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Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Statement of Comprehensive Income [Abstract]
Actuarial changes, tax	$ 3	$ 5
Prior service costs, tax	$ (4)	$ (5)

X

- Definition

Amount of tax (expense) benefit, after reclassification adjustments, of (increase) decrease in accumulated other comprehensive (income) loss related to net prior service cost (credit) pension and other postretirement defined benefit plans.

+ References

No definition available.

+ Details

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

X

- Definition

Amount of tax expense (benefit), after reclassification adjustments, of increase (decrease) in accumulated other comprehensive income (loss) related to the net actuarial gain (loss) pension and other postretirement defined benefit plans.

+ References

No definition available.

+ Details

Name:	mpc_OtherComprehensiveIncomeLossPensionandOtherPostretirementBenefitPlansNetUnamortizedGainLossAdjustmentTax
Namespace Prefix:	mpc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- References

No definition available.

+ Details

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