Revenue Recognition - Performance Obligations - Additional Information (Details) $ in Thousands		12 Months Ended
	Jul. 27, 2020 USD ($) obligation	Dec. 31, 2020 USD ($) Option
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Reimbursement period of costs incurred for quarter ended		75 days
Number of additional customer options | Option		2
Transaction price		$ 89,291
GSK
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Reimbursement period of costs incurred for quarter ended		75 days
GSK Collaboration Agreement
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Number of performance obligations | obligation	6
Transaction price	$ 108,500
Pol Theta Program
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Reimbursement period of costs incurred for quarter ended		90 days
WRN Program
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Reimbursement period of costs incurred for quarter ended		75 days
Determination period of costs incurred		75 days