Revenue Recognition - Additional Information (Details)		9 Months Ended
	Jul. 27, 2020 USD ($) obligation	Sep. 30, 2020 USD ($) Option
Disaggregation Of Revenue [Line Items]
Accounts receivable		$ 0
Contract assets		0
Contract liabilities		$ 91,000,000
Reimbursement period of costs incurred for quarter ended		75 days
Number of additional customer options | Option		2
GSK
Disaggregation Of Revenue [Line Items]
Reimbursement period of costs incurred for quarter ended		75 days
GSK Collaboration Agreement
Disaggregation Of Revenue [Line Items]
Number of performance obligations | obligation	6
Transaction price	$ 108,500,000	$ 96,600,000
Pol Theta Program
Disaggregation Of Revenue [Line Items]
Reimbursement period of costs incurred for quarter ended		90 days
WRN Program
Disaggregation Of Revenue [Line Items]
Reimbursement period of costs incurred for quarter ended		75 days
Determination period of costs incurred		75 days