Leases - Additional Information (Details)		1 Months Ended		12 Months Ended
	May 26, 2021 USD ($) ft²	Sep. 30, 2020 ft²	Dec. 31, 2017 ft²	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Sep. 30, 2021 USD ($)	Jan. 31, 2018 ft²
Operating Leased Assets [Line Items]
Operating lease option to terminate				true
Right of use asset				$ 20,780,000	$ 22,579,000
BMR Hampshire, LLC [Member]
Operating Leased Assets [Line Items]
Letter of credit				$ 1,700,000
Letter of credit expiration date				Aug. 31, 2033
Area of Land | ft²	41,474
Fixed lease payments				$ 55,700,000
Contribution toward the cost of construction and tenant improvements for the premises	$ 6,200,000
Term of the lease				10 years
Right of use asset							$ 0
399 Binney Street [Member]
Operating Leased Assets [Line Items]
Operating lease agreement expiration date		2029-04	2029-04
Land subject to ground leases | ft²		1,824	44,336					44,807
Letter of credit				$ 900,000
Letter of credit expiration date				Sep. 30, 2028
Fixed lease payments				$ 5,400,000	4,900,000	$ 2,600,000
Right of use asset				$ 20,780,000	$ 22,579,000
Weighted-average remaining lease term				7 years 3 months 18 days	8 years 3 months 18 days
Weighted-average discount rate				10.40%	10.40%