Collaboration Agreements (Bayer HealthCare LLC) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Collaboration Agreement [Line Items]
Number of sales milestone payments the Company received	1	2
Other Collaboration Revenue	$ 123,846	$ 125,312
EYLEA
Collaboration Agreement [Line Items]
Net profit (loss) from commercialization of products under collaboration agreement	89,426	61,159
Revenue Recognition, Milestone Method, Revenue Recognized	15,000	30,000
Reimbursement of Regeneron research and development expenses	2,657	20,347
Contracts Revenue	12,912	10,932
Other Collaboration Revenue	119,995	122,438
PDGFR-beta
Collaboration Agreement [Line Items]
Reimbursement of Regeneron research and development expenses	1,254	513
Contracts Revenue	2,597	2,361
Other Collaboration Revenue	$ 3,851	$ 2,874