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Acquisition of HST, WHC & MPLXT (Details) bbl in Millions, $ in Millions |  |  | 3 Months Ended
--- | --- | --- | ---
Sep. 01, 2017 | Mar. 01, 2017 USD ($) mi shares bbl | Mar. 31, 2018 USD ($) shares | Sep. 30, 2017 USD ($) | Mar. 31, 2017 USD ($)
Business Acquisition [Line Items] |  |  |  |  |  |
Units acquired | [1] |  |  | 113,888,889 |  |
General partner ownership interest |  | 2.00% | 2.00% | 2.00% |  |
Contribution from MPC | $ |  |  |  | $ 1,046 |  | $ 12
Number of natural gas liquids storage caverns |  |  | 8 |  |  |
Number of light product terminals |  |  | 62 |  |  |
General Partner Units |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |
Units acquired | [1] |  |  | 2,277,778 |  |
Limited Partners Common Units |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |
Units acquired | [1] |  |  | 111,611,111 |  |
HST & WHC & MPLXT |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |
Equity interest issued or issuable, value assigned | $ |  |  | $ 504 |  |  |
Equity interest issued or issuable, fair value assigned | $ |  |  | 503 |  |  |
HST & WHC & MPLXT | Cash and Cash Equivalents [Member] |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |
Payments to acquire businesses, gross | $ |  |  | $ 1,500 |  |  |
HST & WHC & MPLXT | General Partner Units |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |
Units acquired |  |  | 264,497 |  |  |
HST & WHC & MPLXT | General Partner Common Units |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |
Units acquired |  |  | 9,197,900 |  |  |
MPLX Logistics LLC | HST & WHC & MPLXT | Limited Partners Common Units |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |
Units acquired |  |  | 2,630,427 |  |  |
MPLX Holdings Inc | HST & WHC & MPLXT | Limited Partners Common Units |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |
Units acquired |  |  | 1,132,049 |  |  |
Natural gas liquids storage caverns [Member] |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |
Storage Capacity | bbl |  |  | 1.8 |  |  |
Light-product terminal [Member] |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |
Storage Capacity | bbl |  |  | 23.6 |  |  |
Refined Products [Member] |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |
Miles of pipeline | mi |  |  | 430 |  |  |
Crude Oil [Member] |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |
Miles of pipeline | mi |  |  | 174 |  |  |
Wholly Owned Properties [Member] |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |
Number of light product terminals |  |  | 59 |  |  |
Property Subject to Operating Lease [Member] |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |
Number of light product terminals |  |  | 1 |  |  |
Partially Owned Properties [Member] |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |
Number of light product terminals |  |  | 2 |  |  |
MPC |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |
Contribution from MPC | $ |  |  | $ 6 |  | $ 10 |
[1] | MPC agreed to waive approximately one-third of the first quarter 2018 distributions on the common units issued in connection with this transaction. As a result of this waiver, MPC will not receive $23.7 million of the distributions that would have otherwise accrued on such common units with respect to the first quarter 2018. See Note 4 for information regarding this acquisition.

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