Leases - Summary of Components of Lease Expense (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)
Lease Agreements [Line Items]
Operating lease cost	$ 1,814
Total lease cost	$ 4,194
Weighted-average remaining lease term (in months)	119 months 18 days
Weighted-average discount rate	10.50%
Research and Development Expenses
Lease Agreements [Line Items]
Operating lease cost	$ 2,312
Variable lease costs	707	[1]
General and Administrative Expenses
Lease Agreements [Line Items]
Operating lease cost	899
Variable lease costs	$ 276

[1] Variable lease costs include certain additional charges for operating costs, including insurance, maintenance, taxes, utilities, and other costs incurred, which are billed based on both usage and as a percentage of the Company’s share of total square footage. Short term lease costs are immaterial.