Name:	mplx_EmbeddedDerivativeRenewalTerm
Namespace Prefix:	mplx_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

[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]

No definition available.

Name:	mplx_FairValueInputsAssetsandLiabilitiesQuantitativeInformationLineItems
Namespace Prefix:	mplx_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Represents the percentage of likelihood of renewal of the commodity contract with embedded derivative.

No definition available.

Name:	mplx_FairValueInputsProbabilityOfRenewal
Namespace Prefix:	mplx_
Data Type:	dtr-types1:percentItemType
Balance Type:	na
Period Type:	duration

The average forward price on the group of price risk forward or futures contracts, such as gas futures contracts.

No definition available.

Name:	us-gaap_DerivativeAverageForwardPrice
Namespace Prefix:	us-gaap_
Data Type:	srt-types:perUnitItemType
Balance Type:	na
Period Type:	instant

The forward price on the price risk forward or futures contract, such as a gas futures contract.

No definition available.

Name:	us-gaap_DerivativeForwardPrice
Namespace Prefix:	us-gaap_
Data Type:	srt-types:perUnitItemType
Balance Type:	na
Period Type:	instant

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_EmbeddedDerivativeFinancialInstrumentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	mplx_CommodityTypeAxis=mplx_NaturalGasMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: