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Related Party Agreements and Transactions - Employee Services Agreements (Detail) - MPC - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Related Party Transaction [Line Items]
Expenses incurred under employee services agreements	$ 138	$ 117
Rental cost of sales - related parties
Related Party Transaction [Line Items]
Expenses incurred under employee services agreements	1	0
Purchases - related parties
Related Party Transaction [Line Items]
Expenses incurred under employee services agreements	114	92
General and administrative expenses
Related Party Transaction [Line Items]
Expenses incurred under employee services agreements	$ 23	$ 25

X

- Definition

The aggregate amount of expenditures for salaries, wages, profit sharing and incentive compensation, and other employee benefits, including equity-based compensation, and pension and other postretirement benefit expense.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.4)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

+ Details

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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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- Details

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