Debt - MPLX Credit Agreement (Details) - MPLX LP - MPLX bank revolving credit facility due 2022 $ in Millions |
3 Months Ended |
|---|---|
|
Mar. 31, 2018
USD ($)
| |
| Debt Instrument [Line Items] | |
| Borrowings | $ 50 |
| Interest rate during period | 3.00% |
| Repayments | $ 555 |
| Remaining borrowing capacity | 2,250 |
| Letter of Credit | |
| Debt Instrument [Line Items] | |
| Long-term line of credit | 3 |
| Line of Credit | |
| Debt Instrument [Line Items] | |
| Long-term debt, gross | $ 0 |