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MPLX LP - ATM Program (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Noncontrolling Interest [Line Items]
Net proceeds from issuance of MPLX LP common limited partners units	$ 148	$ 315
MPLX LP | ATM Program
Noncontrolling Interest [Line Items]
Net proceeds from issuance of MPLX LP common limited partners units	148
Remaining authorized issuance amount	$ 570
MPLX LP | ATM Program | Limited Partners Common Units
Noncontrolling Interest [Line Items]
Sale of units (in number of common units)	4

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Total units issued during the year due to the sale of units. All partners include general, limited and preferred partners.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 272
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6373374&loc=d3e70478-108055

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The cash inflow from the issuance of common limited partners units during the period.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Financing Activities
-URI http://asc.fasb.org/extlink&oid=6513228

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3255-108585

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