Significant Accounting Policies - Dependence on Major Customers (Details) - Oil and gas sales - Customer concentration |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Valero Energy Corp. | |||
| Dependence on Major Customers | |||
| Concentration risk (as a percent) | 18.00% | 22.00% | |
| ETC Field Services LLC | |||
| Dependence on Major Customers | |||
| Concentration risk (as a percent) | 24.00% | 17.00% | |
| NGL Energy Partners LP | |||
| Dependence on Major Customers | |||
| Concentration risk (as a percent) | 15.00% | 12.00% | |
| PVR Midstream | |||
| Dependence on Major Customers | |||
| Concentration risk (as a percent) | 12.00% | ||
| Plains Marketing | |||
| Dependence on Major Customers | |||
| Concentration risk (as a percent) | 37.00% | 16.00% | 10.00% |
| Monarch Natural Gas, LLC | |||
| Dependence on Major Customers | |||
| Concentration risk (as a percent) | 10.00% | ||