Annual report pursuant to Section 13 and 15(d)

Commitments and Contingencies - Leases (Details)

v3.20.1
Commitments and Contingencies - Leases (Details)
$ in Thousands
1 Months Ended
Oct. 11, 2018
ft²
$ / ft²
Nov. 30, 2017
USD ($)
ft²
Oct. 31, 2017
USD ($)
Dec. 31, 2019
USD ($)
ft²
Dec. 31, 2018
USD ($)
Dec. 31, 2017
USD ($)
Lessee, Lease, Description [Line Items]            
Deferred rent | $       $ 0 $ 3,100 $ 3,100
Chesterbrook, Pennsylvania            
Lessee, Lease, Description [Line Items]            
Number of square feet of space leased on the first floor       8,231    
Number of square feet of space leased on the second floor       40,565    
Chesterbrook, Pennsylvania | Sublease Agreements | Vanguard Group, Inc            
Lessee, Lease, Description [Line Items]            
Number of square feet of space being subleased on second floor 40,565          
Initial term of sublease 37 months          
Term of optional sublease extension 3 years          
Amount per square foot less for rent during months 2 to 13 | $ / ft² 0.50          
Amount per square foot for rent after month 14 | $ / ft² 1.00          
King of Prussia, Pennsylvania            
Lessee, Lease, Description [Line Items]            
Termination fees for cancellation of lease | $   $ 150        
Area of office and laboratory space where lease terminated   16,714        
Exton, Pennsylvania | Maximum            
Lessee, Lease, Description [Line Items]            
Termination fees for cancellation of lease | $     $ 100