Collaboration Agreements (Bayer HealthCare LLC) (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Collaboration Agreement [Line Items]
Other Collaboration Revenue	$ 135,853,000	$ 88,583,000	$ 358,460,000	$ 134,594,000
EYLEA
Collaboration Agreement [Line Items]
Net profit (loss) from commercialization of products under collaboration agreement	85,351,000	31,769,000	213,291,000	57,186,000
Revenue Recognition, Milestone Method, Revenue Recognized	30,000,000	45,000,000	75,000,000	45,000,000
Reimbursement of Regeneron research and development expenses	4,394,000	3,739,000	26,235,000	13,207,000
Contracts Revenue	12,745,000	8,075,000	34,490,000	19,201,000
Other Collaboration Revenue	132,490,000	88,583,000	349,016,000	134,594,000
PDGFR-beta
Collaboration Agreement [Line Items]
Reimbursement of Regeneron research and development expenses	518,000	0	1,657,000	0
Recognition of Deferred Revenue	2,845,000	0	7,787,000	0
Other Collaboration Revenue	$ 3,363,000	$ 0	$ 9,444,000	$ 0