Agreements - CytomX (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Collaborative Agreements disclosures
Revenue from contract with customer		$ 13,287	$ 8,584
CytomX | Development milestones
Collaborative Agreements disclosures
Entitled to receive		10,000
Revenue from contract with customer				$ 3,000
CytomX | Phase 2 clinical trial
Collaborative Agreements disclosures
Revenue from contract with customer	$ 3,000
CytomX | Regulatory milestones
Collaborative Agreements disclosures
Entitled to receive		50,000
CytomX | Milestone payments
Collaborative Agreements disclosures
Entitled to receive		100,000
Milestone payments plus royalties on the commercial sales | CytomX
Collaborative Agreements disclosures
Entitled to receive		$ 160,000