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Acquisitions and Investments - Investment in Pipeline Company (Details) bbl / d in Thousands, $ in Millions		3 Months Ended
	Feb. 15, 2017 USD ($) Quarterly_reporting_period bbl / d	Mar. 31, 2017 USD ($)
Schedule of Equity Method Investments [Line Items]
IDRs forfeited per quarter	$ 1.6
Number of quarters IDRs forfeited | Quarterly_reporting_period	12
Prorated IDRs forfeited		$ 0.8
MarEn Bakken
Schedule of Equity Method Investments [Line Items]
Cash paid to acquire equity method investments	$ 500.0
Bakken Pipeline System
Schedule of Equity Method Investments [Line Items]
Crude oil throughput | bbl / d	470
MPLX LP | MarEn Bakken
Schedule of Equity Method Investments [Line Items]
Cash paid to acquire equity method investments	$ 500.0
Equity method investments, ownership percentage	25.00%
MPLX LP | Bakken Pipeline System
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	9.20%
MPC & Enbridge Energy Partners | MarEn Bakken
Schedule of Equity Method Investments [Line Items]
Cash paid to acquire equity method investments	$ 2,000.0
MPC & Enbridge Energy Partners | Bakken Pipeline System
Schedule of Equity Method Investments [Line Items]
Percentage of ownership interest in joint venture acquired	36.75%

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Pipeline Barrels Handled

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- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=66011266&loc=d3e33918-111571

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The cash outflow associated with the purchase of or advances to an equity method investments, which are investments in joint ventures and entities in which the entity has an equity ownership interest normally of 20 to 50 percent and exercises significant influence.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3213-108585

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