Basis of Presentation and Significant Accounting Policies - Summary of Fair Values of Assets and Liabilities Measured at Fair Value on Recurring and Nonrecurring Basis (Details) - USD ($) $ in Thousands |
Jun. 30, 2019 |
Dec. 31, 2018 |
|---|---|---|
| Cash and restricted cash | $ 7,524 | $ 2,752 |
| Total assets | 7,524 | 2,752 |
| Warrants potentially settleable in cash | 123 | 263 |
| Total liabilities | 123 | 263 |
| Quoted Prices in Active Markets Level 1 [Member] | ||
| Cash and restricted cash | 7,524 | 2,752 |
| Total assets | 7,524 | 2,752 |
| Warrants potentially settleable in cash | ||
| Total liabilities | ||
| Significant Other Observable Inputs Level 2 [Member] | ||
| Cash and restricted cash | ||
| Total assets | ||
| Warrants potentially settleable in cash | ||
| Total liabilities | ||
| Unobservable Inputs Level 3 [Member] | ||
| Cash and restricted cash | ||
| Total assets | ||
| Warrants potentially settleable in cash | 123 | 263 |
| Total liabilities | $ 123 | $ 263 |