Subsequent Event	6 Months Ended
	Jun. 30, 2020
Subsequent Events [Abstract]
Subsequent Event	Subsequent EventIn April 2019, the Company amended its lease for office space at 200 Smith Street in Waltham, Massachusetts (the Premises), to add an additional 38,003 square feet of space (the Additional Space). The initial term of the lease for the Additional Space will expire in November 2029 unless terminated earlier in accordance with the terms of the lease and the Company is entitled to two five-year options to extend the lease. The initial annual base rent for the Additional Space is approximately $1.9 million and will increase annually for a total of $18.2 million over the lease term. The Company will be required to pay its share of operating expenses, taxes, and other expenses related to the additional leased premises.In July 2020, the lease commencement date was met for the Additional Space under Accounting Standards Codification Topic 842, Leases, and will result in the addition of an operating lease asset and corresponding lease liability in the third quarter of 2020.