Debt - MPC Bank Revolving Credit Facilities (Details) - Marathon Petroleum Corporation - Bank revolving credit facility due 2022 - USD ($) $ in Millions |
Mar. 31, 2018 |
Dec. 31, 2017 |
|---|---|---|
| Letter of Credit | ||
| Debt Instrument [Line Items] | ||
| Long-term line of credit | $ 0 | |
| Line of Credit | ||
| Debt Instrument [Line Items] | ||
| Long-term debt, gross | $ 0 | $ 0 |