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Equity-Based Compensation Plan - Additional Information (Detail) - Officer - Performance Shares [Member] - MPLX LP 2012 Incentive Compensation Plan [Member] | 3 Months Ended
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Mar. 31, 2018
Equity Transactions And Share Based Compensation [Line Items] |
Percentage paid out in cash | 25.00%
Percentage paid out in stock | 75.00%

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- Definition Equity Transactions And Share Based Compensation [Line Items] + References No definition available. + Details
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- Details
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