Agreements - Fusion (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2016
Collaborative Agreements disclosures
Revenue from contract with customer	$ 13,281,000	$ 10,928,000	$ 37,407,000	$ 40,030,000
Fusion Pharmaceuticals | Development milestones
Collaborative Agreements disclosures
Potential milestone payment					$ 15,000,000
Fusion Pharmaceuticals | Phase 2 clinical trial
Collaborative Agreements disclosures
Potential milestone payment		1,500,000		1,500,000
Fusion Pharmaceuticals | Milestone payments
Collaborative Agreements disclosures
Potential milestone payment					35,000,000
License and milestone fees
Collaborative Agreements disclosures
Revenue from contract with customer	$ 79,000	672,000	5,237,000	13,533,000
License and milestone fees | Fusion Pharmaceuticals
Collaborative Agreements disclosures
Potential milestone payment					$ 50,000,000
License and milestone fees | Fusion Pharmaceuticals | Phase 1 clinical trial
Collaborative Agreements disclosures
Revenue from contract with customer		500,000		500,000
Research and development support
Collaborative Agreements disclosures
Revenue from contract with customer		388,000	$ 68,000	1,159,000
Clinical materials revenue
Collaborative Agreements disclosures
Revenue from contract with customer		$ 1,427,000		$ 2,465,000