Commitments and Contingencies - MarkWest Environmental Proceeding (Details) - MarkWest Liberty Midstream Pipeline Launcher/Receiver Site - USD ($) $ in Millions |
1 Months Ended | 3 Months Ended |
|---|---|---|
Apr. 30, 2018 |
Mar. 31, 2018 |
|
| Cash | Pending Litigation | ||
| Loss Contingencies [Line Items] | ||
| Damages sought | $ 0.6 | |
| Cash | Subsequent Event | Settled Litigation | ||
| Loss Contingencies [Line Items] | ||
| Damages sought | $ 0.6 | |
| Other Liabilities | Pending Litigation | ||
| Loss Contingencies [Line Items] | ||
| Damages sought | $ 2.4 | |
| Other Liabilities | Subsequent Event | Settled Litigation | ||
| Loss Contingencies [Line Items] | ||
| Damages sought | $ 2.4 |