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Acquisitions and Investments - Formation of Gathering and Processing Joint Venture (Details) bbl / d in Thousands, $ in Millions |  | 3 Months Ended
--- | --- | ---
Jan. 01, 2017 USD ($) bbl / d | Mar. 31, 2018 USD ($) | Mar. 31, 2017 USD ($) | [1]
Schedule of Equity Method Investments [Line Items] |  |  |
Contribution of assets to joint venture |  | $ 0 | $ 328
Sherwood Midstream |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |
Equity method investments, ownership percentage |  | 50.00% |
Sherwood Midstream | MPLX LP |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |
Contribution of assets to joint venture | $ 134 |  |
Payments to acquire interest in joint venture | 20 |  |
Sherwood Midstream | Antero Midstream Partners L.P. |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |
Payments to acquire interest in joint venture | $ 154 |  |
Ohio Fractionation |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |
Capacity | bbl / d | 20 |  |
Ohio Fractionation | Sherwood Midstream |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |
Payments to acquire interest in joint venture | $ 126 |  |
Sherwood Midstream Holdings |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |
Equity method investments, ownership percentage |  | 81.00% |
Ownership interest In assets sold by company in affiliate |  | 6.00% |
Proceeds from sale of ownership interest in assets sold by company in affiliate |  | $ 15 |
Sherwood Midstream Holdings | Direct Ownership Interest |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |
Equity method investments, ownership percentage | 79.00% |  |
Sherwood Midstream Holdings | Indirect Ownership Interest |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |
Equity method investments, ownership percentage | 10.50% |  |
Sherwood Midstream Holdings | MPLX LP |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |
Contribution of assets to joint venture | $ 203 |  |
Fair value of assets contributed | 209 |  |
Gain on disposal of assets | $ 2 |  |
Sherwood Midstream Holdings | Sherwood Midstream |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |
Equity method investments, ownership percentage | 21.00% |  |
Payments to acquire interest in joint venture | $ 44 |  |
[1] | MarkWest’s contribution of assets to Sherwood Midstream and Sherwood Midstream Holdings. See Note 5.

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