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Equity-Based Compensation Plan - Additional Information (Detail) - Performance Shares [Member] - MPLX LP 2012 Incentive Compensation Plan [Member] | 6 Months Ended
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Jun. 30, 2017 $ / shares
Equity Transactions And Share Based Compensation [Line Items] |
Performance units grant date fair value (in USD per unit) | $ 0.90
Officer [Member] |
Equity Transactions And Share Based Compensation [Line Items] |
Share Based Compensation Arrangement By Share Based Payment Award Percentage Paid Out In Cash | 75.00%
Share Based Compensation Arrangement By Share Based Payment Award Percentage Paid Out In Stock | 25.00%

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- Definition Share Based Compensation Arrangement By Share Based Payment Award Percentage Paid Out In Stock + References No definition available. + Details
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- Definition The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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