Leases (Details) $ in Thousands			1 Months Ended	12 Months Ended
	Nov. 11, 2019 USD ($) ft²	Mar. 13, 2019 USD ($) ft²	Aug. 31, 2017 USD ($) ft²	Dec. 31, 2019 USD ($)	Jun. 30, 2020 USD ($)	Jan. 01, 2019 USD ($)
Lessee, Lease, Description [Line Items]
Right-of-use assets				$ 1,959
Operating lease, liability				2,816
Lease liabilities				1,918
Current portion of lease liability				898
Right-of-use asset, amortization term		5 years
Notice period for cancellation		3 months
Future Unreimbursed Expenditures Expected To Be Incurred				$ 3,100
Cambridge Lease
Lessee, Lease, Description [Line Items]
Office space area | ft²			13,000
Base rent			$ 832
Renewal term			5 years
Waltham Lease
Lessee, Lease, Description [Line Items]
Office space area | ft²		6,000
Base rent		$ 263
Term of contract		5 years
Vienna Lease Arrangement
Lessee, Lease, Description [Line Items]
Office space area | ft²		400
Base rent		$ 154
Term of contract		2 years
Allston Lease
Lessee, Lease, Description [Line Items]
Office space area | ft²	28,000
Renewal term	5 years
Rent-free period	180 days
Lease not yet commenced, amount	$ 1,000
Accounting Standards Update 2016-02
Lessee, Lease, Description [Line Items]
Right-of-use assets						$ 2,000
Operating lease, liability						2,500
Lease liabilities						1,900
Current portion of lease liability						613
Net deferred rent						$ (512)
Forecast | Allston Lease
Lessee, Lease, Description [Line Items]
Security deposit liability					$ 1,100