Asset Retirement Obligations - Related to Acquisition (Details) - USD ($) $ in Thousands |
12 Months Ended | |
|---|---|---|
Dec. 31, 2016 |
Dec. 31, 2015 |
|
| Asset Retirement Obligations | ||
| Liabilities incurred | $ 6,947 | $ 6,349 |
| Anadarko Acquisition | ||
| Asset Retirement Obligations | ||
| Liabilities incurred | $ 6,400 | |