	Jun. 30, 2018		Mar. 31, 2018	Jun. 30, 2019		Jun. 30, 2018
Net earnings		$ 160.0				$ 132.0	[1],[2],[3]		$ 317.0		$ 263.0	[1],[2],[3],[4]
Distributions on Preferred Units (b)	[5]	0.0				(10.0)	[2]		0.0		(20.0)	[2]
Limited Partners’ Interest in Net Earnings		160.0				122.0	[2]		317.0		243.0	[2]
Distributions on common units less (greater) than earnings		$ 160.0				$ (87.0)	[2]		$ 77.0		$ (171.0)	[2]
Common units - basic		245.6				217.2			245.6		217.2
Common units - diluted	[6]	245.7				217.3			245.7		217.3
Common - basic	[7]	$ 0.65				$ 0.63			$ 1.29		$ 1.23
Common - diluted	[7]	$ 0.65				$ 0.63			$ 1.29		$ 1.23
Distribution to Partner, Waived Distribution		$ 0.0		$ 12.5	$ 15.0	$ 15.0			$ 12.5		$ 30.0
Loss attributable to Predecessors		0.0				16.0	[3]	$ 8.0	0.0		24.0	[3]
Common
Limited partners’ distributions on common units (c)	[8]	0.0	[9]			(209.0)	[2]		(240.0)	[9]	(414.0)	[2]
Distributions on common units less (greater) than earnings		160.0				(71.0)	[2]		77.0		(147.0)	[2]
GP and LP Earnings (Loss)		160.0				138.0	[2]		317.0		267.0	[2]
Loss attributable to Predecessors						0.0		$ 0.0
General Partner
Distributions on common units less (greater) than earnings	[10]	0.0				16.0	[2]		0.0		24.0	[2]
GP and LP Earnings (Loss)		$ 0.0				$ (16.0)	[2]		$ 0.0		$ (24.0)	[2]

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

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

[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.

[5] The Preferred Units entitle unitholders to receive preferred distributions on a semi-annual basis. Due to the MPLX Merger, we did not declare a distribution for the first half of 2019.

[6] Diluted net earnings per unit include the effects of potentially dilutive units on our common units, which consist of unvested phantom units.

[7] Amounts may not recalculate due to rounding of dollar and unit information.

[8] Distributions of earnings for limited partners’ common units for the three months ended June 30, 2018 is net of a $15 million waiver and the six months ended June 30, 2019 and 2018 are net of a $12.5 million and $30 million waiver, respectively, from our Sponsor. There was no waiver for the three months ended June 30, 2019 because we did not declare a distribution for the second quarter of 2019 due to the MPLX Merger.

[9] We did not declare a distribution for the second quarter of 2019 due to the MPLX Merger.

[10] We have revised the historical allocation of general partner earnings to include the Predecessors’ losses of $16 million and $24 million for the three and six months ended June 30, 2018, respectively.