Collaboration Agreements (PDGFR-beta Antibody) (Details) $ in Thousands		12 Months Ended
	Mar. 31, 2016 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Collaboration Agreements [Line Items]
Accounts receivable from Bayer HealthCare		$ 175,263	$ 162,152
PDGFR-beta outside the US
Collaboration Agreements [Line Items]
Maximum percentage of outstanding shares that may be acquired, under 'standstill' provisions		20.00%
Percentage of global development cost to be paid by the collaboration partner under the collaboration		25.00%
Percentage of development cost for the territory outside the United States to be paid for under the collaboration		50.00%
Percentage of development milestone payments to be reimbursed		50.00%
Number of development milestone payments the Company received				2
Deferred Revenue, Additions				$ 2,500
Substantive milestone payment to the Company			$ 5,000
Proceeds from Collaborators				$ 25,500
Ang2 Antibody [Member]
Collaboration Agreements [Line Items]
Percentage of global development cost to be paid by the collaboration partner under the collaboration	25.00%
Percentage of development cost for the territory outside the United States to be paid for under the collaboration	50.00%
Deferred Revenue, Additions	$ 50,000
Future development milestone payment the Company is eligible to receive		$ 80,000