Subsequent Event Subsequent Event (Detail) - Subsequent Event - USD ($) |
Apr. 29, 2018 |
Apr. 27, 2018 |
|---|---|---|
| Subsequent Event [Line Items] | ||
| Equity value | $ 23,300,000,000 | |
| Enterprise value | $ 35,600,000,000 | |
| Share price | $ 81.43 | |
| Share conversion rate | 1.87 | |
| Cash consideration to unitholders | $ 152.27 | |
| Percent paid in common stock | 85.00% | |
| Percent paid in cash | 15.00% | |
| MPC | ||
| Subsequent Event [Line Items] | ||
| Ownership of combined company | 66.00% | |
| Andeavor | ||
| Subsequent Event [Line Items] | ||
| Ownership of combined company | 34.00% |