Income taxes - Valuation allowance (Details) - USD ($) |
12 Months Ended | |
|---|---|---|
Dec. 31, 2021 |
Dec. 31, 2020 |
|
| Valuation Allowance [Abstract] | ||
| Valuation allowance, at beginning of year | $ 16,724,000 | $ 7,913,000 |
| Increase in valuation allowance | 2,371,000 | 8,811,000 |
| Valuation allowance, at end of year | 19,095,000 | 16,724,000 |
| Accrued interest and penalties | $ 0 | $ 0 |
| X | ||||||||||
- Definition Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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| X | ||||||||||
- Definition Amount accrued for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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| X | ||||||||||
- References No definition available.
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| X | ||||||||||
- Definition Amount of increase (decrease) in the valuation allowance for a specified deferred tax asset. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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