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Summary of Significant Accounting Policies (Tables) | 9 Months Ended
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Sep. 30, 2021
Accounting Policies [Abstract] |
Schedule of Restricted Cash | Restricted Cash
(in thousands) | As of September 30, 2021 |  | As of December 31, 2020
Letter of credit security: Cambridge lease | $ | — |  |  | $ | 264 |
Letter of credit security: Waltham lease | 250 |  |  | 250 |
Letter of credit security: Vienna Austria lease | 222 |  |  | 336 |
Letter of credit security: Boston lease | 855 |  |  | 1,144 |
Total restricted cash | $ | 1,327 |  |  | $ | 1,994 |
Restricted cash included in prepaid expenses and other current assets | $ | — |  |  | $ | 264 |
Restricted cash included in other assets | $ | 1,327 |  |  | $ | 1,730 |
Schedule of Reconciliation of Cash, Cash Equivalents, and Restricted Cash | The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the condensed consolidated balance sheets to the sum of the total of amounts shown in the Company’s condensed consolidated statements of cash flows as of September 30, 2021, December 31, 2020, September 30, 2020 and December 31, 2019:
(in thousands) | September 30, 2021 |  | December 31, 2020 |  | September 30, 2020 |  | December 31, 2019
Cash and cash equivalents | $ | 76,393 |  |  | $ | 78,708 |  |  | $ | 88,812 |  |  | $ | 126,184 |
Restricted cash, current portion | — |  |  | 264 |  |  | — |  |  | — |
Restricted cash, non-current | 1,327 |  |  | 1,730 |  |  | 1,905 |  |  | 1,902 |
Total cash, cash equivalents and restricted cash | $ | 77,720 |  |  | $ | 80,702 |  |  | $ | 90,717 |  |  | $ | 128,086 |

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- Definition Tabular disclosure of compensating balance arrangements that are not agreements which legally restrict the use of cash amounts shown on the balance sheet. Includes disclosure of these arrangements and the amount involved, if determinable, for the most recent audited balance sheet required and for any subsequent unaudited balance sheet required in the notes to the financial statements. Compensating balances that are maintained under an agreement to assure future credit availability are generally disclosed in the notes to the financial statements along with the amount and terms of such agreement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SAB Topic 6.H.3) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13728-122682 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(1)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
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