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Related Party Agreements and Transactions - Other Income - Related Parties (Detail) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2017 | Jun. 30, 2016 | Jun. 30, 2017 | Jun. 30, 2016
Related Party Transaction [Line Items] |  |  |  |
Other income - related parties | $ 25 | $ 24 | $ 47 | $ 45
MPC |  |  |  |
Related Party Transaction [Line Items] |  |  |  |
Other income - related parties | 10 | 12 | 21 | 26
MarkWest Utica EMG [Member] |  |  |  |
Related Party Transaction [Line Items] |  |  |  |
Other income - related parties | 4 | 5 | 8 | 7
Ohio Gathering Company, LLC [Member] |  |  |  |
Related Party Transaction [Line Items] |  |  |  |
Other income - related parties | 4 | 3 | 8 | 7
Other [Member] |  |  |  |
Related Party Transaction [Line Items] |  |  |  |
Other income - related parties | $ 7 | $ 4 | $ 10 | $ 5

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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_RelatedPartyTransactionLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Reflects the sum of all other revenue and income realized from sales and other transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party during the period. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Details
Name: | us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=mpc_MarathonPetroleumCorporationMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=mpc_MarkWestUticaEMGMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=mpc_OhioGatheringCompanyLLCMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=us-gaap_OtherAffiliatesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |