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Fair Value Measurments - Recurring - Significant Unobservable Inputs in Level 3 Valuation (Details) - Fair Value, Inputs, Level 3 [Member] | 6 Months Ended
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Jun. 30, 2017
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] |  |
Number Of Renewal Periods | 2 |
Embedded Derivative Renewal Term | 5 years |
Liability [Member] | Embedded derivatives in commodity contracts |  |
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] |  |
Fair Value Inputs Probability of Renewal | 50.00% | [1]
Fair Value Inputs Probability of Renewal Second Term | 75.00% | [1]
[1] | The producer counterparty to the embedded derivative has the option to renew the gas purchase agreement and the related keep-whole processing agreement for two successive five-year terms after 2022. The embedded gas purchase agreement cannot be renewed without the renewal of the related keep-whole processing agreement. Due to the significant number of years until the renewal options are exercisable and the high level of uncertainty regarding the counterparty’s future business strategy, the future commodity price environment, and the future competitive environment for midstream services in the Southern Appalachian region, management determined that a 50 percent probability of renewal for the first five-year term and 75 percent for the second five-year term are appropriate assumptions. Included in this assumption is a further extension of management’s estimates of future frac spreads through 2032.

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- Definition Represents the term for which the counterparty has the option to renew a purchase agreement related to an embedded derivative. + References No definition available. + Details
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Balance Type: | na
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- Definition [Line Items] for Schedule of the inputs used in the fair value measurement of assets and liabilities. This disclosure may include, but is not limited to, the fair value of the asset and liabilities, valuation technique used to measure fair value, the inputs used to measure fair value, the ranges of the inputs, and the weighted averages of the inputs. [Table] + References No definition available. + Details
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- Definition Represents the percentage of likelihood of renewal of the commodity contract with embedded derivative. + References No definition available. + Details
Name: | mpc_FairValueInputsProbabilityOfRenewal
Namespace Prefix: | mpc_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- Definition Represents the percentage of likelihood of renewal of the commodity contract with embedded derivative for the second term of the contract. + References No definition available. + Details
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Namespace Prefix: | mpc_
Data Type: | num:percentItemType
Balance Type: | na
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- Definition Number Of Renewal Periods + References No definition available. + Details
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- Details
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- Details
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- Details
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