Agreements - CytomX (Details) - USD ($) $ in Thousands	1 Months Ended			3 Months Ended
	Jan. 31, 2017	Feb. 29, 2016	Jan. 31, 2014	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2008
Collaborative Agreements disclosures
License and milestone fees				$ 18,730	$ 10,077
Development milestones
Collaborative Agreements disclosures
Potential milestone payments						$ 16,000
CytomX
Collaborative Agreements disclosures
Payments received under collaboration agreement		$ 13,000	$ 0
License and milestone fees	$ 12,700
Potential milestone payments			160,000
CytomX | Development milestones
Collaborative Agreements disclosures
Potential milestone payments			10,000	$ 1,000
CytomX | Regulatory milestones
Collaborative Agreements disclosures
Potential milestone payments			50,000
CytomX | Sales milestones
Collaborative Agreements disclosures
Potential milestone payments			$ 100,000