Agreements - CytomX (Details) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended		6 Months Ended
	Feb. 29, 2016	Jan. 31, 2014	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Collaborative Agreements disclosures
Milestone payment recorded in license and milestone fee revenue			$ 1,321	$ 31,080	$ 12,861	$ 49,810
CytomX
Collaborative Agreements disclosures
Payments received under collaboration agreement		$ 0				13,000
Milestone payment recorded in license and milestone fee revenue						12,700
Potential milestone payment	$ 160,000
CytomX | Development milestones
Collaborative Agreements disclosures
Potential milestone payment	10,000
CytomX | Phase 1 clinical trial
Collaborative Agreements disclosures
Milestone payment recorded in license and milestone fee revenue				$ 1,000		$ 1,000
CytomX | Phase 2 clinical trial
Collaborative Agreements disclosures
Potential milestone payment					$ 3,000
CytomX | Regulatory milestones
Collaborative Agreements disclosures
Potential milestone payment	50,000
CytomX | Sales milestones
Collaborative Agreements disclosures
Potential milestone payment	$ 100,000