Fair Value Measurements - Assets and Liabilities Measured at Fair Value (Details) - USD ($) |
Jun. 30, 2018 |
Dec. 31, 2017 |
|---|---|---|
| Liabilities measured at fair value on a recurring basis | ||
| Warrant liability | $ 135,000 | $ 669,000 |
| Liability transfers from Level 1 to Level 2 | 0 | |
| Liability transfers from Level 2 to Level 1 | 0 | |
| Level 1 | ||
| Liabilities measured at fair value on a recurring basis | ||
| Warrant liability | 0 | 0 |
| Level 2 | ||
| Liabilities measured at fair value on a recurring basis | ||
| Warrant liability | 0 | 0 |
| Level 3 | ||
| Liabilities measured at fair value on a recurring basis | ||
| Warrant liability | $ 135,000 | $ 669,000 |