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Derivative Financial Instruments (Embedded Derivatives in Commodity Contracts) (Details) $ in Millions | 12 Months Ended |
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Dec. 31, 2025 USD ($) | Dec. 31, 2024 USD ($)
Derivative [Line Items] |  |
Description of Embedded Derivative | MPLX has a natural gas purchase commitment embedded in a keep-whole processing agreement with a producer customer in the Southern Appalachia region expiring in December 2027. The customer has the unilateral option to extend the agreement for one five-year term through December 2032. For accounting purposes, the natural gas purchase commitment and the term extending option have been aggregated into a single compound embedded derivative. |
Embedded Derivative Financial Instruments [Member] |  |
Derivative [Line Items] |  |
Number of renewals | 1 |
Derivative, Term of Contract | 5 years |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Derivative [Line Items] |  |
Embedded Derivative, Fair Value of Embedded Derivative Liability | $ 41 | $ 58

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