| Cash, Cash Equivalents and Investments [Table Text Block] |
| | | As of September 30, 2022 | |
| | | Amortized Cost | | | Gross Unrealized Gains | | | Gross Unrealized Losses | | | Fair Value | |
| Cash, cash equivalents and restricted cash: | | | | | | | | | | | | | | | | |
| Cash | | $ | 4,533 | | | $ | — | | | $ | — | | | $ | 4,533 | |
| Money market funds | | | 113 | | | | — | | | | — | | | | 113 | |
| U.S. government agency securities | | | 7,193 | | | | — | | | | — | | | | 7,193 | |
| Commercial paper | | | 5,893 | | | | — | | | | — | | | | 5,893 | |
| Total cash, cash equivalents and restricted cash | | | 17,732 | | | | — | | | | — | | | | 17,732 | |
| | | | | | | | | | | | | | | | | |
| Short-term investments: | | | | | | | | | | | | | | | | |
| Commercial paper | | | 3,194 | | | | — | | | | — | | | | 3,194 | |
| Total short-term investments | | | 3,194 | | | | — | | | | — | | | | 3,194 | |
| Total cash, cash equivalents, restricted cash and short-term investments | | $ | 20,926 | | | $ | — | | | $ | — | | | $ | 20,926 | |
| | | As of December 31, 2021 | |
| | | Amortized Cost | | | Gross Unrealized Gains | | | Gross Unrealized Losses | | | Fair Value | |
| Cash, cash equivalents and restricted cash: | | | | | | | | | | | | | | | | |
| Cash | | $ | 1,443 | | | $ | — | | | $ | — | | | $ | 1,443 | |
| Money market funds | | | 2,822 | | | | — | | | | — | | | | 2,822 | |
| Commercial paper | | | 8,398 | | | | — | | | | — | | | | 8,398 | |
| Total cash, cash equivalents and restricted cash | | | 12,663 | | | | — | | | | — | | | | 12,663 | |
| | | | | | | | | | | | | | | | | |
| Short-term investments: | | | | | | | | | | | | | | | | |
| Commercial paper | | | 29,504 | | | | — | | | | — | | | | 29,504 | |
| Corporate debt securities | | | 9,463 | | | | — | | | | — | | | | 9,463 | |
| Total short-term investments | | | 38,967 | | | | — | | | | — | | | | 38,967 | |
| Total cash, cash equivalents, restricted cash and short-term investments | | $ | 51,630 | | | $ | — | | | $ | — | | | $ | 51,630 | |
|
| Fair Value Measurements, Recurring and Nonrecurring [Table Text Block] |
| | | As of September 30, 2022 | |
| | | Fair Value | | | Level I | | | Level II | | | Level III | |
| Assets | | | | | | | | | | | | | | | | |
| Money market funds | | $ | 113 | | | $ | 113 | | | $ | — | | | $ | — | |
| U.S. government agency securities | | | 7,193 | | | | — | | | | 7,193 | | | | — | |
| Commercial paper | | | 9,087 | | | | — | | | | 9,087 | | | | — | |
| Total assets measured at fair value | | $ | 16,393 | | | $ | 113 | | | $ | 16,280 | | | $ | — | |
| | | | | | | | | | | | | | | | | |
| Liabilities | | | | | | | | | | | | | | | | |
| Contingent put option liability | | $ | 27 | | | $ | — | | | $ | — | | | $ | 27 | |
| Total liabilities measured at fair value | | $ | 27 | | | $ | — | | | $ | — | | | $ | 27 | |
| | | As of December 31, 2021 | |
| | | Fair Value | | | Level I | | | Level II | | | Level III | |
| Assets | | | | | | | | | | | | | | | | |
| Money market funds | | $ | 2,822 | | | $ | 2,822 | | | $ | — | | | $ | — | |
| Commercial paper | | | 37,902 | | | | — | | | | 37,902 | | | | — | |
| Corporate debt securities | | | 9,463 | | | | — | | | | 9,463 | | | | — | |
| Total assets measured at fair value | | $ | 50,187 | | | $ | 2,822 | | | $ | 47,365 | | | $ | — | |
| | | | | | | | | | | | | | | | | |
| Liabilities | | | | | | | | | | | | | | | | |
| Contingent put option liability | | $ | 81 | | | $ | — | | | $ | — | | | $ | 81 | |
| Total liabilities measured at fair value | | $ | 81 | | | $ | — | | | $ | — | | | $ | 81 | |
|
| Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] |
| | | Three Months Ended September 30, 2022 | | | Nine Months Ended September 30, 2022 | |
| Fair value—beginning of period | | $ | 49 | | | $ | 81 | |
| Change in fair value of contingent put option associated with the Loan Agreement | | | (22 | ) | | | (54 | ) |
| Fair value—end of period | | $ | 27 | | | $ | 27 | |
| | | Three Months Ended September 30, 2021 | | | Nine Months Ended September 30, 2021 | |
| Fair value—beginning of period | | $ | 128 | | | $ | 246 | |
| Change in fair value of contingent put option associated with the Loan Agreement | | | (19 | ) | | | (137 | ) |
| Fair value—end of period | | $ | 109 | | | $ | 109 | |
|