Collaboration Agreements - Revenue Recognized (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Increase to the transaction price	$ (7,100)
Combined 2018 AZ Agreements
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Increase to the transaction price	5,000
Collaboration revenue | Combined 2018 AZ Agreements
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total collaboration revenue	18,371	$ 4,650	$ 45,393
Increase to the transaction price	$ 12,500