Collaboration Agreements (Bayer) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Collaboration Agreement [Line Items]
Other Collaboration Revenue	$ 179,592	$ 123,846
EYLEA
Collaboration Agreement [Line Items]
Net profit (loss) from commercialization of products under collaboration agreement	145,835	89,426
Revenue Recognition, Milestone Method, Revenue Recognized	0	15,000
Reimbursement of Regeneron research and development expenses	2,743	2,657
Contracts Revenue	26,492	12,912
Other Collaboration Revenue	175,070	119,995
PDGFR-beta
Collaboration Agreement [Line Items]
Reimbursement of Regeneron research and development expenses	1,896	1,254
Contracts Revenue	2,626	2,597
Other Collaboration Revenue	$ 4,522	3,851
sales achievement - $200 million
Collaboration Agreement [Line Items]
Revenue Recognition, Milestone Method, Revenue Recognized		$ 15,000