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Segment Information - Additional Information (Detail) $ in Millions |  | 3 Months Ended
--- | --- | ---
Feb. 01, 2018 USD ($) | Mar. 31, 2018 USD ($) Segment refinery | Mar. 31, 2017 USD ($)
Segment Reporting Information [Line Items] |  |  |
Number of reportable segments | Segment |  | 3 |
Number of refineries | refinery |  | 6 |
Income from operations |  | $ 440 | $ 291
Refining & Marketing |  |  |
Segment Reporting Information [Line Items] |  |  |
Income from operations | $ (181) |  |
Midstream |  |  |
Segment Reporting Information [Line Items] |  |  |
Income from operations | $ 181 |  |

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- Definition Number of Refineries + References No definition available. + Details
Name: | mpc_NumberofRefineries
Namespace Prefix: | mpc_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

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- Definition Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements. + References No definition available. + Details
Name: | us-gaap_NumberOfReportableSegments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition The net result for the period of deducting operating expenses from operating revenues. + References No definition available. + Details
Name: | us-gaap_OperatingIncomeLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_SegmentReportingInformationLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=mpc_RefiningAndMarketingMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=mpc_MidstreamMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |