Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), classified as current.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Fair value of financial and nonfinancial obligations.

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Fair Value Measurements - Assets and Liabilities at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Cash equivalents and Short-term investments		$ 4,499
Fair Value, Measurements, Recurring [Member]
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total Assets	$ 32,545	37,728
Total Liabilities		125,786
Fair Value, Measurements, Recurring [Member] \| Warrant liability
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total Liabilities		6,983
Fair Value, Measurements, Recurring [Member] \| Future tranche right liability
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total Liabilities		118,803
Fair Value, Measurements, Recurring [Member] \| Cash
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Cash and Money market funds	250	250
Fair Value, Measurements, Recurring [Member] \| Money Market Funds [Member]
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Cash and Money market funds	32,295	32,979
Fair Value, Measurements, Recurring [Member] \| Short-term investments - commercial paper
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Cash equivalents and Short-term investments		3,499
Fair Value, Measurements, Recurring [Member] \| Short-term investments - U.S. treasury bills
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Cash equivalents and Short-term investments		1,000
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total Assets	32,545	33,229
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) [Member] \| Fair Value, Measurements, Recurring [Member] \| Cash
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Cash and Money market funds	250	250
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) [Member] \| Fair Value, Measurements, Recurring [Member] \| Money Market Funds [Member]
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Cash and Money market funds	$ 32,295	32,979
Significant Other Observable Inputs (Level 2) [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total Assets		4,499
Significant Other Observable Inputs (Level 2) [Member] \| Fair Value, Measurements, Recurring [Member] \| Short-term investments - commercial paper
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Cash equivalents and Short-term investments		3,499
Significant Other Observable Inputs (Level 2) [Member] \| Fair Value, Measurements, Recurring [Member] \| Short-term investments - U.S. treasury bills
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Cash equivalents and Short-term investments		1,000
Significant Unobservable Inputs (Level 3) [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total Liabilities		125,786
Significant Unobservable Inputs (Level 3) [Member] \| Fair Value, Measurements, Recurring [Member] \| Warrant liability
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total Liabilities		6,983
Significant Unobservable Inputs (Level 3) [Member] \| Fair Value, Measurements, Recurring [Member] \| Future tranche right liability
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total Liabilities		$ 118,803