Summary of Significant Accounting Policies - Assets and Liabilities Measured on a Recurring Basis (Details) - USD ($) $ in Thousands |
Jun. 30, 2019 |
Dec. 31, 2018 |
---|---|---|
Assets: | ||
U.S. treasury securities | $ 19,900 | $ 29,900 |
Level 1 | ||
Assets: | ||
Money market funds (included in cash and cash equivalents) | 21,957 | 32,936 |
Total assets | 44,392 | 62,811 |
Liabilities: | ||
Common Stock warrants (included in accrued and other liabilities) | 0 | 0 |
Level 3 | ||
Assets: | ||
Money market funds (included in cash and cash equivalents) | 0 | 0 |
Total assets | 0 | 0 |
Liabilities: | ||
Common Stock warrants (included in accrued and other liabilities) | 82 | 82 |
Cash and Cash Equivalents | Level 1 | ||
Assets: | ||
U.S. treasury securities | 2,495 | 0 |
Cash and Cash Equivalents | Level 3 | ||
Assets: | ||
U.S. treasury securities | 0 | 0 |
Short-term Investments | Level 1 | ||
Assets: | ||
U.S. treasury securities | 19,940 | 29,875 |
Short-term Investments | Level 3 | ||
Assets: | ||
U.S. treasury securities | $ 0 | $ 0 |