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Related Party Agreements and Transactions - Other Income - Related Parties (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Related Party Transaction [Line Items]
Other income - related parties	$ 23	$ 22
MPC
Related Party Transaction [Line Items]
Other income - related parties	10	11
MarkWest Utica EMG
Related Party Transaction [Line Items]
Other income - related parties	4	4
Ohio Gathering
Related Party Transaction [Line Items]
Other income - related parties	4	4
Jefferson Dry Gas
Related Party Transaction [Line Items]
Other income - related parties	1	1
Sherwood Midstream
Related Party Transaction [Line Items]
Other income - related parties	3	1
Other
Related Party Transaction [Line Items]
Other income - related parties	$ 1	$ 1

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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

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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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- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=mpc_MarathonPetroleumCorporationMember
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X

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=mpc_MarkWestUticaEMGMember
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X

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=mpc_OhioGatheringCompanyLLCMember
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- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=mpc_MarkWestEMGJeffersonDryGasGatheringCompanyL.L.C.Member
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X

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=mpc_SherwoodMidstreamMember
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- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=us-gaap_OtherAffiliatesMember
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