Multiemployer pension plans, percentage contribution by entity.

No definition available.

Name:	mpc_MultiemployerPensionPlansPercentageContributionByEntity
Namespace Prefix:	mpc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Multiemployer pension plans, percentage funded.

+ References

No definition available.

+ Details

Name:	mpc_MultiemployerPensionPlansPercentageFunded
Namespace Prefix:	mpc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Number Of Defined Benefit Pension Or Other Postretirement Or Health Plans

+ References

No definition available.

+ Details

Name:	mpc_NumberOfDefinedBenefitPensionOrOtherPostretirementOrHealthPlans
Namespace Prefix:	mpc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

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

- Definition

Amount of contributions made to multiemployer plans by the employer. A multiemployer plan is a pension or postretirement benefit plan to which two or more unrelated employers contribute where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 80
-Section 50
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=65877416&loc=SL14450702-114947

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 80
-Section 50
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=65877416&loc=SL14450691-114947

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 80
-Section 50
-Paragraph 5
-Subparagraph (e)(1)
-URI http://asc.fasb.org/extlink&oid=65877416&loc=SL14450657-114947

+ Details

Name:	us-gaap_MultiemployerPlanPeriodContributions
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Description of the nature and effect of an increase (decrease) in the percentage of the entity's employees covered by the pension or postretirement benefit plan to which two or more unrelated employers contribute where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 80
-Section 50
-Paragraph 11
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=65877416&loc=SL14450702-114947

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 80
-Section 50
-Paragraph 6
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=65877416&loc=SL14450673-114947

+ Details

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

- Details

Name:	us-gaap_MultiemployerPlanTypeAxis=us-gaap_MultiemployerPlansPensionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MultiemployerPlanTypeAxis=us-gaap_MultiemployerPlansPostretirementBenefitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Defined Benefit Pension And Other Postretirement Plans (Multiemployee Plans) (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) Plan	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Multiemployer pension plans percentage funded	65.00%
Marathon Petroleum's contributions as a percentage of total contributions to the multi-employer pension plan, maximum	5.00%
Multiemployer Plans, Pension
Defined Benefit Plan Disclosure [Line Items]
Number of multiemployer defined benefit pension or health and welfare plan	1
Multi employer pension plans	There have been no significant changes that affect the comparability of 2016, 2015 and 2014 contributions.
Multiemployer Plans, Postretirement Benefit
Defined Benefit Plan Disclosure [Line Items]
Number of multiemployer defined benefit pension or health and welfare plan	1
MPC contributions \| $	$ 6	$ 7	$ 6