Ownership Interest In Assets Owned By Company In Affiliate

No definition available.

Name:	mpc_OwnershipInterestInAssetsOwnedByCompanyInAffiliate
Namespace Prefix:	mpc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Ownership Interest In Assets Sold By Company In Affiliate

+ References

No definition available.

+ Details

Name:	mpc_OwnershipInterestInAssetsSoldByCompanyInAffiliate
Namespace Prefix:	mpc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Proceeds From Sale Of Ownership Interest In Assets By Company In Affiliate

+ References

No definition available.

+ Details

Name:	mpc_ProceedsFromSaleOfOwnershipInterestInAssetsByCompanyInAffiliate
Namespace Prefix:	mpc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_MinorityInterestLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

+ References

No definition available.

+ Details

Name:	us-gaap_MinorityInterestOwnershipPercentageByParent
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Investing Activities

-URI http://asc.fasb.org/extlink&oid=6516133

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 13

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585

+ Details

Name:	us-gaap_PaymentsToAcquireBusinessesGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The number of units or percentage investment held in the subsidiary by the limited liability company or limited partnership.

+ References

No definition available.

+ Details

Name:	us-gaap_SubsidiaryOfLimitedLiabilityCompanyOrLimitedPartnershipOwnershipInterest
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

MPLX LP MPLX LP (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended		0 Months Ended					0 Months Ended			6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Mar. 01, 2014 MPLX Pipe Line Holdings LP	May 01, 2013 MPLX Pipe Line Holdings LP	Mar. 01, 2014 MPLX LP MPLX Revolver	Mar. 01, 2014 MPLX LP Cash and cash equivalents	Oct. 31, 2012 MPLX LP Butane Cavern	Mar. 01, 2014 MPLX LP MPLX Pipe Line Holdings LP	Jun. 30, 2014 MPLX LP General Partner and Limited Partner	Jun. 30, 2014 MPLX LP General Partner	Apr. 30, 2013 MPLX LP General Partner MPLX Pipe Line Holdings LP
Noncontrolling Interest [Line Items]
MPC's partnership interest in MPLX (in percentage)									73.60%	2.00%
Ownership interest (in percentage)								69.00%			51.00%
MPLX's partnership percent indirect interest in assets							100.00%
Additional interest sold			13.00%	5.00%
Proceeds from sale of ownership interest			$ 310	$ 100
Cash paid for acquisition	$ 42	$ 1,515			$ 270	$ 40