Leases - Additional Information (Details) ft² in Thousands, $ in Millions		3 Months Ended	9 Months Ended
	Apr. 11, 2019 USD ($) ft² lease_term	Sep. 30, 2019 USD ($)	Sep. 30, 2019 USD ($)
Lessee, Lease, Description [Line Items]
Remaining lease terms			8 years
Operating lease cost		$ 3.8	$ 10.6
Cash paid for amounts included in measurement of lease liabilities		$ 2.2	$ 8.5
Weighted-average incremental borrowing rate		5.70%	5.70%
Weighted-average remaining lease term		8 years 4 months 24 days	8 years 4 months 24 days
38 Sidney Street Lease
Lessee, Lease, Description [Line Items]
Number of square feet of office space (in square feet) | ft²	13
Number of optional terms available at end of current lease term (in lease terms) | lease_term	2
Term of optional lease (in years)	5 years
Tenant improvement allowance	$ 1.0
64 Sidney Street Lease
Lessee, Lease, Description [Line Items]
Term for extension of operating lease (in years)	3 years