| Cash, Cash Equivalents and Investments [Table Text Block] |
| | | As of December 31, 2022 | |
| | | Amortized Cost | | | Gross Unrealized Gains | | | Gross Unrealized Losses | | | Fair Value | |
| Cash, cash equivalents and restricted cash: | | | | | | | | | | | | | | | | |
| Cash | | $ | 13,275 | | | $ | — | | | $ | — | | | $ | 13,275 | |
| Money market funds | | | 321 | | | | — | | | | — | | | | 321 | |
| U.S. government agency securities | | | 2,444 | | | | — | | | | — | | | | 2,444 | |
| Commercial paper | | | 4,235 | | | | — | | | | — | | | | 4,235 | |
| Total cash, cash equivalents and restricted cash | | | 20,275 | | | | — | | | | — | | | | 20,275 | |
| | | | | | | | | | | | | | | | | |
| Short-term investments: | | | | | | | | | | | | | | | | |
| Commercial paper | | | 495 | | | | — | | | | — | | | | 495 | |
| Total short-term investments | | | 495 | | | | — | | | | — | | | | 495 | |
| Total cash, cash equivalents, restricted cash and short-term investments | | $ | 20,770 | | | $ | — | | | $ | — | | | $ | 20,770 | |
| | | 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 | |
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| Fair Value Measurements, Recurring and Nonrecurring [Table Text Block] |
| | | As of December 31, 2022 | |
| | | Fair Value | | | Level I | | | Level II | | | Level III | |
| Assets | | | | | | | | | | | | | | | | |
| Money market funds | | $ | 321 | | | $ | 321 | | | $ | — | | | $ | — | |
| U.S. government agency securities | | | 2,444 | | | | — | | | | 2,444 | | | | — | |
| Commercial paper | | | 4,730 | | | | — | | | | 4,730 | | | | — | |
| Total assets measured at fair value | | $ | 7,495 | | | $ | 321 | | | $ | 7,174 | | | $ | — | |
| Liabilities | | | | | | | | | | | | | | | | |
| Warrant liability | | | 7,098 | | | | — | | | | — | | | | 7,098 | |
| Total liabilities measured at fair value | | $ | 7,098 | | | $ | — | | | $ | — | | | $ | 7,098 | |
| | | 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 | | | $ | — | |
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