Collaboration Agreements (Sanofi) (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Jun. 30, 2013
Collaboration Agreement [Line Items]
Number of sales milestone payments the Company received	1	2
Licenses Revenue	$ 27,837,000	$ 7,542,000
Research and development	343,113,000	287,379,000
Revenue from Related Parties	173,356,000	130,508,000
ZALTRAP Agreement
Collaboration Agreement [Line Items]
Percentage of repayment of development balance out of profits	50.00%
Deferred Revenue, Revenue Recognized	14,900,000
Licenses Revenue	19,800,000
Net profit (loss) from commercialization of products under collaboration agreement	0	(3,212,000)
Reimbursement of Regeneron research and development expenses	686,000	1,092,000
Contracts Revenue	15,236,000	2,177,000
Revenue from Related Parties	15,922,000	57,000
Antibody Collaboration
Collaboration Agreement [Line Items]
Net profit (loss) from commercialization of products under collaboration agreement	(22,405,000)	0
Recognition of Deferred Revenue	2,561,000	3,629,000
Percentage of Trial Costs borne by collaborating party	80.00%
Percentage of Trial Costs borne by entity	20.00%
Research and development	25,000,000	23,800,000
Reimbursement of Regeneron research and development expenses	168,820,000	126,822,000
Contracts Revenue	8,458,000	0
Revenue from Related Parties	157,434,000	130,451,000
PDGF
Collaboration Agreement [Line Items]
Number of Payments the Company made		2
Other Research and Development Expense		5,000,000
Milestone payment			$ 30,000,000
Minimum [Member]
Collaboration Agreement [Line Items]
Percentage of net sales paid by the related party	15.00%
Maximum [Member]
Collaboration Agreement [Line Items]
Percentage of net sales paid by the related party	30.00%