Description of Business and Basis of Presentation - Additional Information (Detail) bbl in Millions |
9 Months Ended |
|---|---|
|
Sep. 30, 2015
Segment
bbl
| |
| Description Of Business And Basis Of Presentation [Line Items] | |
| Storage capacity (in number of barrels) | 1 |
| Number of segments | Segment | 1 |
| Crude Oil and Product Pipeline Systems [Member] | |
| Description Of Business And Basis Of Presentation [Line Items] | |
| Percent of the net income related to assets contributed to MPLX LP | 99.50% |
| Storage Services Butane Cavern [Member] | |
| Description Of Business And Basis Of Presentation [Line Items] | |
| Percent of the net income related to assets contributed to MPLX LP | 100.00% |