Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies - Additional Information (Details)

v3.19.1
Summary of Significant Accounting Policies - Additional Information (Details)
€ in Thousands
 1 Months Ended 12 Months Ended
Jun. 30, 2017
USD ($)
Dec. 31, 2018
USD ($)
Dec. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Dec. 31, 2019
USD ($)
Dec. 31, 2018
EUR (€)
Accounting Policies [Line Items]            
Restricted cash   $ 30,000        
Research and development funding arrangement, sub award granted $ 1,500          
Cost reimbursement arrangement recognition period 20 months          
Cost reimbursement arrangement recognition beginning period 2017-08          
Revenue   $ 869,000 $ 508,000 $ 0    
Type of Revenue [Extensible List]   us-gaap:GrantMember us-gaap:GrantMember us-gaap:GrantMember    
Recognized income tax positions measured at largest amount greater than percentage of being realized   50.00%        
Defined contribution plan, maximum deferral rate   3.00%        
Defined Contribution Plan, Tax Status [Extensible List]   us-gaap:QualifiedPlanMember       us-gaap:QualifiedPlanMember
Defined benefit plan, contribution by employer   $ 114,000 $ 33,000      
Inventory   0 $ 0      
Milestone payments   $ 0        
U.S. Tax Authority            
Accounting Policies [Line Items]            
Federal statutory tax rate   21.00% 34.00%      
Certificates Of Deposit            
Accounting Policies [Line Items]            
Restricted cash   $ 120,000        
Maximum            
Accounting Policies [Line Items]            
Cash, FDIC insured amount   250,000        
Cash, DGS insured amount   $ 115,000       € 100
Maximum | ASU 2016-02 | Scenario, Forecast            
Accounting Policies [Line Items]            
Right-of-use asset         $ 7,800,000  
Lease liability         7,800,000  
Minimum | ASU 2016-02 | Scenario, Forecast            
Accounting Policies [Line Items]            
Right-of-use asset         7,600,000  
Lease liability         $ 7,600,000