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Leases - Narrative (Details) $ in Thousands | 1 Months Ended | 3 Months Ended |
--- | --- | --- | ---
Jul. 31, 2019 USD ($) ft² | Mar. 31, 2021 USD ($) | Mar. 31, 2020 USD ($) | Dec. 31, 2020 USD ($)
Operating Leased Assets [Line Items] |  |  |  |
Lessee-paid construction costs |  | $ 735 | $ 673 |
Operating lease, weighted average discount rate, percent |  | 8.90% | 8.90% |
65 Grove Street, Watertown,MA |  |  |  |
Operating Leased Assets [Line Items] |  |  |  |
Area of additional office space leased | ft² | 25,078 |  |  |
Lessee-paid construction costs | $ 800 |  |  |
Term of contract | 8 years |  |  |
Letter of credit |  |  |  |
Operating Leased Assets [Line Items] |  |  |  |
Long-term restricted cash |  | $ 1,400 |  | $ 1,400

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