Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies - Additional Information (Details)

v3.20.1
Summary of Significant Accounting Policies - Additional Information (Details)
€ in Thousands
 1 Months Ended 3 Months Ended 12 Months Ended
Jun. 30, 2017
USD ($)
Mar. 31, 2019
USD ($)
Dec. 31, 2018
USD ($)
Sep. 30, 2018
USD ($)
Jun. 30, 2018
USD ($)
Mar. 31, 2018
USD ($)
Dec. 31, 2019
USD ($)
Segment
Dec. 31, 2018
USD ($)
Dec. 31, 2017
USD ($)
Dec. 31, 2019
EUR (€)
Jan. 01, 2019
USD ($)
Accounting Policies [Line Items]                      
Restricted cash     $ 30,000       $ 30,000 $ 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   $ 37,000 239,000 $ 254,000 $ 185,000 $ 191,000 $ 37,000 $ 869,000 $ 508,000    
Type of Revenue [Extensible List]             us-gaap:GrantMember us-gaap:GrantMember us-gaap:GrantMember    
Short-term investments     $ 40,000,000       $ 0 $ 40,000,000      
Recognized income tax positions measured at largest amount greater than percentage of being realized             50.00%        
Number of business segments | Segment             1        
Defined contribution plan, employee minimum percentage of total plan assets             60.00%        
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 $ 0      
Milestone payments             0        
Right-of-use asset             7,144,000        
Lease liability             $ 7,328,000        
ASU 2016-02                      
Accounting Policies [Line Items]                      
Right-of-use asset                     $ 7,600,000
Lease liability                     $ 7,800,000
U.S. Tax Authority                      
Accounting Policies [Line Items]                      
Federal statutory tax rate             21.00% 21.00% 34.00%    
Certificates Of Deposit                      
Accounting Policies [Line Items]                      
Restricted cash             $ 90,000        
Maximum                      
Accounting Policies [Line Items]                      
Cash, FDIC insured amount             250,000        
Cash, DGS insured amount             $ 112,000     € 100