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Related Party Agreements and Transactions (Summary of Fees Received for Operating Pipelines for Related Parties Included in Other Income - Related Parties) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Total segment revenues and other income(1)	$ 99	$ 92	$ 86
MPC
Related Party Transaction [Line Items]
Total segment revenues and other income(1)	41	40	45
MarkWest Utica EMG
Related Party Transaction [Line Items]
Total segment revenues and other income(1)	17	17	16
Ohio Gathering
Related Party Transaction [Line Items]
Total segment revenues and other income(1)	16	16	15
Jefferson Dry Gas
Related Party Transaction [Line Items]
Total segment revenues and other income(1)	6	6	3
Sherwood Midstream
Related Party Transaction [Line Items]
Total segment revenues and other income(1)	12	8	0
Other
Related Party Transaction [Line Items]
Total segment revenues and other income(1)	$ 7	$ 5	$ 7

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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.

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No definition available.

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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_MarkWestUticaEMGMember
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Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=mpc_OhioGatheringCompanyLLCMember
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Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=mpc_MarkWestEMGJeffersonDryGasGatheringCompanyL.L.C.Member
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