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Equity (Details) - USD ($) $ / shares in Units, $ in Millions |  |  |  |  | 3 Months Ended | 6 Months Ended
--- | --- | --- | --- | --- | --- | ---
Aug. 14, 2017 | Aug. 07, 2017 | Jul. 26, 2017 | Jul. 01, 2017 | Jun. 30, 2017 | Jun. 30, 2016 | Jun. 30, 2017 | Jun. 30, 2016
Stockholders Equity Note [Line Items] |  |  |  |  |  |  |  |  |
Limited Liability Company (LLC) or Limited Partnership (LP), Managing Member or General Partner, Ownership Interest |  |  |  |  |  |  |  | 2.00% |
Units converted | [1] |  |  |  |  |  |  | 172,063 |
Issuance of units under ATM Program |  |  |  |  |  |  |  | $ 443 | $ 321
Distributions declared (including IDRs) |  |  |  |  |  | $ 311 | $ 231 | $ 590 | $ 431
Subsequent Event [Member] |  |  |  |  |  |  |  |  |
Stockholders Equity Note [Line Items] |  |  |  |  |  |  |  |  |
Equity Instruments Conversion Date |  |  |  |  | Jul. 01, 2017 |  |  |  |
Distribution Made to Limited Partner, Declaration Date |  |  |  | Jul. 26, 2017 |  |  |  |  |
Cash distributions declared per limited partner common unit |  |  |  | $ 0.5625 |  |  |  |  |
Distributions declared (including IDRs) |  |  |  | $ 294 |  |  |  |  |
Distribution Made to Limited Partner, Distribution Date |  | Aug. 14, 2017 |  |  |  |  |  |  |
Distribution Made to Limited Partner, Date of Record |  |  | Aug. 07, 2017 |  |  |  |  |  |
ATM Program [Member] |  |  |  |  |  |  |  |  |
Stockholders Equity Note [Line Items] |  |  |  |  |  |  |  |  |
Issuance of units under the ATM Program | [2] |  |  |  |  |  |  | 12,921,085 |
Class B Units [Member] | Subsequent Event [Member] |  |  |  |  |  |  |  |  |
Stockholders Equity Note [Line Items] |  |  |  |  |  |  |  |  |
Units converted |  |  |  |  | 3,990,878 |  |  |  |
Limited Partners Common Units [Member] |  |  |  |  |  |  |  |  |
Stockholders Equity Note [Line Items] |  |  |  |  |  |  |  |  |
Units converted | [1] |  |  |  |  |  |  | 168,622 |
Cash distributions declared per limited partner common unit |  |  |  |  |  | $ 0.5625 | $ 0.5100 | $ 1.1025 | $ 1.0150
Distributions declared (including IDRs) | [3] |  |  |  |  | $ 218 | $ 172 | $ 416 | $ 328
Limited Partners Common Units [Member] | Subsequent Event [Member] |  |  |  |  |  |  |  |  |
Stockholders Equity Note [Line Items] |  |  |  |  |  |  |  |  |
Units converted |  |  |  |  | 4,350,057 |  |  |  |
Limited Partners Common Units [Member] | ATM Program [Member] |  |  |  |  |  |  |  |  |
Stockholders Equity Note [Line Items] |  |  |  |  |  |  |  |  |
Issuance of units under the ATM Program | [2] |  |  |  |  |  |  | 12,662,663 |
General Partner Units [Member] |  |  |  |  |  |  |  |  |
Stockholders Equity Note [Line Items] |  |  |  |  |  |  |  |  |
Units converted | [1] |  |  |  |  |  |  | 3,441 |
Issuance of units under ATM Program |  |  |  |  |  |  |  | $ 1 |
General Partner Units [Member] | ATM Program [Member] |  |  |  |  |  |  |  |  |
Stockholders Equity Note [Line Items] |  |  |  |  |  |  |  |  |
Issuance of units under ATM Program |  |  |  |  |  |  |  | $ 9 |
Issuance of units under the ATM Program | [2] |  |  |  |  |  |  | 258,422 |
[1] | As a result of the unit-based compensation awards issued during the period, MPLX GP contributed less than $1 million in exchange for 3,441 general partner units to maintain its two percent GP Interest.
[2] | As a result of common units issued under the ATM Program during the period, MPLX GP contributed $9 million in exchange for 258,422 general partner units to maintain its two percent GP Interest.
[3] | See Note 7 for distribution information.

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