Operating Assets and Liabilities - Summary of depreciation expense (Details) - USD ($) |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
|
| Operating Assets and Liabilities | |||
| Research and development costs | $ 224,000 | $ 106,000 | $ 34,000 |
| General and administrative costs | 3,000 | 3,000 | 3,000 |
| Depreciation expense, Total | 227,000 | $ 109,000 | $ 37,000 |
| Impairment loss included in research and development costs | $ 208,000 | ||