Related Party Transactions - Other Income From Related Parties (Details) - USD ($) $ in Millions |
3 Months Ended | |
|---|---|---|
Mar. 31, 2018 |
Mar. 31, 2017 |
|
| Related Party Transaction [Line Items] | ||
| Other income from related parties | $ 13 | $ 11 |
| MarkWest Utica EMG | ||
| Related Party Transaction [Line Items] | ||
| Other income from related parties | 4 | 4 |
| Ohio Gathering | ||
| Related Party Transaction [Line Items] | ||
| Other income from related parties | 4 | 4 |
| Sherwood Midstream | ||
| Related Party Transaction [Line Items] | ||
| Other income from related parties | 3 | 1 |
| Other equity method investees | ||
| Related Party Transaction [Line Items] | ||
| Other income from related parties | $ 2 | $ 2 |