Ratio applied to the conversion of Markwest shares to MPLX common units.

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- Definition

Date when the business acquisition agreement was executed, in CCYY-MM-DD format.

+ References

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- Definition

Value of equity interests (such as common shares, preferred shares, or partnership interest) issued or issuable to acquire the entity.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 30

-Section 50

-Paragraph 1

-Subparagraph (b)(4)

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- Definition

Amount of long-term debt due after one year or the normal operating cycle, if longer, assumed at the acquisition date.

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

-Publisher FASB

-Name Accounting Standards Codification

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-SubTopic 20

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-Paragraph 1

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- Definition

The amount of capital contributed by the general partner.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 272

-SubTopic 10

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6373374&loc=d3e70434-108055

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-Subparagraph (SAB TOPIC 4.F)

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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.

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MPLX LP (Pending Merger with Markwest Energy Partners, L.P.) (Details) - MPLX LP $ in Millions	Jul. 11, 2015 USD ($)	Aug. 10, 2015 USD ($)	Dec. 10, 2014 USD ($)
Noncontrolling Interest [Line Items]
General partners' contributed capital			$ 9
MarkWest
Noncontrolling Interest [Line Items]
Date of merger agreement	Jul. 11, 2015
Common units conversion ratio	1.09
Equity interest issued or issuable, value assigned		$ 13,700
Long-term debt assumed	$ 4,600
General partners' contributed capital	$ 675