Agreements - Viridian (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Oct. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Collaborative Agreements disclosures
Revenue from contract with customer		$ 132,299	$ 82,271	$ 53,446
License and milestone fees
Collaborative Agreements disclosures
Revenue from contract with customer		$ 63,742	$ 34,788	$ 15,280
Viridian | Development and regulatory milestones
Collaborative Agreements disclosures
Revenue from contract with customer	$ 48,000
Viridian | Milestone payments
Collaborative Agreements disclosures
Revenue from contract with customer	95,000
Viridian | License and milestone fees
Collaborative Agreements disclosures
Potential milestone payment	$ 143,000