Commitment and Contingencies - Additional Information (Details)	1 Months Ended		9 Months Ended
	Dec. 31, 2017 ft² Phase $ / ft²	Sep. 30, 2016	Sep. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)
Commitment And Contingencies [Line Items]
Option to extend sublease			In 2018, the Company entered into a sublease agreement for the entire leased premises, which agreement was amended in September 2021 to extend the term of the sublease by approximately two weeks to be coterminous with the original lease
Letters Of Credit And Secured By Restricted Cash
Commitment And Contingencies [Line Items]
Security deposit | $			$ 1,300,000	$ 1,300,000
Maximum
Commitment And Contingencies [Line Items]
Tenant improvement allowance | $			10,900,000
Bedford, Massachusetts
Commitment And Contingencies [Line Items]
Operating lease beginning year and month		2016-11
Operating lease expiration year and month	2027-02	2021-12
Operating lease agreements additional term		3 years
Sublease aggregate base rent obligation | $			$ 2,700,000
Office space leased | ft²	67,000
Lessee, operating lease, lease not yet commenced, renewal term	5 years
Number of phases | Phase	2
Initial annual base rent per square foot | $ / ft²	39.50
Percentage increase in initial annual base rent per square foot.	3.00%
Bedford, Massachusetts | Phase One
Commitment And Contingencies [Line Items]
Office space leased | ft²	46,000
Rent due date	2018-09
Bedford, Massachusetts | Phase Two
Commitment And Contingencies [Line Items]
Office space leased | ft²	21,000
Rent due date	2019-03