Properties, Plant and Equipment - Other Property, Plant and Equipment - Tabular Information (Details) - USD ($) $ in Thousands |
Dec. 31, 2016 |
Dec. 31, 2015 |
|---|---|---|
| Other Property, Plant and Equipment | ||
| Gross other property, plant and equipment | $ 8,254 | $ 8,044 |
| Less: Accumulated depreciation and amortization | (5,258) | (4,171) |
| Net other property, plant and equipment | 2,996 | 3,873 |
| Leasehold improvements | ||
| Other Property, Plant and Equipment | ||
| Gross other property, plant and equipment | 1,213 | 1,260 |
| Furniture, fixtures, computers and software | ||
| Other Property, Plant and Equipment | ||
| Gross other property, plant and equipment | 4,170 | 4,090 |
| Vehicles | ||
| Other Property, Plant and Equipment | ||
| Gross other property, plant and equipment | 1,677 | 1,537 |
| Aircraft | ||
| Other Property, Plant and Equipment | ||
| Gross other property, plant and equipment | 910 | 910 |
| Other | ||
| Other Property, Plant and Equipment | ||
| Gross other property, plant and equipment | $ 284 | $ 247 |